14 - Cold spray particle deposition for improved wear resistance

Abstract

This chapter discusses hard coating materials applied by the cold spray process with an emphasis on Cr 3 C 2 –25wt.%NiCr and Cr 3 C 2 –25wt.%Ni blended coatings applied on 4140 alloy for wear-resistant applications. Select material properties of various carbides and cold spray deposition processing are also presented. The chapter discusses the improvements in hard, wear-resistant Cr 3 C 2 -based coating properties and microstructure through changes in nozzle design, powder characteristics, stand-off distance, powder feed rate, and traverse speed, which resulted in an improved average Vickers Hardness Number (VHN) and wear resistance comparable with some thermal spray processes. The cold spray process optimization of the Cr 3 C 2 -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 Cr 3 C 2 -based coatings deposited on the 4140 alloy at ambient temperature. Select coating microstructure and properties using optical microscopy, scanning electron microscopy, hardness, and ball-on-disc tribology experiments for friction coefficient and wear determination have been discussed. Results suggest that cold spray is a versatile coating technique capable of tailoring the hardness of Cr 3 C 2 -based wear-resistant coatings on temperature-sensitive substrates.