Enhancement on mechanical properties of CoCrNi medium entropy alloy via cold spray additive manufacturing associated with sintering

Abstract

Equimolar CoCrNi medium entropy alloy (MEA) has a broad potential for industrial applications due to its excellent strength-ductility synergy. In this study, the emerging solid-state cold spray additive manufacturing (CSAM) approach was applied to fabricate bulk CoCrNi MEA deposits for the first time. However, due to its nature, CSAM normally results in limited metallurgical bonding and weak interfacial bonding between deformed particles, particularly for high-strength alloys such as the CoCrNi MEA used in this work. Therefore, a post-sintering treatment with temperatures ranging from 1200 °C to 1350 °C was applied after CSAM to improve the interparticle bonding and strengthen the as-fabricated MEA deposits. During the sintering process, recovery, recrystallization, sintering necks and grain migration for polycrystalline growth were observed at different stages. The sintering treatment significantly enhanced the tensile strength and ductility of the as-fabricated sample from ∼240 MPa and ∼2 % to ∼660 MPa and 43 %. This study validates the potential of the united CSAM-sintering strategy in additive manufacturing of CoCrNi MEA.