Microstructure and Mechanical Properties of Additively Manufactured Rene 65

Abstract

Additive manufacturing has enabled the production of highly complex designs that are not producible using traditional manufacturing techniques. While superalloys such as IN718 have been used in these processes for the manufacture of turbine engine structural components, applications requiring higher service temperatures necessitate the development of alloys with increased capability. Rene 65 was developed as a cast and wrought alloy with increased capability relative to wrought IN718, and characteristics of that alloy, including temperature stability and thermal crack-resistance, made Rene 65 an appealing candidate to withstand the extreme temperature gradients that are characteristic of direct metal laser melting (DMLM) additive manufacturing. The as-built DMLM microstructure is very different from as-forged microstructure, and this work will examine the effect of heat treatments both below (sub-) and above (super-) the gamma prime (γ′) solvus on the grain and precipitate structure of AM Rene 65 material. Tensile, fatigue and creep behavior of the alloy in these different heat treatment conditions is reported. Relative to AM IN718, AM Rene 65 shows the desired improvement in temperature capability analogous to that in the cast and wrought versions of the alloys. Differences in the balance of properties are noted between AM Rene 65 and cast and wrought Rene 65, which are attributable to the differences in grain size and precipitate distribution and which may provide benefits for certain applications.