The investigation of coating of oxide and cabide compound on the surface of aluminium alloy and bronze by using plasma spray process

In this study, several oxide and carbide powders were coated on the aluminum alloy (AA2024-T4) and bronze surface by use of plasma spray process. Obtained coating layers were investigated according to microhardness, microstructural properties, surface roughness, bonding strength and also thermal expansion properties respectively. Different powder mixtures were tested coated on aluminum alloy (AA2024-T4) surface, such as Al2O3, Al2O3+ TiO2, Al + 5% Cu and Al + 5% Cu + B4C. In addition this, ZrO2+Y2O3, ZrO2+Y2O3+Al2O3, Cu + 5% Al, Cu + 5% Al + Cr3C2 powders were coated with different powder rates of aluminum bronze (Cu alloy) surface. In order to determine microstructure and hardness properties of coated layers, the samples were cross-sectioned perpendicular to the coating interface. All coated samples were subjected to bonding strength tests and surface roughness properties using Ra unit. A scanning electron microscope, also X-Ray (EDX) and an optical microscope were employed for the observations of the microstructure. Dilatometer was used for measuring the thermal expansion properties of coated samples. In order to determine surface roughness value (Ra) and quality, the surface roughness profilometer was used in this study. Furthermore, the dilatometer equipment was employed to measure the thermal expansion coefficient of samples after the coating process on the substrate.The group of A samples which were coated by Al2O3 ve Al2O3 + TiO2 on the substrate (AA 2024-T4), was determined lower porosity, lower hardness value, lower surface roughness value, lower thermal expansion coefficient and higher sticker effect (especially with 40% TiO2 samples). The group of B samples which were coated by Al+Cu and Al+Cu+B4C was performed the highest porosity, highest hardness value and also the lowest surface roughness value, thermal expansion coefficient (especially with %20 B4C samples). Moreover the highest sticker effect (about 48,08 MPa) was obtained the samples without B4C addition.The group of C samples which were coated on the substrate of Al bronze with ZrO2 + 8% Y2O3 and ZrO2 + 8% Y2O3 + Al2O3 were obtained the highest porosity, the highest sticker effect and lower surface roughness and thermal expansion coefficient in addition this, highest hardness value was obtained from the samples of 5% Al2O3 content. The group of D samples which were coated by Cu + 5% Al and Cu + 5% Al + Cr3C2 was obtained lower porosity, lower surface roughness value. However, the samples coated by Cu + 5% Al without Cr3C2 addition was obtained the highest hardness value. The thermal expansion coefficient value could not be obtained on the group of D samples. During coating process, the highest sticker strength value was obtained in lower value because of surface oxidation.