Effect of Ruthenium on Microstructure and Stress Rupture Properties of a Single Crystal Nickel-Base Superalloy

Abstract

The effect of Ru on microstructure and stress rupture properties of an advanced Ni base single crystal alloy has been investigated. The experimental results showed that the addition of 4 wt.% Ru had hardly effect on the phase precipitation behavior of as-cast alloy, i. e., the microstructure is composed of and ' phases for both Ru free and Ru containing alloys. However, under the heat treatments of 1305-1315 /16h solutioning and 1140/4h 870 /20h aging, and the thermal exposure under 1100 /1000h, the addition of 4 wt.% Ru restrained the precipitation and growth of TCP phase evidently, and increased the rafting structure tendency of /' phases. The results of stress rupture tests showed that the addition of 4 wt.% Ru in the alloy improved the stress rupture lives significantly for as-cast, as-heat treated and thermal exposed samples. The improvement of the stress rupture properties may be attributed to the restraint of phase precipitation and growth by the proper addition of Ru.