微量元素Zr添加对K492M高温合金微观组织及力学性能的影响

Effect of Trace Element Zr Addition on Microstructure and Mechanical Properties of K492M Superalloy

摘要:

本文研究了微量Zr元素添加对K492M高温合金微观组织、室温和高温力学性能的影响作用。实验合金中的Zr含量在60~580 ppm范围内变化。结果表明，微量Zr元素添加并未影响铸态和热处理态K492M合金的主要相组成，铸态K492M合金主要由γ基体相、γ'沉淀相、MC型碳化物和(γ+γ')共晶相组成，热处理后(γ+γ')共晶相基本消失，析出M23C6型碳化物。微量Zr元素添加显著细化K492M合金的晶粒组织，当Zr含量为160 ppm时，铸态和热处理态合金的晶粒组织细化效果最为显著。随着Zr含量由60 ppm增加至580 ppm，铸态和热处理态K492M合金中MC碳化物趋于细化；Zr元素添加对合金中γ′相体积分数及尺寸影响较小。Zr元素含量变化对热处理态K492M合金的室温拉伸性能及高温（760 ℃）拉伸强度影响较小，但显著影响合金的高温塑性和持久性能（760 ℃/662 MPa），Zr含量为160 ppm时，合金的高温拉伸延伸率及持久寿命最高，相比于含0 ppm Zr的合金分别提高了53.8%和16.8%。

Abstract:

The influence of trace Zr element addition on the microstructure, room temperature and high-temperature mechanical properties of K492M superalloy was studied. The Zr content in the experimental alloys ranged from 60 ppm to 580 ppm. The results indicate that the addition of Zr element did not change the main phase constitution of the as-cast and heat-treated K492M alloys. The microstructure of the as-cast K492M alloy mainly consists of γ matrix phase, γ" precipitated phase, MC carbides and (γ+γ") eutectic phase. After heat treatment, the (γ+γ") eutectic phase is nearly eliminated, accompanied by the precipitation of M??C? carbides. The addition of Zr element significantly refines the grain structure of the as-cast and heat-treated K492M alloys. When the Zr content is 160 ppm, the grain structures of both the as-cast and heat-treated alloys exhibit the greatest refinement. With the increase of Zr content from 60 ppm to 580 ppm, the MC carbides in both the as-cast and heat-treated alloys tend to be refined, while Zr element addition has a minor effect on the volume fraction and size of γ" phase. The variation of Zr content has little effect on the tensile properties at room temperature and the tensile strength at high temperature (760 ℃) of the heat-treated alloys, but significantly influences the ductility at 760 ℃ and stress rupture life at 760 ℃/662 MPa. The alloy with 160 ppm Zr demonstrated the highest high-temperature elongation and the stress rupture life, which were 53.8% and 16.8% higher, respectively, compared to the alloy containing 0 ppm Zr.