A REVIEW OF THE EFFECT OF COLD-WORK ON RESISTANCE TO SULPHIDE STRESS CRACKING
Granta Park, Great Abington
Cambridge CB1 6AL, UK
Presented at Corrosion 2006, paper 07104
Downloaded from www.thomas-sourmail.net
Share your papers !
The specific problems associated with the use of steels in
H2S-containing environments have been extensively documented.
Perhaps the most severe problem encountered in such environments
is the occurrence of sulphide stress cracking. Years of industrial
experience and laboratory tests have helped define safe conditions for
the use of C-Mn steels in sour service. However, whether these
conditions remain for cold-worked material is not clear for the
literature. The present paper presents a critical literature survey
on the effect of plastic strain applied prior to service, on the SSC
resistance of C-Mn steels. Based on data published over the past 50
years, this review considers the problem from two points of view.
Firstly, documents are reviewed which discuss results of SSC tests of
plastically strained material. Secondly, results are reviewed which
discuss the effect of cold work on hydrogen embrittlement in a more general
manner. Conclusions are drawn on the expected severity of the impact of
strain on SSC resistance, and areas are identified where further
experimental work is required.
Keywords: sulphide stress cracking, cold-work, plastic strain,
reeling, hydrogen embrittlement
The possibility that cold work affect the resistance to sulphide
stress cracking is not unrecognised. Both references  and
 underline the detrimental effect of cold work on the
performance of C-Mn steels in sour conditions. Reference 
in particular, indicates clearly that cold working may render the
material susceptible to SSC, even with a hardness under 250 HV. Both
references suggest that cold-working above 5% deformation should be
followed by heat-treatment. It is therefore implied that plastic
deformation under 5% strain should have no significant impact on the
resistance to sulphide stress cracking of C-Mn steels. In particular,
there is no revision of the maximum hardness criterion of 250 HV. A
small pilot study carried out at TWI suggested that plastic strain
could have an adverse effect on the resistance of welds to SSC, even
when the hardness remained under 250HV. It is indeed possible that
with hardnesses close to 250HV, less than 5% strain could lead to a
risk of SSC.
While reference  indicates that `the
deleterious effect of cold work on resistance to SSC is well known',
most research publications indicate that, while well known, the effect
remains poorly understood [4,5].
One of the possible sources of confusion lies what is meant by
`effect of strain'. A number of studies have been concerned with the
impact of straining during exposure to sour environments
. In the slow strain rate test (SSRT), for example,
tensile samples are tested at strain rates about
10-7-10-4s-1 in a sour environment. There is no
disagreement, in this case, that straining has a considerable impact
on ductility and rupture stress. This is, however, of little relevance
to the present study. Similarly, the effects of prior cold work on
SSRT or similar tests are not directly relevant. Of interest are
studies highlighting the influence of prior cold work on
C-Mn steels performance in sour environments under static loading
below the yield stress.
The present literature search has been divided in two parts. In a
first part, results that are directly relevant to the SSC resistance
of cold-worked materials are considered. In a second part,
considerations are given to the mechanisms by which SSC
occurs. Sulphide stress cracking is a particular occurrence of
hydrogen embrittlement (at least for the alloys considered, and in the
test conditions envisaged), where the hydrogen is generated as part of
the cathodic corrosion reaction. In fact, some authors
 have used the term `hydrogen embrittlement' to
refer to SSC. The effect of cold work can therefore be approached from
different angles: effect of cold work on hydrogen absorption on one hand
and effect of hydrogen content on mechanical properties of the material on
the other hand.
One of the difficulties in reviewing the effect of a particular
parameter is that other parameters are often not kept identical
(environment, straining method, loading method, material
chemistry). Results are therefore often not directly comparable. In
addition, there are various methods to assess the performance of a
given material in sour service, the outputs of which are not
necessarily comparable. For example, one method applied in a number of
early studies (NACE TM0177 method B also referred to as Shell Sc)
consists of testing samples in three point bend jigs, and estimating a
`critical stress' from the deflection of the sample. This estimation
neglects the stress concentration resulting from the presence of two
small holes drilled in the samples. The quantity is therefore not an
accurate measure of the stresses within the sample, and is without
meaning when samples are loaded above their yield stress. This method
has only been used for comparison of different materials. Other
studies have reported the load as a percentage of the yield stress,
not always specifying whether the yield stress is that before or after
cold working. For these reasons, a detailed account of results
collected is presented below, followed by a discussion.
To assess the impact of rotary straightening of pipes, Baldy
 carried out tests on undeformed and cold-worked
N-80 steel, of composition indicated in table
1 and using three different material
conditions leading to different tensile properties: normalised (``N''),
normalised and tempered one hour at 621 C (``NT1''), and
normalised and tempered at 650 C (``NT2''). The hardness of the
normalised material was 24 HRc (264 HV), which is higher than would be
expected from a fully normalised microstructure for a material of this
composition (205 HV, estimated with Stecal ).
