Abstract
This study investigates the effect of Zr minor additions, with Zr content from 0.015 to 0.15 mass%, on microstructure and mechanical properties of fine-grain (65 μm) CM 247 LC superalloy. Tensile test results indicate that minor addition of Zr to fine-grain CM 247 LC can dramatically improve the yield strength at 300 K as well as both the yield strength and the elongation at 1033 K. Under creep conditions of 1033 K/725 MPa or 1200 K/345 MPa, the Zr additions drastically increased the rupture life, creep rate and elongation. The AES observation reveal that Zr may enrich at grain-boundary and boride/matrix interface and dissolve in matrix, carbide of γ′ phase. Thus, Zr may change the primary MC carbide characteristics and inhibit the script-like MC carbide formation. Moreover, Zr is apparently to increase the effects of the cohesive energy of both the precipitated phase/matrix interface and the grain boundaries, also it is beneficial to stress accommodation and retards the crack initiation and propagation.
