Reusing 316L Stainless Steel Feedstock Powder for Cold Spray Deposition

Abstract

Cold spray (CS) is a solid-state deposition of coatings, or an additive manufacturing (CSAM) process employed to make parts maintaining the feedstock powders properties in the deposited material. One of the cons for industrial use of CS or CSAM is their higher costs compared to the traditional coating or manufacturing processes. Reducing the feedstock powder consumption by maximizing the deposition efficiency has been the focus of many works. However, depending on the part geometry (e.g., a plate with holes), and CSAM strategy with low deposition efficiency, a considerable mass of powder can pass through the substrate, failing to bond, and becoming a process waste. This work evaluates CS 316L stainless steel coatings, recovering the unbonded particles and reusing them in a later deposition, thus making coatings with reused powders. The original and recovered powders were characterized in terms of particle shape and size distribution, phase composition, microhardness, and other properties to evaluate the evolution of the particles' properties due to the recovery process. Besides the powders, the CS coatings obtained with original and recovered powders were evaluated through cross-section image analysis, where porosity, deposition efficiency, and microhardness were observed. The results indicate that the powders' physical properties undergo variations over multiple deposition cycles without significantly affecting the quality of the CS coatings, with porosity below 1.5% and microhardness around 350 HV_0.3 in most cases. Recovering and reusing powder for CS promotes environmental sustainability and generates significant economic benefits. This study contributes to making CS more economically viable from a life cycle cost assessment perspective.