Therefore, whilst the material was clearly not fully martensitic in
the normalised condition, it was also probably not fully
pearlitic. This is also confirmed by the marked effect of tempering,
which lowered the hardness of the material by as much as 16 HRc.
Composition of the steels used in
investigations by Baldy , Asahi and Ueno
 and Asahi et al .
|Elt / wt%
||0.03Nb, 0.03Al, 0.02Ti, 0.0035N, 0.001B
||0.03Nb, 0.024Al, 0.0034N
Baldy used tensile samples loaded at a constant stress in modified
creep testing machines. The samples were placed in a solution of 0.5%
acetic acid in distilled water through which a 50/50 mixture of H2S
and CO2 was continuously bubbled. Prior to the sulphide stress
cracking tests, some of the samples had been strained to 1% strain
in tension. The results indicated that 1% cold work was sufficient
to lower the load carrying capacity of N-80 steels significantly.
The actual results from Baldy do not report a threshold stress;
instead, the occurrence of failure was recorded for different values
of applied stress (typically four samples were tested at the same
stress value). Using these data, the present author inferred a
threshold stress (highest stress at which no failure occurred in 1000
h) for the different material conditions tested. The interpretation,
however, is not straighforward. Yield stress (YS), ultimate tensile
strength (UTS) and elongation are provided, though only for the
unstrained conditions. As neither full tensile results nor YS or UTS
for strained samples are available, the actual YS of the strained
material is unknown.
The present author estimated the yield stress
after 1% straining using two methods: in the first place, the stress at
1% strain was estimated assuming a linear strain hardening between YS
and UTS over the known elongation. This is likely to underestimate the
strain hardening and therefore provided a lower bound.
In the second place, the stress-strain curves were modelled using:
where is the stress, the strain and k and n
constants. Two values of n were used (0.10 and 0.15), thought to be
the lowest and typical values respectively for steels with strength
around 600 MPa . Higher values of work
hardening were obtained with n=0.10 and it was therefore considered
reasonable to assume these values would correspond to an upper
bound. As underlined in reference , the
parameter should in principle be equal to the yield
stress, but a better fit is often obtained with values of
below the yield stress. Therefore, both k and were
calculated to obtain a 0.2% proof stress equal to the yield stress
values reported, and a stress equal to the UTS at the final elongation.
The summary of the results are given in table
2. Values of stress at 1% strain,
obtained for n=0.10, were always larger than those obtained with
n=0.15. The lowest values were those obtained from the linear
Strength of the material tested by Baldy
 in different heat-treatment conditions, and estimated
strength after straining, using two methods.
Asahi and Ueno  have carried out a similar study on
a seamless pipe material of yield stress around 700 MPa. Tests
were NACE TM0177-90 method A (constant load tensile tests) in NACE
TM0177 solution A (5% NaCl + 0.5% acetic acid, saturated with
H2S). The threshold stress was defined as that for which there was
no failure after 720 h (it is not known, unfortunately, at which
stress intervals tests were carried out, and therefore it is difficult to
estimate the uncertainty that might exist on the value of the
threshold stress). For prestrained specimens, deformation was by
tensile straining. The authors varied the strength of the material by
varying the tempering temperature between 640 and 720 C, and the
samples tempered at 700 C were strained to 3, 6 and 10% prior
to SSC testing. In this case, the authors did report the yield stress
of the strained material.
Figure 1 compares the result of both studies by
showing the effect of varying the yield strength through tempering
(variations outlined in dashed lines) and through work hardening
(individual points with indication of the degree of work-hardening). As
can be seen, while in both cases, there is a detrimental effect of
strain on the threshold stress, the conclusions
differ significantly. Baldy's work indicates that the effect of strain
on SSC susceptibility is greater than that of the corresponding increase
in strength alone. For example, the critical stress for sample NT2
following straining to 1% (indicated in figure 1
as NT2+1%) is significantly lower than that of sample
NT1; however the estimated yield stress of sample NT2+1% is
approximately equal to the that of samples NT1.
Although Asahi and Ueno  concluded that the
detrimental effect of cold-work on SSC resistance was probably caused
by an increased in yield stress, their results indicate that the
effect of strain on SSC susceptibility is less than that of the
corresponding increase in strength. In this sense, their conclusions
are opposite to those of Baldy. As can be seen in figure
1, the points for strained material lie above the
curve for the materials whose strength was varied by changes in the
Figure 1 also suggests a behaviour whereby the
threshold stress firstly increases with increasing yield strength, but
decreases beyond a given value which perhaps depends on the material
under consideration. However, it should not be assumed that the
threshold stress equals the material yield stress in this region. This
is possibly only a consequence of the fact that the investigators did
not carry out tests for stresses above the yield stress. Indeed,
investigations where loads have been allowed to exceed the yield
stress have demonstrated threshold stresses above the as-received
yield stress . Nevertheless, it appears as if
below a given value, the SSC threshold stress is at least equal to the
as-received yield stress.
