Microstructural Characteristics and Performances of Cr2O3 and Cr2O3-15%TiO2 S-HVOF Coatings Obtained from Water-Based Suspensions

Abstract

Cr2O3-based coatings offer high hardness, excellent sliding wear performance, and corrosion resistance. Therefore, they are widely applied in the paper industry, as well as for pumps and mechanical sealing systems. Compared to the conventional spray processes, the technology of suspension-HVOF spraying (S-HVOF) allows the production of dense, finely structured coatings with smoother surfaces and improved mechanical properties by using submicron-scaled raw materials. This work investigates the microstructure and performances of Cr2O3 and Cr2O3-15%TiO2 coatings obtained by S-HVOF starting from water-based suspensions. For the development of the suspensions with binary composition, two routes were used to produce ready-to-spray suspensions: (a) mixture of two stable suspensions in the desired ratio, and (b) dispersion of an appropriate alloyed material in the solvent. In order to evaluate the potential of suspension spraying over the conventional APS and HVOF processes, the mechanical properties, corrosion, and sliding wear resistances of the S-HVOF coatings were compared with those of the coatings produced from feedstock spray powders. From the experimental results, it was observed that, in most of the cases, the suspension-sprayed coatings showed denser microstructures, enhanced mechanical properties, wear resistance, and superior corrosion performances.