Iron boron based powders sprayed by high velocity spray processes

Abstract

In this work, a comparative evaluation has been carried out on the deposition efficiency of iron boride powder with a composition of Fe–17.9B–0.4C–1.6Si–0.3Al (wt.%) mixed with Ni powder (20 wt.%Ni) sprayed onto low carbon steel substrate by cold gas dynamic spray processes and the High Velocity Oxy-Fuel (HVOF) spraying method. The particle deformation and bonding mechanism were evaluated. Direct spraying of iron boride powders by low and high pressure cold gas spraying led to depositing a very thin single layer on the substrate, due to the intrinsic brittleness of the powder. Prior to spraying, reducing the particle size (−20μm) and increasing the internal energy of the powders by the ball milling process resulted in no appreciable improvement in deposition efficiency, implying that sprayed particles still had insufficient ductility to plastically deform and flow. Likewise, iron boride powders were spray dried and sintered with Ni particles (FeB-20wt.% Ni) to deposit layers in both low pressure and high pressure cold gas spray processes with various spray parameters. It was discovered that iron boride particles, surrounded by ductile Ni, experienced disintegration and cracking during deposition. The build up of iron boride layers was successfully obtained when spraying FeB20Ni powder by the HVOF deposition method. An abrasion wear test result of the HVOF coatings, 952 HV, was compared with HVOF sprayed WC-12Co coatings.