Further results by Asahi et al  appear to illustrate a
rather different behaviour for a lower strength steel (450 MPa, composition
given in table 1). In this case, the
threshold stress was below the as-received yield stress. However,
following cold-working by tensile straining, the threshold stress
increased and was found to be at least equal to the new yield stress
The critical stress SSC of for N-80 and Asahi's
steels in various conditions. In Baldy's work ,
the strongest material was only normalised, while materials of lower
strength were normalised and tempered. The yield stress of the
strained material was estimated by the present author, using two
methods which provide lower and upper bounds for possible
values. The critical stress was taken, by the present author, as
being the highest stress at which no failure occurred in
1000h. Asahi and Ueno's work  provide threshold
stress and yield stress in strained conditions.
These results are surprising for a number of reasons. Firstly,
the authors demonstrate that the material investigated has a yield
point, with a Lüders strain about 3%. It is therefore surprising
that the material strained to 1% plastic strain behaves differently
from both the as-received material and the material strained to
3%. It is reasonable to expect that the material strained to 1%
will exhibit regions strained to 3% plastic strain and regions with
little or no deformation. The cracking resistance should then be
dictated by the weakest regions, which, according to the results of
the authors, are the unstrained one. One would therefore expect the
critical stress to be identical to that in the as-received samples.
Unfortunately, as is often the case in similar studies, the authors do
not report the details of their test programme and it is difficult to
comment on the significance of the increase compared to the expected
accuracy with which the critical stress is estimated. It seems
reasonable however, to suggest that the increase is well within the
uncertainty typically accompanying the determination of the critical
stress. Secondly, that the increase of strength should result in an
increase of critical stress is opposite to virtually all other results
identified in this review.
Treseder and Swanson  investigated the effect
of cold work on SSC resistance for three API steel grades J55, C75 and
X52. In this case, cold work was applied by cold rolling to 4, 8, 16
and 32% thickness reduction. Chemical composition was only provided
for the C75 tubing material (table 3).
The critical stress for the SSC of a low
strength steel as investigated by Asahi et al
. Cold work appears to result in an increase of
the critical stress.
Composition of the tubing steels used in by
Treseder and Swanson . (*) not indicated in the
reference, standard requirements are given for reference.
The tests consisted in
placing three point bend specimens, with two
drilled holes, in a solution of 0.5% acetic acid in distilled water,
saturated with H2S (Shell Sc test). In this test, of four weeks
duration, the stress in the outer fibre of the specimen was estimated
from the deflection of the specimen. As discussed earlier, because of
the presence of stress concentrators (holes) and because, in this
procedure, the stress is estimated from the deflection of the beam
whether in the elastic or plastic strain regime, this stress has
little physical meaning, making the test useful only for comparative
From a number of
experiments at different values of stress, the Sc value is determined,
where Sc is the estimated stress giving a 50% probability of
failure. Prior deformation was by cold rolling. The results obtained by
these authors are shown in figure 3. According
to the authors, a value of Sc=10 ( x 104 psi) is the lower
limit for acceptability and is the basis of the hardness limit of
235 HBN (HV) recommended by NACE (at that time). In this case
however, it was shown that some of the cold-worked materials had values
of Sc under 10, although their hardness was below 235 HBN.
Dvoracek  carried out tests on P-110 grade
heat-treated (quenched and tempered) to different strength levels and
cold-worked. The composition of the material is given in table
The effect of hardness increase (caused by cold
working), on the SSC susceptibility of three API grade
steels. Increases in hardness were obtained by cold rolling to 4, 8,
16 and 32% thickness reduction. After Treseder and Swanson
Composition of the P110 casing material used by
The tests were in distilled water
saturated with H2S (it is not clear from the text whether the
solution used for this particular set of experiments contained NaCl or
not). The samples were notched cantilever beams. The author reported a
40% reduction of the threshold stress for SSC between standard and
cold-worked samples, for materials of similar strength before
cold-working (figure 4). Unfortunately, the degree of
cold work and effect on hardness are not reported, and could not be
estimated as the details of the cold-working procedure are left
unclear. It should therefore be borne in mind that the data points for
cold-worked material in figure 4 should probably
be located further to the right, having higher yield stress values
than the corresponding initial materials.
Levesque  reported that the resistance to SSC
was most affected by the first 1% of strain, but not significantly by
further cold work up to 6% strain. Unfortunately, materials and many
experimental details are not specified.
