Effect of Microstructural Sensitization on Mechanical Properties of a Welded Chemically Stabilized Stainless Steel Pipe

Microstructure sensitization after welding of 321H stainless steels may occur in the heat-affected zone (HAZ) of the joints welded by gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) in case of high heat input. In this study, the effect of microstructural sensitization on the mechanical behavior of a 321H sensitized steel pipe is investigated. In this regard, mechanical tests including tensile, hardness, creep, and crack tip opening displacement (CTOD) have been conducted on samples in which sensitization of the HAZ area has been proven via intergranular corrosion test. The sensitized microstructure showed that despite some significant differences between properties of welded and non-welded samples, mechanical properties such as a hardness of ~ 200 HV, a tensile strength of ~ 600 MPa, and also high creep resistance at stresses below 200 MPa and temperatures up to 700 °C are in the acceptable range as per international standards and codes. However, the CTOD examinations showed that cracks in the HAZ area of the sensitized sample could propagate with definitely lower values of stress intensity (K_IC) compared to those in a non-sensitized material.