Plasma spraying method of using the surface covered AI203-TiO2 powder investigation of mechanical properties and microtructure of low carbon steel

In this study, Al2O3-TiO2 composite coatings were thermally sprayed on the SAE 1040 steel using atmospheric plasma spray (APS) process of mixed different rates micron?sized TiO2 and micron-sized Al2O3 powders. The effects of TiO2 addition on the microstructure, phase compositions and microhardness of the coatings were investigated by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and microhardness tester. The results show that the Al2O3-TiO2 composite coatings consists of both fully melted regions and partially melted regions, and the fully melted region has a lamellar-like structure. Phase transformation from mainly stable ?-Al2O3 and anatase-TiO2 in the powders to predominant metastable ?-Al2O3, rutile-TiO2 and Al2TiO5 phase in the Al2O3-TiO2 composite coatings was observed. It was identified that the pore content was decreased with increased of the TiO2 powder rate. The microhardness of the coating layers 3-4.5 times higher than substrate material. The average microhardness values of the coatings were changed as 650-850 HV.