Joosten et al  have investigated the influence of
cold work, yield strength and temperature on SSC of a quenched and
tempered grade C-90 steel, the composition of which is shown in table
The effect of cold working on the critical
stress for SSC in saturated H2S solution. After Dvoracek
. Filled circles are for unstrained material,
empty circles for cold-worked. As in Dvoracek's work, the data for
cold-worked material are shown assuming the yield stress has not
been affected. This is, however, unlikely to be correct, as
illustrated by the question marks indicating a possibly higher yield
Composition of the C90 steel used in Joosten
et al's investigation .
Tests were carried out in a solution of
distilled water with 5% sodium chloride and 0.5% glacial acetic
acid. The solution was saturated with H2S. Unstrained, 2.5% and
5% strained specimens (V-notched) were tested in three point bend at
various loads so as to determine the threshold for cracking during a
100 h exposure. In all cases, the plastic deformation was induced by
tensile straining of longitudinal sections of pipe. The reference
yield stress was that of the as-received material throughout. The
authors concluded that cold work had no detectable effect on the
threshold stress level. However, this conclusion was not a direct
observation, but was drawn from a statistical treatment of
experimental results, in which five fitting parameters were inferred
from fifteen data points. It is likely that there would be a large
uncertainty on these parameters, and therefore on the conclusion drawn
by the authors. This uncertainty was not quantified in the above
reference. Of the fifteen experimental results presented by these
authors, only two allow a direct assessment of the effect of cold
work, and these indicate either a reduction or no effect on the
More recently, a number of studies have been concerned with the effect
of cold expansion on the resistance to sulphide stress cracking of
pipes [16,17,18,19]. Mack
et al  investigated the SSC resistance of L-80
(as-received yield stress 615 MPa) and P-110 (as-received yield stress
908 MPa) pipes before and after expansion by 10 and 20%. The tests
consisted of four point bend samples loaded at 100% of their yield
stress, in NACE solution A saturated with H2S and in less severe
conditions (5% NaCl in distilled water, 2.5% H2S with balance
The results suggest an effect of straining in both materials. However,
this is not perceived in L-80 when testing in the mild sour solution,
as the material passed all the tests, or in P-110 in the 100% H2S
solution, as all the tests failed. The reference yield stress was that
of the actual material and therefore accounted for possible effect of
cold work. Interestingly, the P-110 grade showed a significant drop in
longitudinal yield stress after expansion (from 908 in the as-received
condition to 680 MPa for both 10 and 20% expanded). As the actual
yield stress was used to determine loading conditions for SSC tests,
the P-110 tubing material would have been tested at a significantly
lower stress (680 MPa compared to 908 MPa) when in the cold expanded
By contrast, the same authors only used the as-received yield stress
for determination of loading conditions in further work carried out on
P-110 material [18,19]. In this case,
tests were carried out using C-ring specimens in a solution of 5%
NaCl in distilled water (gas: 1% H2S/balance CO2) and stressed to
100% of the as-received material yield stress. The composition of the materials
investigated are given in table 6. As in
the earlier study , cold work and strain ageing
appeared to be significantly detrimental to the SSC resistance of the
material. This works also shows that, not only can failure occur as a
result of straining (in a material which would otherwise pass the
given SSC test), but also that it tends to occur faster with
increasing degree of plastic strain. These results are however reported
qualitatively as graphs with an arbitrary scale and it is therefore not possible
to exploit them further.
Outcome of SSC tests in 100% H2S (squares)
and 2.5% H2S (circles) solutions, for L-80 and P-110 pipe materials,
using data from . Empty symbols indicate a pass,
filled symbols a fail.
Chemical compositions of the steels investigated by
Mack et al and Sutter et al. All elements in wt%.
||Mack et al L-80
||615 (636 expanded 20%)
||Mack et al P-110
||908 ( 680 expanded 10 and 20%)
||Sutter et al 
||292 (440 expanded 15%)
Sutter et al  carried out a similar investigation
on a proprietary grade developed by Vallourec and Mannesman Tubes,
using C-ring specimens in NACE solution A saturated with H2S. All
specimens survived, which unfortunately does not lead to any
conclusion as to the effect of cold work on SSC resistance.
A detrimental effect of cold-work was also demonstrated by Shenton
. In this study, cross-weld four point bend
samples were taken across a girth weld after different longitudinal
straining programmes aimed at reproducing the strains developed during
reeling of pipes. These were tested in NACE solution A saturated with
H2S for 720h. Again, while the hardness and yield stress of the
material were only moderately affected by the cold work, there was a
clear detrimental effect of deformation on the resistance to SSC.
