Thermophysical properties of additively manufactured (AM) GRCop-42 and GRCop-84

Abstract

Additive manufacturing (AM) has enabled new opportunities of high-performance alloys for use in complex components across the aerospace, industrial, automotive, and energy industries. These industries have growing interest in copper alloys and AM for high-performance heat exchangers such as rocket engine combustion chambers. GRCop copper alloys, such as GRCop-84 (Cu-8Cr-4 Nb at%) and GRCop-42 (Cu-4Cr-2 Nb at%), have high thermal conductivity and high mechanical properties at elevated operating temperatures. In this paper, thermophysical properties for GRCop-84 and GRCop-42 produced using laser powder bed fusion (L-PBF) are examined. While L-PBF parameters and resulting microstructures can be achieved in a laboratory environment, those parameters do not always translate well into a production environment, and the variations across multiple machines and powder chemistries must be understood. The repeatability and reproducibility of samples across the commercial supply chain is critical for designers to ensure parts meet operational requirements. Thermophysical properties, such as thermal conductivity and thermal expansion are key design attributes. Thermal conductivities for eight GRCop-42 blocks and two GRCop-84 blocks were measured from room temperature up to 700 ℃. Thermal expansion was also measured from 20 °C to 1000 °C. These GRCop alloy parts were made with gas atomized powders from different vendors and with different L-PBF systems and parameters. Equations for the thermal conductivity and expansion are given. The variation of thermal conductivities for L-PBF GRCop parts is estimated to be less than + /− 4%. Based on phase analysis, compositional analysis, and thermal conductivity measurements, the small variations in thermal conductivities for the L-PBF GRCop parts are elucidated. The thermophysical property variations can be used to establish process capabilities and design guidelines for ongoing commercial use and further research.