Test for stress relief cracking susceptibility in creep resistant chromium-molybdenum steels

Sarich, Conner; Alexandrov, Boian; Benatar, Avraham; Penso, Jorge

doi:10.1080/13621718.2022.2050133

Cited by 4 publications

(2 citation statements)

References 19 publications

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“…The determination of threshold stress to crack as a function of temperature conditions and susceptible microstructural features would assist in potentially predicting time to failure in service and enable design of a PWHT procedure to mitigate SRC. At least three types of accelerated Gleeble stress relaxation tests with various materials have been developed and used by researchers to study the time to failure, usually within an 8-hour period [6,24,28,[31][32][33]. The temperature and stress/strain conditions needed for SRC to occur in 347H SS have been reported in a few studies with various test conditions [6,7,28].…”

Section: H Ss Weldability and Srcmentioning

confidence: 99%

Mechanical Failure Risk Management for In-Service CSP Nitrate Hot Tanks

Pickle,

Augustine,

2024

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Section: H Ss Weldability and Srcmentioning

confidence: 99%

Mechanical Failure Risk Management for In-Service CSP Nitrate Hot Tanks

Pickle,

Augustine,

2024

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“…SRC susceptibility test methods in general focused on characterizing the stress relaxation behavior during isothermal holding in welds, i.e., after heating to the desired test temperatures [7,13,33,34]. Some recent methods have considered stress relaxation during the heating stage, such as Fink et al [35] and Sarich et al [36], which may assist in understanding further the relaxation behavior during the PWHT or transient stage in service. While previous work contributed to a base knowledge on SRC in 347H SS HAZ with differing results, a systematic study on the effects of stress, strain and temperature on time-to-failure as a function of HAZ subzone microstructure and a methodology to reveal the detailed stress component evolution during SRC would contribute to a more comprehensive understanding of HAZ SRC sensitivity of 347H SS.…”

Section: Introductionmentioning

confidence: 99%

Stress Relaxation Cracking in 347H Stainless Steel Arc Welds: Susceptibility Evaluation of Heat-Affected Zone

Pickle,

Hong,

Augustine

et al. 2024

Metals

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Stress relaxation cracking (SRC) is considered one of the major failure mechanisms for 347H stainless steel welds at elevated service temperatures or during post weld heat treatment (PWHT), especially within the heat-affected zone (HAZ). This work focuses on the characterization of SRC susceptibility within 347H physically simulated arc welded HAZ at elevated temperatures. A four-step SRC thermomechanical test in combination with finite element modeling (FEM) of the welding and testing processes is developed to establish a susceptibility map for HAZ. The test first runs a thermal cycle with three different peak temperatures (1335, 1275, and 1150 °C) to duplicate representative HAZ subzone microstructures, followed by time-to-failure examination under a variety of pre-stress (260–600 MPa) and pre-strain conditions (0.03–0.19) as a function of reheat temperatures between 750 and 1050 °C. With the aid of FEM, SRC susceptibility maps are generated to identify the threshold stress, plastic strain, and creep strain as a function of test temperature. It was found out that HAZ subzone with a lower peak temperature (1150 °C) appears to be slightly less susceptible to SRC than the other two subzones that experienced higher peak temperatures. Generally, time-to-fracture reduces with increasing initially applied stress and strain for all test temperatures. The pre-stress thresholds decrease from about 500 to 330 MPa as the testing temperature increases from 800 to 1050 °C, while the corresponding initial plastic strain thresholds reduces from 0.15 to 0.06. The SRC susceptibility was also evaluated through the Larson–Miller Parameter (LMP) analysis as a function of plastic strain, initial stress and starting stress upon reaching the testing temperature, respectively. The 1050 °C test with a high pre-applied strain (0.1) exhibits an extremely short time to failure (t = 3 s) that lies outside the general trend in LMP analysis. Additionally, it was identified that a plastic strain above 0.07 is identified to significantly reduce the bulk creep strain tolerance to fracture and therefore increases SRC susceptibility. Hardness measurement and fractography analysis indicated that the strain aging of niobium carbonitrides and other potential phases in conjunction with intergranular precipitates contributes to an increase in microhardness and increased intergranular cracking susceptibility.

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Stress relaxation cracking susceptibility evaluation in 347H stainless steel welds

Pickle,

Hong,

Vidal

et al. 2024

Weld World

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Stress relaxation cracking (SRC) has been reported as a dominant failure mechanism for 347H stainless steel welds at elevated service temperatures, occurring in either the heat-affected zone (HAZ) or fusion zone (FZ). In this study, SRC susceptibility of physically simulated HAZ and cross-welded E347-347H stainless steel welds was studied using a four-step accelerated SRC test with a thermomechanical physical simulator. The stress and temperature range studied represents weld-induced residual stress at 150–600 MPa and post-weld heat treatment temperatures between 800 and 1050 °C. For all temperature conditions, the cross-welded samples failed at a lower critical stress threshold than the simulated HAZ. A finite element model of a 50.8-mm-thick single-V groove weld was used to generate the residual stress maps induced by a 40-pass welding procedure, which in combination with the experimental threshold stress map predicted potential SRC failure locations. Postmortem microstructural evaluations were performed to identify contributing characteristics to SRC. It was found that HAZ samples exhibited a combination of creep void development, secondary cracks with intergranular fracture near grain boundary carbides, and eutectic phases. FZ samples showed brittle fracture with cracks propagating along straight, non-tortuous interdendritic grain boundaries.

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Test for stress relief cracking susceptibility in creep resistant chromium-molybdenum steels

Cited by 4 publications

References 19 publications

Mechanical Failure Risk Management for In-Service CSP Nitrate Hot Tanks

Mechanical Failure Risk Management for In-Service CSP Nitrate Hot Tanks

Stress Relaxation Cracking in 347H Stainless Steel Arc Welds: Susceptibility Evaluation of Heat-Affected Zone

Stress relaxation cracking susceptibility evaluation in 347H stainless steel welds

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