コバルト基合金溶接部の粒界腐食性に及ぼす熱処理条件の影響

抄録

The influence of heat treatment conditions on intergranular corrosion (IGC) was investigated for the weldments of the Co-based alloy, Stellite by gas welding. The Stellite has IGC susceptibility when it is heated at temperatures ranging from 693 to 973K after welding. It is clarified that this IGC susceptibility of weldments which are subjected to post-weld heat treatment is due to the formation of the grainboundary Cr depletion zone which resulted from precipitation of the M₇C₃ type Cr carbides. It is also clarified that the grainboundary precipitation of the secondary complex M₂₃C₆ carbides consisting of W-Co-Cr-C which are induced by heating above around 1000K suppresses the IGC in Stellite equivalent to production because of mitigation of Cr-depleted zones formation.