Abstract: The effect of different solid solution treatment temperatures on secondary phase and hardness of the Gd containing stainless steel was studied. The results show that after solid solution treated in the range of 1000-1150 ℃ for 30 min, the continuous secondary phase precipitated along the grain boundary only partially melts, a large number of secondary phases are dispersed in the matrix, and the “bright white” phase is wrapped by the “gray” phase. The element composition and content of “gray” phase are relatively stable. After the solid solution treatment at 1000-1070 ℃ for 30 min, almost all the Ni of the “bright white” phase is dissolved, Gd is concentrated and enriched, its size is reduced, the “gray” phase grows large and slow, and some of the “gray” phase changes to short rod shape. When the solid solution temperature rises to 1150 ℃,while Ni dissolves in the “bright white” phase, Gd diffuses and slightly dissolves, most of the “bright white” phase disappears, the “gray” phase coarsens and spheroids. The hardness of the alloy after solid solution treatment is lower than that before solid solution treatment. With the increase of solid solution temperature, the hardness of the alloy increases.

Key words: Gd containing stainless steel, solid solution treatment, second phase, hardness