Recent work carried out at TWI  on cross-weld
samples has demonstrated that, for material having a hardness close to
the recommended maximum of 250HV, a strain of approximately 1% was
sufficient to cause failure at 90% of the parent material actual yield
stress (YS 444 MPa). By contrast, 1% strain was not sufficient to cause failure at
90% of the parent material yield stress in a material of lower
These results strongly support the view that the impact of cold work
on SSC resistance cannot be understood through work-hardening
alone. In fact, Treseder and Swanson  had
proposed, as early as 1968, that the traditional hardness criterion
was not applicable to cold-rolled steels.
There is a general agreement that the effect of cold work on SSC
resistance is detrimental and progressive. This is clearly indicated
by the results of Treseder and Swanson  or Mack
et al . While a number of studies report failures of
cold-worked materials with otherwise acceptable hardness levels, there
are not enough data in the literature to estimate quantitatively the
impact of cold work on resistance to SSC at constant (cold-worked)
hardness. In addition, very few studies have looked at the effect of
small amounts of deformation (<5%). Work carried out at TWI so far
confirmed the detrimental influence of even a small amount of plastic
strain, however, in this instance, this is limited to material having a
hardness close to the recommended maximum. In other words, it does
appear that even small amounts of plastic strain should lead to a
reconsideration of the common 250HV limit for sour service, or indeed
whether any hardness criterion is applicable.
Except where mentioned, the results discussed in the literature are
relevant to parent material rather than welds. There is no reason to
question that such results would also apply to welds, and in fact, the
effect of straining may be felt more severely because of the
heterogenous properties across a weld and the presence of
stress/strain concentration at the weld toe
. Results obtained at TWI have indicated that the
strain distribution across the weld is highly concentrated near the weld root toes,
sometime exceeding the uniform strain value by a factor 3 or more. This suggests that
values of plastic strain thought to be safe for parent material may
not be so when applied across a weld.
It is now generally agreed that SSC, at least of non-nickel bearing
low-alloy steels in severely sour environments, is only a
manifestation of hydrogen embrittlement (for example, references
 and ). Occurrences of
cracking in low-alloy nickel steels, e.g. ASTM A203,
[25,26] have been linked with anodic
dissolution rather than hydrogen embrittlement. In less severely sour
environments, some authors have suggested that degradation during slow
strain rate tests was dominated by conventional SCC (anodic
dissolution) for annealed samples of AISI 1020, while hydrogen
embrittlement was the main cause of degradation in cold-worked samples
There is a number of questions that are of interest when considering
the problem of SSC as a hydrogen embrittlement phenomenon: the effect
of cold work on hydrogen uptake, whether a change in hydrogen uptakes
translates into a change in SSC resistance, etc.
It is perhaps worth repeating here that the present review is not
concerned with the effect of plastic straining in a hydrogen charging
environment, and therefore with issues such as the effect of
dislocation movement on hydrogen entry, but rather with the effect of
plastic strain on subsequent hydrogen embrittlement sensitivity.
Even within these limitations, there is a much larger body of work on
the effect of cold work on subsequent resistance to hydrogen
embrittlement and the following does not claim to be an exhaustive
Bearing in mind that SSC in severely sour environments is a hydrogen
embrittlement phenomenon, not only the effect of cold work on
embrittlement, but also the effect of hydrogen uptake will be
The study of hydrogen in steels is often complicated by the fact that
hydrogen is present in a variety of states. The lattice solubility of
hydrogen depends on the hydrogen pressure, and follows:
where xh is the atomic fraction of hydrogen in the lattice, P
is the external hydrogen pressure and T the temperature. In standard
conditions, it is extremely low (ca
, and most of the hydrogen present in steels in
these conditions is located at traps. Traps generally refer to lattice
defects (vacancies, dislocations, grain boundaries) or microstructural
features (e.g. second phase interfaces) to which the hydrogen
binds more or less strongly. Binding enthalpies have been measured for
a variety of cases and a detailed table can be found in reference
. Traps are usually categorised as strong and weak
traps, or irreversible and reversible respectively. Hydrogen can
escape from weak traps at room temperature. Nevertheless, these weak traps slow
down the apparent diffusion of hydrogen considerably when compared to
extrapolation of high temperature measurement of lattice diffusion, as
illustrated in figure 6.
Weakly trapped and lattice hydrogen form the diffusible
hydrogen. Under normal conditions, the hydrogen lattice solubility is
so low that most of the diffusible hydrogen corresponds to weakly
By contrast, strongly trapped hydrogen can only escape the material at
higher temperatures (typically above 250 C).
