INFLUENCE OF REPAIR WELDING OF AGED 18NI 250 MARAGING-STEEL WELDMENTSON TENSILE AND FRACTURE PROPERTIES

The effects of repair welding on tensile strength and fracture toughne ss of aged weldments of 18 Ni 250-grade maraging steel have been studi ed. It has been established that aged weldments in the steel can be re paired and approximately 95% of the tensile strength of the initial we lds could be achieved by postrepair aging treatment. Also, the repairs had practically no effect on the fracture toughness (K(IC)) of the we ldment. These results have been discussed in terms of microstructural conditions in the various affected and unaffected zones of the initial weld. One important inference that emerges from the mechanical proper ties-microstructural correlation in the study is that K(IC) of the wel d is independent of the gross microstructural features of dendritic si ze and shapes in the ranges observed in this study. It has, however, b een cautioned that the above statement is not valid in cases in which heavy segregation occurs along the interdendritic boundaries resulting in heavily banded microstructure. This can result from faulty weld pa rameters such as excessive heat input. A second aging to recover the m echanical properties of the repaired zone has additional beneficial ef fects on tensile strengths and helps in maintaining fracture toughness to the original level of the initial weld.