Effect of preheating and post heating in reducing diffusible hydrogen content and hydrogen assisted cracking susceptibility of modified 9Cr–1Mo steel

Abstract

The hydrogen assisted cracking susceptibility of Modified 9Cr-1Mo steel weld is evaluated by implant test by determining lower critical stress for different preheating and combination of pre, post heating conditions. The diffusible hydrogen present in the implant specimens for different test conditions is estimated. Residual stress distribution in the weld for different heating condition is estimated using SYSWELD software. For a combination of pre + post heating at 200°C, the diffusible hydrogen content of the weld comes down to 1.17 from 4.7 mL/100g and the lower critical stress of the implant specimen increases from 250 to 370 MPa. Preheating + post heating also brings down the peak tensile residual stress level in the weld joints and lowers the cracking susceptibility.

Evaluation of Laser Lap Weldability between the Titanium Alloy Ti-6Al-4V and Aluminum Alloy 6060-T6

“…In order to reduce the number of potential weld defects, according to that reported in the literature, preheating and post-weld heating at up to 200 • C were defined based on the findings reported in the literature [24,26]. The heating was performed by subjecting the samples to an 80 A current using a machine for shield metal arc welding (SMAW), the Weldline CIARC 180.…”

“…Different post-weld heat treatments (PWHT) have been investigated to improve the mechanical performance of welded joints [23]. Chakraborty et al [24] studied the hydrogen-assisted cracking susceptibility of a modified 9Cr-1Mo steel weld with different preheating conditions and a combination of pre-and post-heating conditions, concluding that a combination of pre-and post-heating at 200 • C reduced the residual stress and cracking susceptibility (reduced diffusible hydrogen). Kose et al [25] investigated the effects of preheat treatment and PWHT on stainless steel's mechanical properties and microstructure.…”