Cold work results in an increase in both vacancy and dislocation
densities, and one would therefore expect the hydrogen content of a
steel to increase with cold work. Numerous studies have indeed reported such
effects. For example, Hudson and Stragand 
measured the hydrogen concentration in steels cold-worked to different
amounts, after different exposure times to an aqueous H2SO4
solution. The results indicated that not only the total hydrogen
concentration but also the rate of absorption increased significantly
with increasing amounts of cold work (figure 7).
Range of diffusivity of hydrogen as a function
of temperature, illustrating the role of reversible traps at low
temperatures. After .
Huang and Shaw  have investigated the
effect of cold work on the electrochemistry of corrosion in sour
service and found that an increase in cold work leads to an increase
in corrosion rate and potential. The current density increased for up
to 20% cold work (thickness reduction). The authors suggest that this
is due to surface alteration by the cold working process, which in
turn enhances both ad- and absorption of hydrogen
. Huang et al  have later confirmed
that cold work results in both an increase in permeability and a
decrease in diffusivity of hydrogen in steel. This implies an increase
in the `solubility' of hydrogen in the steel (since permeability is a
function of diffusion and solubility), and the authors have suggested
that cold work enhances hydrogen uptake.
Hydrogen concentration as a function of
exposure time to an aqueous H2SO4 solution. After Hudson and
Stragand . Cold work increases the amount of
hydrogen absorbed and the rate of absorption.
Recent work by Nagumo et al  has demonstrated an
effect of both the Mn content and the temperature of straining on the
resulting increase in hydrogen content (figure
8, left). Hydrogen absorption increased with plastic
straining, and more importantly, increased as the straining
temperature was decreased (figure 8, right).
There is no questioning, from the literature, that cold-worked
materials will absorb more hydrogen and will do so faster than
annealed materials. This leads to the question of whether
embrittlement and hydrogen content are correlated. Numerous results
indicate that this is the case. For example, Lucas and Robinson
 have reported a strong correlation between
threshold stress intensity and diffusible hydrogen content, as
illustrated in figure 9.
Left: effect of strain and manganese content on the
amount of hydrogen absorbed in identical conditions. Right: effect of
the temperature at which the material is strained, on the amount of hydrogen
subsequently absorbed in identical conditions. After Nagumo et al
Fuchigami et al  have made similar observations
using the reduction of area in slow strain rate tests.
Shim et al  have reported a continuous decrease
in the notch tensile strength of 4340 steel after hydrogen charging
for different lengths of time (leading to different hydrogen
content). Luppo and Ovejero-Garcia have also reported a direct
correlation between diffusible hydrogen content and embrittlement in
an ASTM A516-G60 steel . In this case however, the
result is perhaps overstated as the variations in hydrogen content
relate to microstructural differences which may therefore also
influence the results.
As stated earlier, the above does not claim to be an exhaustive
review. It does not appear to be contested, however, that there is a
direct link between diffusible hydrogen content and degree of
embrittlement. Nevertheless, it has been underlined that hydrogen was
present in a variety of states (in solution, trapped at interfaces,
etc), and the question therefore arises whether all
contribute equally to the embrittlement phenomenon.
The distinction between weak and strong traps has been introduced
earlier. It is well established that strongly trapped hydrogen does
not participate in the embrittlement phenomenon
[37,38,39] and in fact, there
have been attempts to exploit this to design steels that would be more
resistant to hydrogen embrittlement . That
embrittlement is the result of weakly trapped hydrogen has been
demonstrated in a number of studies, such as that published by Takai
et al . The latter reports no embrittlement effect
for as high as 2.9 mass ppm hydrogen strongly trapped (binding energy
kJ/mol), but a strong embrittlement effect with 0.8 mass ppm
weakly trapped hydrogen (binding energy 25 kJ/mol). The authors
suggest that weak traps could include vacancies, dislocations, grain
boundaries and ferrite/cementite interfaces.
Recent work by Nagumo et al [39,41],
Nagumo  and Fuchigami et al
 have underlined the role of vacancies in the
hygrogen embrittlement of plastically deformed steels. A number of
similar experiments were carried out on steels of different
compositions, in which the hydrogen absorption was measured after
straining to 2 or 5% plastic strain. When a 1h annealing was carried
out at 250 C after straining but prior to hydrogen charging, the
hydrogen absorption was identical to that of the unstrained
material. As this temperature is not sufficient to allow dislocation
annihilation, it was concluded that vacancies were responsible for
most of the increase in hydrogen absorption.
Work carried out on the effect of cold work on hydrogen embrittlement
consistently indicates a detrimental effect. Straining accelerates the
hydrogen uptake and increases the maximum amount that can be
absorbed. The embrittlement of samples charged with hydrogen is worse
following straining, and there is good evidence that this is
essentially the result of vacancy generation during straining.
