Behavior of Thermally Sprayed Wear Protective Coatings Exposed to DifferentAbrasive Wear Conditions in Comparison to Hard Chromium Platings

摘要

For deposition of protective coatings different coatingtechniques are available. Usually, detailed evaluation ofvarious deposit types and materials is necessary for selectionof the best suited coating for specific application fields anddemands. Subject of this work are thermally sprayedfunctional coatings applied as wear (and corrosion) protectivelayers. Examination of different optimized thermal spraycoatings, I.e. HVOF sprayed WC/Co(Cr) and Cr3C2/NiCrcoatings, conventional flame sprayed and fused self fluxingalloy coatings reinforced by hardmetal and APS sprayed oxideAl2O3/TiO2 and Cr2O3 coatings, is done in comparison to thickhard chromium platings. Two abrasive wear tests featuringwear by lose abrasive particles are carried out. These impartdry wear conditions according to ASTM G65 (Rubber Wheeltest) and wear by abrasive suspensions according to ASTMG75 (Miller test).The work also contains evaluation of newly developed HVOFtorch components permitting increased combustion gas, andtherefore also particle, velocities concerning the benefit interms of coating properties. Exemplary evaluation of the newcomponents influence on velocity and temperature of sprayparticles is carried out by comparative SprayWatch? analyses.Both the influence on the coatings microstructure and the wearperformance are studied. Coating microstructure is evaluatedqualitatively by optical and scanning electron microscopy andthe micro hardness HV0.3 is measured. Worn surfaces arestudied by SEM in order to deduce wear mechanisms.