The effect of boron and zirconium on the microstructure and tensile properties of Nimonic 105 superalloy

Abstract

In the present study, the effects of boron and zirconium on the microstructure and high-temperature tensile properties of Nimonic 105 superalloy were evaluated. For this purpose, three alloys with different contents of boron and zirconium (0.003 wt% B-0 wt% Zr, 0.013 wt% B-0 wt% Zr, 0.003 wt% B- 0.16%wt% Zr) were prepared via VIM + ESR process. Optical and scanning electron microscopes, x-ray diffraction analysis and tensile testing at 25 and 700 °C were used to describe the alloys structure and properties. The results showed that the microstructure of the 0.003 wt% B-0 wt% Zr alloy consisted of thin-film (Cr, Mo)23C6 and blocky (Ti, Mo)C phases in the γ matrix. The addition of zirconium changed the type of carbide to MC one while boron improved the formation of discrete M23C6-type carbide. The XRD analysis results revealed an increase in the lattice misfit of the γ/γ´ phase for the B and Zr-added alloy, a decrease in the M23C6/γ misfit for the B-added alloy and the MC/γ phase misfit for the Zr-added alloy. In addition, a significant effect of zirconium on grain size were observed in the alloys. Boron and zirconium decreased the ductility at room temperature by 3% and 6% and increased it at 700 °C by 7% and 13%, respectively. Moreover, boron and zirconium increased the high-temperature yield strength by 9% and 13% and ultimate tensile strength by 9% and 16%, respectively.