Degradation and anisotropy characteristics of hardness in Ni-base superalloys after precipitation phase coarsening

Ni-base superalloys were widely used in the manufacture of the hot-end components in the military and civil engineering. Coarsening of the precipitation phase usually occurs during the service of this kind of precipitate strengthened alloys, and it will induce degradation for their mechanical properties. By integrating with related finite element method (FEM) simulations and mechanism analysis, the present paper focuses on the effect of precipitation phase coarsening on the hardness of Ni-base superalloys, in which the relationship between the evolution of microstructure in the material and its macroscopic mechanical properties was analyzed in detail. After coarsening of the precipitation phase, the results demonstrate that considerable degradation occurs for the hardness of alloys, and the hardness also displays an anisotropic characteristic. In general, when the volume fraction or the coarsening's degree of precipitation phase are relatively low, the hardness of alloys increases first and then decreases gradually along with the increase of loading direction. Comparatively, in the case of high volume fraction and high coarsening's degree of precipitation phase, the hardness increases monotonously with the loading direction. The related variations of alloy hardness are correlated with the evolution of precipitation phase shape, size and distribution within the alloy. The microstructural evolution changes the manners of the nucleation, multiplication and movement of dislocations within the material, and it further leads to different macroscopic hardness. © 2022, China Science Publishing & Media Ltd. All right reserved.