However, it is difficult to infer, from this viewpoint, whether this
should apply to sulfide stress cracking. Hydrogen embrittlement
problems broadly fall in two categories. In the first one, hydrogen is
present in a given quantity, after welding for example. In the second,
there is a continuous entry of hydrogen, as is the case during
exposure to sour environments. The role of hydrogen trapping is clear
in the first case: embrittlement is mostly dictated by how much
of the weakly trapped hydrogen is able to diffuse to a crack tip, that is,
how much diffusible hydrogen is present in the steel.
In the second case, because there is continuous supply of hydrogen, it
is not clear whether increasing the concentration of weak traps would
be of consequence. Much speculation could be carried out on this
topic, which is out of the scope of this review. It is worth pointing
out that TWI is currently carrying out an investigation of the problem.
In this program, cross-weld samples will be strained to 1% plastic strain
at room temperature or at -50C. Four point bend tests will be
carried out in NACE solution A, at a stress level known to be close to the
threshold for the selected material after 1% straining at room temperature.
Very few studies were found that dealt with the effect of small
amounts of cold work on the performance of C-Mn steel welds in sour
service. In addition, results are not easily comparable because of
variations in experimental method and parameters.
There is a general agreement that plastic strain affects the
resistance to sulphide stress cracking, even possibly for low amounts
of strain and without significant changes in hardness.
However, available data remains scarce, in particular, few studies if any
have published sufficient details for a full examination of the mechanisms
at work. As an example, the degree of work-hardening is often not investigated,
and render difficult the isolation of any effect on the SSC resistance that
would not be related to an increase in yield stress. Also, results such as those
shown in figure 1 possibly illustrate an effect of the
microstructure, as a normalised steel seems to be affected more severely by
strain than a quenched and tempered material. It is clear that quantifying the
effect of strain on SSC resistance will require a detailed study involving not
only SSC tests, but also a caracterisation of the changes in mechanical properties
and in hydrogen absorption capacity for strained materials.
The author is grateful to TWI for authorisation to publish this work, and
to Richard Pargeter for comments and discussions.
The influence of hydrogen content on the
threshold stress intensity for steel BS4360 Gr50D, with a hardness
of 405 HV (). After .
Guideline on materials requirements for carbon and low alloy
steels for H2S-containing environments in oil and gas production.
ASM Handbook volume 11.
ASM, Metals Park OH, 1986.
H. Huang and J. D. Shaw.
Cold work effect on sulfide stress cracking of pipeline steel exposed
to sour environments.
Corr. Sci., 34:61-78, 1993.
M. W. Joosten, J. J. Murali, and J. L. Hess.
Interactive effects of cold work, yield strength and temperature on
sulfide stress corrosion cracking.
In W. B. Lisagor, T. W. Crooker, and B. N. Leis, editors, Environmentaly Assisted Cracking: Science and Engineering, pages 136-151.
ASTM, Philadelphia, 1990.
R. S. Treseder.
Oil industry experience with hydrogen embrittlement and stress
In R. N. Tuttle and R. D. Kane, editors, H2S Corrosion in Oil
and Gas Production - A Compilation of Classic Papers., pages 162-176. NACE,
M. F. Baldy.
Sulfide stress cracking of steels for API Grade N-80 tubular
Corrosion, 17:509t-513t, 1961.
P. Tarin and J. Pérez.
Stecal 3.0, 2004.
H. Asahi and M. Ueno.
Effect of cold-working on sulfide stress cracking resistance of low
alloy martensitic steels.
ISIJ, 33:1275-1280, 1993.
H. Asahi, A. Yagi, and M. Ueno.
Effect of strengthening mechanisms on sulfide stress cracking
resistance of low strength steels.
ISIJ, 33:1190-1195, 1993.
G. Beranger, G. Henry, and G. Sanz, editors.
Book of Steel.
Andover: Intercept Ltd, 1996.
C. M. Hudgins, R. L. McGlasson, P. Mehdizadeh, and W. M. Rosborough.
Hydrogen sulfide cracking of carbon and alloy steels.
Corrosion, 22:238-251, 1966.
R. Treseder and T. M. Swanson.
Factors in sulfide corrosion cracking of high strength steels.
Corrosion, 24:31-37, 1968.
L. M. Dvoracek.
Sulfide stress cracking of steels.
Corrosion, 26:177-188, 1970.
C. J. Levesque.
Secondary processing has little effect on corrosion resistance.
Petroleum Engineer International, pages 72-74, May 1983.
R. Mack, A. Filippov, L. Kendziora, and L. Ring.
In-situ expansion of casing and tubing-effect on mechanical
properties and resistance to sulfide stress cracking.
In Corrosion 2000, number Paper No. 00164. NACE, 2000.
P. Sutter, C. P. Linne, J. Leyer, B. J. Orlans-Joliet, and E. Varenne.
Development of grades for seamless expandable tubes.
