Effect of Mo on the Microstructures and Mechanical Properties of the Polycrystalline Superalloy with High W Content

Abstract

The effect of the Mo contents of 1.0 wt.%, 1.5 wt.%, 2.0 wt.%, and 3.0 wt.% on the microstructures and mechanical properties of the polycrystalline superalloy with a high W content was studied. The typical dendrite morphology was observed in the high-W superalloy with different Mo contents, containing γ matrix, γ′ phase, eutectic, and MC carbide. After the heat treatment, the primary MC carbides were decomposed into M6C carbides, while a needle-like topologically close-packed (TCP) phase was formed in the alloy with high Mo content, in contrast to the other three alloys with low Mo content. The Mo addition increased the lattice parameter of the γ and γ′ phases and also changed the lattice misfits of the γ and γ′ phase lattice misfits towards a larger negative. The addition of Mo improved the yield strength at room temperature due to the solid solution strengthening and coherency strengthening. The improvement of the stress rupture lives at 975 °C/225 MPa was due to the combination of the suppressed propagation of the microcracks by the carbides and a more negative misfit. When the Mo content reached 3.0 wt.%, the TCP phases formed and decreased the ultimate tensile strength and the stress rupture lives as a result.

Quality, Microstructure, and Properties of Metal Alloys

“…The work presented in this Special Issue [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] demonstrates the possibilities of further improving the microstructure quality and mechanical properties of metal alloys.…”

“…In another study [5], the effect of the Mo contents of 1.0 wt.%, 1.5 wt.%, 2.0 wt.%, and 3.0 wt.% on the microstructures and mechanical properties of the polycrystalline superalloy with a high W content was studied. The typical dendrite morphology was observed in the high-W superalloy with different Mo contents, containing γ matrix, γ phase, eutectic, and MC carbide.…”

Effect of Cooling Rate on the Microstructure and Mechanical Property of Nickel-Based Superalloy MAR-M247

“…B and C prefer to form compounds to pin grain boundaries [ 10 , 11 , 12 ]. However, the high percentage of refractory elements (Ta + W + Mo) causes elemental segregation during solidification and the formation of the γ/γ′ eutectic in the interdendritic regions [ 13 , 14 ]. Therefore, solid solution and aging treatments are usually applied to further improve mechanical properties [ 15 ].…”