Effect of heat treatments on the wear resistance of HVAF and HVOF sprayed tool steel coatings

Iron-based coatings are an attractive solution for many wear applications, considering sustainability requirements such as avoidance of critical raw materials and toxic substances. Cold worked tool steels are one potential, yet very undiscovered, material option for coating applications. As a bulk, their careful heat treatment typically produces a martensitic carbide microstructure with very good wear resistance. Compared to bulk materials, the thermal history of a thermally sprayed coating in the as sprayed state is quite different as the microstructure of the sprayed coating does not form in equilibrium. This study explored the potential of AISI D2 cold worked tool steel as a thermal spray coating under different wear conditions. The study investigated different heat treatments to achieve different microstructures of the powder and coatings and their effect on the wear and cavitation erosion properties of the HVOF and HVAF sprayed thermally sprayed tool steel coating. It is important to understand whether the properties of thermally sprayed coatings, which initially have a high defect density, can be improved by heat treatments, and how modification of the phase structures of iron-based coatings affects their properties, in order to extend the use of these coatings.