HVOF spraying of Al2O3-dispersion-strengthened NiCr powders

The high-energy ball milling technique is an effective method for producing powders for metal matrix composites. In this study, Al2O3-dispersion-strengthened NiCr spray powders were produced using the high-energy ball milling process. The milled powders were sprayed using a high velocity oxy-fuel (HVOF) spraying process. Both the powders and the coatings were studied in terms of their microstructure and microhardness. The abrasive wear resistance of the coatings was evaluated using pin-on-disk tests. It was found that the starting precursors influenced strongly the properties of the milled powders. Dense coatings with homogenous microstructures could be produced by the HVOF process. The microstructure of the milled powders could be mostly retained in the coatings after spraying. The wear resistance of the coatings depended on the properties of the milled powders. The higher the Al2O3 volume fraction and the more homogenous structure the powder had, the more wear resistant the coating was.