Properties of the Ir85Nb15 two-phase refractory superalloys with nickel additions

Abstract

The effects of nickel content on the properties of the polycrystalline Ir 85 Nb 15 refractory superalloy were studied. To examine the possibility of replacing Ir with Ni in Ir 85-X Nb 15 Ni X , we varied the nickel content from 0 to 50 at. pct. The yield strength of the Ir 75 Nb 15 Ni 10 alloy was 2150 MPa at room temperature, much greater than that of the binary Ir 85 Nb 15 alloy, and 728 MPa at 1473 K, similar to that of the binary alloy. The fracture mode of an Ir 85-X Nb 15 Ni X alloy changed from predominantly intergranular in fcc and L1 2 two-phase Ir 85 Nb 15 to transgranular in the two-phase Ir 75 Nb 15 Ni 10 alloy and a mixture of intergranular and transgranular in the other tested alloys when the Ni content exceeded 20 pct. The Ni addition also increased the compression ductility for Ni content up to 50 at. pct. The maximum compression ductility was approximately 13 pct, obtained from Ir 65 Nb 15 Ni 20 . Ir 85-X Nb 15 Ni X two-phase refractory superalloys with X Յ 10 were superior to the binary Ir 85 Nb 15 alloy as an ultrahigh-temperature structural material in terms of strength, fracture behavior, and density.

Compressive creep properties of Ir-base refractory superalloys

“…According to the thermal section of the Ir-Nb-Zr, at the heat-treatment temperature, 1773 K, the volume fractions of the L1 2 phase were from 57 pct in the Ir-13Nb-3Zr alloy to 50 pct in the Ir-4Nb- [18] Fig. 8-Isothermal section of the Ir-Nb-Ni at 1573 K. [17] 9Zr alloy. At the creep testing temperature, 2073 K, the volume fractions of the L1 2 phase were from 58 pct in the Ir-13Nb-3Zr alloy to 47 pct in the Ir-4Nb-9Zr alloy.…”

“…Then, for reference, an isothermal section of Ir-Nb-Ni is shown in Figure 8. [17] A wide fcc and L1 2 two-phase region was observed in the Ir-Nb-Zr system (Figure 1), [11] while the fcc and L1 2 two-phase region was limited in the Ir-Nb-Ni system because of a small amount of solubility of Ni to L1 2 -Ir 3 Nb (Figure 8). The solid circles represent the tested alloys.…”

“…Contact e-mail: mitara.yoko@nims.go.jpThis article is based on a presentation made in the symposium entitled "Beyond Nickel-Base Superalloys," which took place March[14][15][16][17][18] 2004, at the TMS Spring meeting in Charlotte, NC, under the auspices of the SMD-Corrosion and Environmental Effects Committee, the SMD-High Temperature Alloys Committee, the SMD-Mechanical Behavior of Materials Committee, and the SMD-Refractory Metals Committee.…”

Partial phase relationships in Ir-Nb-Ni-Al and Ir-Nb-Pt-Al quaternary systems and mechanical properties of their alloys

“…The fracture strain of the samples showed higher values (around 20 pct) [9] than those of Ir-base binary (lower than 10 pct) [5] and ternary (about 11 pct) alloys. [6] Figure 3 gives the Ni ϩ Al content dependence of the compressive 0.2 pct flow stress at 1200 °C as well as the compressive ductility. On the Nirich region, the strength was over 100 MPa, 3 times that of the Ni-Al binary alloy and more than 2 times that of the commercial Ni-base superalloy, MarM247.…”

“…The investigation on Ir-base binary and ternary alloys showed promising results, such as fcc/L1 2 two-phase structure formation and higher high-temperature strength. [3][4][5][6][7] However, the ductility of these alloys was not satisfactory, as they usually presented an intergranular fracture.…”