Residual Stress Generation in Laser-Assisted Cold Spray Deposition of Oxide Dispersion Strengthened Fe91Ni8Zr1

This paper examines the residual stresses generated by laser-assisted cold spray deposition of an iron-based oxide dispersion strengthened alloy (Fe91Ni8Zr1 at.%) on an AISI 1018 mild steel substrate, as well as studies of the effect of the laser heating on the substrate alone. The in-plane residual stress values were determined by X-ray diffraction-based measurements. In the top section of the layers, established at a raster deposition rate of 25 mm/s and simultaneous surface heating temperatures of 650 and 950 degrees C, stresses were compressive ranging from - 170 to - 440 MPa. For the substrate only study, a larger span of surface temperatures from 350 to 950 degrees C and scan rates of 5 and 25 mm/s were investigated. Here, the stresses in the laser tracks were tensile, of the order of + 400 MPa, with both W''- and M- shaped profiles about the laser centerline. It was found that the stress profile shape was influenced by the Gaussian power distribution across the laser spot diameter which correlated with microstructural changes (martensite formation) in the substrate.