THE INFLUENCE OF HEAT TREATMENT ON TRIBOLOGICAL AND MECHANICAL PROPERTIES OF HVOF SPRAYED CrC-NiCr COATINGS

The goal of this investigation was to determine the usefulness of CrC-NiCr coatings in order to improve wear resistance of tools made from hot work steels. CrC-NiCr powders were sprayed using the high velocity oxy fuel thermal spray process (HVOF) to form coatings on steel substrates approximately 150 mu m thick. Coatings were heat-treated in a range of temperatures between 900 and 1100 degrees C. The coatings were then evaluated in the as sprayed and heat treated conditions. Inspections by SEM and phase analysis by XRD were carried out. The microindentation technique was applied to measure the variation of the coatings' hardness. Experiments using a tribometer (ball on disc configuration) at room temperature and dry conditions were performed in order to evaluate the friction and wear properties of the coatings. The mechanical properties and wear behaviour of the coatings were correlated with the coating integrity and microstructure.