Advanced Alloy Design Program and Improvement of Sixth-Generation Ni-Base Single Crystal Superalloy TMS-238

Abstract

This paper describes the advanced alloy design program (AADP) and improvement of a sixth-generation single crystal superalloy, TMS-238, using this AADP. Creep rupture life prediction equations for five different creep conditions, 800 °C/735 MPa, 900 °C/392 MPa, 1000 °C/245 MPa, 1100 °C/137 MPa, and 1150 °C/137 MPa, were obtained with excellent determination coefficients from 0.95 to 0.98. Using the AADP, we successfully developed three alloys, TMS-238mod-A, TMS-238mod-B, and TMS-23mod-C, which have 10–22 °C higher-temperature capabilities than those of the TMS-238 alloy. The AADP successfully predicted that the creep life was maximized when the volume fraction of γ′ phase was approximately 65% at low-temperature and high-stress conditions, such as 900 °C/392 MPa, compared to that of approximately 60% under high-temperature and low-stress conditions, such as 1100 °C/137 MPa. This prediction enables us to precisely optimize the creep property. Moreover, the prediction equation of the weight change after 1100 °C/1 h oxidation was also updated. The determination coefficient of this equation was R2 = 0.90.