Enhancing the deposition capability of Cr3C2–NiCr in kinetic spraying via damage accumulation in feedstock powder

Abstract

In previous studies on the kinetic spraying of cermet (e.g., WC-Co and Cr3C2–NiCr) the fragmentation of kinetic sprayed cermet particles was a prerequisite for successful deposition. Therefore, the properties of the feedstock powder related to fragmentation are significantly critical factors. In this study, a commercial Cr3C2–25NiCr powder was mechanically milled to accumulate damage in the feedstock powder and reduce the fragmentation resistance of the cermet particles, then heat-treated to relieve the strain hardening effects on the metal part (NiCr). The effects of the mechanical milling and heat-treatment were evaluated using a nanoindentation test, a powder compression test and transmission electron microscope observation after which the deposition characteristics of three kinds of powders (as-received, milled, and milled + heat-treated) were compared. The Cr3C2–25NiCr powder was considerably weakened by mechanical milling. There was no recovery of the fracture toughness and phase transformation of the milled Cr3C2–25NiCr powder even after the heat-treatment. Consequently, the deposition state of the milled and heat-treated Cr3C2–25NiCr powder was considerably enhanced compared with the as-received powder. Thus, mechanical milling and post heat-treatment of the commercial Cr3C2–25NiCr powder seems to be effective at enhancing its deposition capability for the kinetic spray process.