Investigation and characterization of Cr3C2-based wear-resistant coatings applied by the cold spray process

The purpose of this study was to explore the potential of the cold spray (CS) process in applying Cr3C2-25wt.%NiCr and Cr3C2-25wt.%Ni coatings on 4140 alloy for wear-resistant applications. This article discusses the improvements in Cr3C2-based coating properties and microstructure through changes in nozzle design, powder characteristics, standoff distance, powder feed rate, and traverse speed that resulted in an improved average Vickers hardness number comparable to some thermal spray processes. Cold spray process optimization of the Cr3C2-based coatings resulted in increased hardness and improved wear characteristics with lower friction coefficients. The improvement in hardness is directly associated with higher particle velocities and increased densities of the Cr3C2-based coatings deposited on 4140 alloy at ambient temperature. Selective coatings were evaluated using x-ray diffraction for phase analysis, optical microscopy (OM), and scanning electron microscopy (SEM) for microstructural evaluation, and ball-on-disk tribology experiments for friction coefficient and wear determination. The presented results strongly suggest that cold spray is a versatile coating technique capable of tailoring the hardness of Cr3C2-based wear-resistant coatings on temperature sensitive substrates.