Ni-based single crystal superalloy

Abstract

The object of the present invention is to provide an Ni-based single crystal super alloy capable of improving strength by preventing precipitation of a TCP phase at high temperatures. This object is achieved by an Ni-based single crystal super alloy having a composition comprising 5.0-7.0 wt % of Al, 4.0-10.0 wt % of Ta, 1.1-4.5 wt % of Mo, 4.0-10.0 wt % of W, 3.1-8.0 wt % of Re, 0-0.50 wt % of Hf, 2.0-5.0 wt % of Cr, 0-9.9 wt % of Co and 4.1-14.0 wt % of Ru in terms of its weight ratio, with the remainder consisting of Ni and unavoidable impurities.

Description

TECHNICAL FIELD [0001] The present invention relates to a Ni-based single crystal super alloy, and more particularly, to a technology employed for improving the creep characteristics of Ni-based single crystal super alloy. BACKGROUND ART [0002] An example of the typical composition of Ni-based single crystal super alloy developed for use as a material for moving and stationary blades subject to high temperatures such as those in aircraft and gas turbines is shown in Table 1. TABLE 1AlloyElements (wt %)nameAlTiTaNbMoWReCZrHfCrCoRuNiCMSX-26.01.06.0—1.08.0————8.05.0—RemCMSX-45.61.06.5—0.66.03.0———6.59.0—RemRenéN66.0—7.00.31.06.05.0——0.24.013.0—RemCMSX-10K5.70.38.40.10.45.56.3——0.032.33.3—Rem3B5.70.58.0——5.56.00.05—0.155.012.53.0Rem[0003] In the above-mentioned Ni-based single crystal super alloys, after performing solution treatment at a prescribed temperature, aging treatment is performed to obtain an Ni-based single crystal super alloy. This alloy is referred to as a so-called preci...

AI Technical Summary

Benefits of technology

[0013] According to the above Ni-based single crystal super alloy, precipitation of the TCP phase, which causes a decrease in creep strength, during use at high temperatures is inhibited by the addition of Ru. In addition, by setting the composite ratios of other composite elements within their optimum ranges, the lattice constant of the matrix (γ phase) and the lattice constant of the precipitation phase (γ′ phase) can be made to have optimum values. Consequently, strength at high temperatures can be enhanced. Furthermore, since the composition of Ru is 4.1-14.0 wt %, precipitation of the TCP phase, which causes a decrease in creep strength, during use at high temperatures, is inhibited.

[0034] According to this Ni-based single crystal super alloy, the relationship between a1 and a2 is such that a2≦0.999a1 when the lattice constant of the matrix is taken to be a1 and the lattice constant of the precipitation phase is taken to be a2, and since the lattice constant a2 of the precipitation phase is −0.1% or less of the lattice constant a1 of the matrix, the precipitation phase that precipitates in the matrix precipitates so as to extend continuously in the direction perpendicular to the direction of the load. As a result, strength at high temperatures can be enhanced without dislocation defects moving within the alloy structure under stress.

Problems solved by technology

Although the above-mentioned CMSX-2, which is a first-generation alloy, and CMSX-4, which is a second-generation alloy, have comparable creep strength at low temperatures, since a large amount of the eutectic γ′ phase remains following high-temperature solution treatment, their creep strength is inferior to third-generation alloys.

In addition, although the third-generation alloys of RenéN6 and CMSX-10 are alloys designed to have improved creep strength at high temperatures in comparison with second-generation alloys, since the composite ratio of Re (5 wt % or more) exceeds the amount of Re that dissolves into the matrix (γ phase), the excess Re compounds with other elements and as a result, a so-called TCP (topologically close packed) phase precipitates at high temperatures causing the problem of decreased creep strength.

However, since the lattice constant of each phase fluctuates greatly fluctuated according to the composite ratios of the composite elements of the alloy, it is difficult to make fine adjustments in the lattice constant and as a result, there is the problem of considerable difficulty in improving creep strength.

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