Powder Bed Fusion Laser Beam (PBF-LB) Of GRCop42. Processability And Influence Of Post-build Heat Treatments On The Microstructure And Thermal And Mechanical Properties

GRCop42 is a precipitation strengthened copper alloy with composition Cu-4at%Cr-2at%Nb developed for high temperature applications requiring high thermal transfer, like rocket engines. GRCop powder with chemical composition within specifications and homogeneous distribution of the alloying elements was obtained by gas atomization at Ceit. GRCop42 parts were fabricated by powder bed fusion laser beam (PBF-LB) and subjected to different heat treatments to achieve the best trade-off between high thermal conductivity and high strength. The microstructure of the as built and heat-treated materials were characterized by SEM and TEM. Dense samples free of defects like pores or coarse Nb-rich islands were obtained in the as-built condition. Subsequent ageing heat treatments at temperatures ranging from 400 to 600 °C precipitated ultra fine Cr2Nb particles, responsible for a significant hardness increase, from 164 up to 260 HV. The effectiveness of the ageing heat treatments in achieving complete precipitation of Cr and Nb from the Cu matrix was evaluated through X-ray diffraction and thermal conductivity measurements.