Abstract

The Cold Gas-Dynamic Spray Method (CGSM) is a means of producing coatings or free-standing structures from powder feedstocks, on metallic, polymeric or ceramic substrates, through the use of high particle velocities obtained by the control of gas dynamics in converging-diverging nozzles. The method expands the existing temperature-velocity domain of thermal-spray technology by permitting formation of coatings at relatively low temperatures with spray patterns governed largely by the gas dynamics of the nozzle. The coatings are formed by the energetic impact of the feedstock particles, whereby inter-particle bonding appears to be governed by the deformation of the particles accompanied by creation of copious amounts of fresh surface area available for interparticle bonding. Because of the novelty of the process, very little basic information exists regarding the mechanical properties and microstructure of the coatings. This work reports the outcome of investigations aimed at more clearly understanding the mechanical properties and microstructural characteristics of prototypical CGSM coatings formed from commercial copper and steel powders. Techniques include optical, scanning and transmission electron microscopies, microhardness and residual stress measurements. Early results suggest the materials to have significantly different properties than coatings made by more traditional thermal spray or cladding processes.

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