What is it about?
The gas tungsten arc welding (GTAW) is now commonly being used to join boiler and super heater tubes, generally made from dissimilar steel-alloys like P22 (2.25Cr-1Mo) and P91 (9Cr-1Mo) at modern thermal power plants. After welding, excessive hardness values of the heat affected zones (HAZs) of those dissimilar weld joints are certainly obtained due to uneven and uncontrolled cooling rates, which results in eruption of abrupt martensitic transformations. So it becomes mandatory to undergo post weld heat treatment (PWHT), but improper PWHT remains incapable to normalise the large variation in hardness along base alloys, HAZs and welding zone.
Why is it important?
This ultimately leads to cracking and failure while operating at elevated temperatures. Therefore, there is a dire need to establish an appropriately optimized post weld heat treatment process to eliminate this hazardous nuisance. The present work not only statistically studies the hardness profile of critical material zones (before and after GTAW) but also makes a successful attempt to optimize its PWHT process with 95% confidence level.
