Development and characterization of cost effective wear and corrosion resistant HVOF sprayed chromite coatings and hard chrome plating

Chromium is an essential constituent for the production of steel against degradation due to corrosion and wear. It is also used in the form of stable chromium oxide precursor in hard chrome plating (HCP). This study is divide into two parts. Firstly, chromite ore (abundantly available in Pakistan) from bulk form was reduced to an average particle size of 50 µm using dry ball milling. The obtained chromite powder was upgraded through gravity separation followed by magnetic separation. Secondly, the upgraded chromite powder was coated on mild steel substrate using High Velocity Oxy Fuel (HVOF) thermal spray system. Another hard chrome plating was made using chromic acid precursor. Structure, morphology, phases and elemental distribution of chromite powder and both coatings were studied using FESEM, XRD and EDS. Particle size distribution of chromite powder was analyzed using sieve analysis. Wear and corrosion rates of HVOF sprayed chromite coatings, HCP and mild steel were investigated. It was found that the wear and corrosion properties of both HVOF sprayed chromite coatings and HCP are superior to mild steel.