Effect of Feedstock Characteristics and Operating Parameters on the Properties of Cr₂O₃ Coatings Prepared by Suspension-HVOF Spraying

Chromium (III)-oxide (Cr₂O₃) is a widely used coating material for applications in the printing, paper and textile industry, pumps and mechanical sealing systems. Cr₂O₃ coatings offer high hardness, excellent sliding wear performance and corrosion resistance. Suspension-HVOF process (S-HVOF) allows the production of dense, finely structured coatings with smooth surfaces and improved mechanical properties. The current work presents a study on the development of ready-to-spray aqueous Cr₂O₃ suspensions starting from different commercial available powders and the effect of suspension characteristics (particle size distribution, viscosity, stability) and operating parameters (gas composition, spray distance) on the microstructure, microhardness and deposition efficiency of the S-HVOF Cr₂O₃ coatings. By appropriate choice of the suspension and spraying parameters, thick (> 100 μm) and mechanical stable (microhardness higher than 1500 HV0.3) suspension sprayed Cr₂O₃ coatings were produced.