Comparison between plasma- and HVOF-sprayedceramic coatings. Part I: microstructure andmechanical properties

Few papers deal with High Velocity Oxygen-Fuel (HVOF)sprayed ceramics. This two-part study thoroughly compares HVOFsprayed Al2O3, nanostructured Al2O3, Cr2O3 to Atmospheric Plasma Sprayed(APS) ones. The first part discusses microstructure and micromechanics.HVOF-sprayed ceramics achieve superior cohesion (lower porosity and lower average pore area). Size effects in Vickers microindentation tests are differentfor HVOF and APS ceramics. At 1N load, hardness is higher for HVOFcoatings (no cracking). Under 5 N and 10 N loads, hardness decreasesgradually for HVOF coatings; APS coatings are largely cracked at 5 N.HVOF-sprayed ceramics are tougher than APS ones and have higher elasticmodulus