Investigation of the feedstock deposition behavior in a cold sprayed 316L/Fe composite coating

Mixing powders in cold spray is a straightforward method to produce composite coatings, but a direct interpretation of the mixed powder deposition behavior from coating microstructure is often difficult. In this study, to investigate the feedstock deposition behavior in a cold sprayed 316L-10 wt% Fe (10Fe) metal-metal composite coating, splats deposited onto the as-polished 316L and Fe coatings with four types of impact scenarios were studied: (i) 316L on 316L, (ii) 316L on Fe, (iii) Fe on 316L, and (iv) Fe on Fe. The splat flattening ratio and coating crater depth/diameter were measured using a light optical microscope (LOM) and an optical profilometer to evaluate the degrees of particle and coating deformation. Finite element (FE) simulations were performed to obtain the splat rebound behavior during impact. A modified ball bond shear test was performed to determine the adhesion strength/energy of the cold spray splats. Results reveal distinct interparticle bonding features in the 10Fe coating, especially at the mixed 316L/Fe interfaces where a preferential location of inter-lamellar cracks can be seen. Similar bonding features were also observed in the deposited splats, indicating the splat on coating tests to be indicative of the coating build-up process. Finally, the feedstock deposition behavior in the 10Fe coating was explained through splat characterizations and FE simulations from hardness, surface oxide layer and particle morphology.Peer reviewed: YesNRC publication: Ye