In Corrosion 2001, number Paper No. 01021. NACE, 2001.
R. Mack and A. Filippov.
The effects of cold-work and strain aging on the hardness of
selected grades of OCTG and on the SSC resistance of API P-110.
In Corrosion 2002, number Paper No. 02066. NACE, 2002.
R. Mack and A. Filippov.
The effects of cold-work and strain aging on the sulfide stress
cracking resistance and mechanical properties of expanded tubular steels.
In Corrosion 2003, number Paper No. 03108. NACE, 2003.
The effect of strain rate on the susceptibility of pipeline girth
welds to sulfide stress cracking.
In Corrosion 2005, number Paper No. 05117. NACE, 2005.
Twi confidential data, 2005.
M. M. Festen, H. W. deGroot, J. W. M. Damen, and K. vanGelder.
The effect of hardness on stress-induced environmental cracking of
c-mn steels in sour environments.
In Corrosion Prevention in the Process Industries, pages
173-186, Houston, Texas, 1990. NACE, NACE.
Sulfide stress corrosion cracking of some medium and low alloy
Corrosion, 23:154-172, 1967.
B. J. Berkowitz and F. H. Heubaum.
The role of hydrogen in sulfide stress cracking in low alloy steels.
Corrosion, 40:240-245, 1984.
A. K. Dunlop.
Stress corrosion cracking of low strength, low alloy nickel steels in
Corrosion, 34:88-96, 1978.
J. G. Erlings, H. W. Groot, and J. Nauta.
The effect of slow plastic and elastic straining on sulphide stress
cracking and hydrogen embrittlement of 3.5% Ni steel and API 5L X60 steel.
Corr. Sci., 27:1153-1167, 1987.
H. Huang and W. J. D. Shaw.
Effect of cold work on the fracture of a mild steel exposed to a sour
Mater. Charact., 34:43-50, 1995.
J. P. Hirth.
Effects of hydrogen on the properties of iron and steel.
Mater. Trans. A, 11:861-890, 1980.
R. M. Hudson and G. L. Stragand.
Effect of cold drawing on hydrogen behaviour in steel.
Corrosion, 16:253t-257t, 1960.
H. Huang and J. D. Shaw.
Electrochemical aspects of cold work effect on corrosion of mild
steel in sour gas environments.
Corrosion, 48:931-939, 1992.
Y. Huang, A. Nakajima, A. Nishikata, and T. Tsuru.
Effect of mechanical deformation on permeation of hydrogen in iron.
ISIJ Int., 43:548-554, 2003.
Hydrogen related failure of steels - a new aspect.
Mater. Sci. Techn., 20:940-950, 2004.
K. A. Lucas and M. J. Robinson.
The influence of lattice hydrogen content on the hydrogen-assisted
cracking of high strength steel.
Corr. Sci., 26:705-717, 1986.
H. Fuchigami, H. Minami, and M. Nagumo.
Effect of grain size on the susceptibility of martensitic steel to
Phil. Mag. Letters, 86:21-29, 2006.
I.-O. Shim and J. G. Byrne.
A study of hydrogen embrittlement in 4340 steel, I: mechanical
Mater. Sci. Eng. A, A123:169-180, 1990.
M. I. Luppo and J. Ovejero-Garcia.
The influence of microstructure on the trapping and diffusion of
hydrogen in a low carbon steel.
Corr. Sci., 32:1125-1136, 1991.
K. Takai and R. Watanuki.
Hydrogen in trapping states innocuous to environmental degradation of
ISIJ, 43:520-526, 2003.
Function of hydrogen in embrittlement of high-strength steels.
ISIJ Int., 41:590-598, 2001.
M. Nagumo, K. Takai, and N. Okuda.
Nature of hydrogen trapping sites in steels induced by plastic
J. Alloys and Compounds, 293-295:310-316, 1999.
H. Asahi, D. Hirakami, and S. Yamasaki.
Hydrogen trapping behavior in vanadium-added steel.
ISIJ, 43:527-533, 2003.
M. Nagumo, K. Ohta, and H. Saitoh.
Deformation induced defects in iron revealed by thermal desorption
spectroscopy of tritium.
Scripta Mater., 40:313-319, 1999.
This document was generated using the
LaTeX2HTML translator Version 2002 (1.62)
Copyright © 1993, 1994, 1995, 1996,
Computer Based Learning Unit, University of Leeds.
Copyright © 1997, 1998, 1999,
Mathematics Department, Macquarie University, Sydney.
The command line arguments were:
latex2html -split 1 -title 'A review of the effect of cold-work on resistance to sulphide stress cracking' -white -noparbox_images -math_parsing -notop_navigation -nonavigation -noreuse -dir ./truc index.tex
The translation was initiated by on 2007-06-27