Effect of Process Parameters on Twin Wire Arc Sprayed Steel Coatings

There has been a growing interest in additive manufacturing technologies for the protection and repair of metallic structural components. Among the proposed techniques, the twin wire arc spraying process offers the advantage of high deposition rates coupled with process robustness and versatility. The fundamental materials science of these sprayed coatings is surprisingly still under-explored, and depositions with enhanced mechanical properties should be achievable with this additive technique given its high temperature and rapid quench rates. Motivated by these considerations, we performed a study on the deposition of steel coatings using a twin wire arc spraying system. An array of dense steel coatings was fabricated using compressed air and altering process conditions to include variations in carrier gas pressure, standoff distance, and torch power. Coating structure and morphology were evaluated with scanning electron microscopy, while energy-dispersive x-ray spectroscopy was used to assess elemental composition. Vickers hardness was measured on coating cross sections. Correlations were made between process conditions and coating morphology, microstructure, element content, and hardness. Two distinct lamellae regions of varying oxide content and hardness were observed throughout the coatings. The influence of process conditions on coating density and deposition rate is also discussed.