Cryogenic characterisation of selective laser melted cobalt chromium

Abstract

Superconducting electric motors require many small, geometrically complex parts, and manufacturing these can be difficult. Additive manufacturing has various advantages that are beneficial to producing small and intricate structures. However, superconducting electric motors operate under cryogenic conditions, and there is limited information to how laser melted metals, in particular, cobalt chromium, perform under these conditions. This paper explores the change in the mechanical properties of laser melted cobalt chromium under cryogenic conditions. An experimental analysis was conducted at two conditions: room temperature (295 K) and cryogenic temperatures (77 K). The results from these experiments show that at cryogenic conditions, the ultimate tensile strength (UTS) increases to 1201.77 MPa from 780.57 MPa at room temperature. In addition, a study on the effects of heat treatment (HT) to the cobalt chromium specimens after manufacturing was conducted and found to be indeterminably effective. At room temperature, the UTS of cobalt chromium increased by 13% after heat treatment, however, at cryogenic conditions, the UTS decreased by 8% after heat treatment.