Evaluation of mechanical properties of TiB2-TiO2 ceramic composite coating on AISI 1020 mild steel by TIG cladding

Abstract

The main objective of the present work was to enhance the mechanical properties of AISI 1020 steel by depositing the TiB2-TiO2 composite coating on it with the help of the tungsten inert gas (TIG) cladding process. The semi-solid mixture of 50 wt% of TiB2 and 50 wt% of TiO2 was preplaced on AISI 1020 steel and a TIG torch was used as heat source to melt the preplaced layer as well as substrate layer to produce the new coating layer. Characteristics of the cladded layer were examined using Vickers microhardness tester, energy dispersive spectroscopy (EDS), scanning electron microscope (SEM) and x-ray diffractometer (XRD). The TIG currents have shown a significant influence on the microstructure and mechanical properties of the coated layer. Metallography result also shows that the input current of the TIG cladding has considerable effect on the microstructure and quality of the coating. Microstructural changes in the clad layer were studied in detail. The Vickers micro-hardness value of the coated layer increases with decrease in input current and maximum microhardness was achieved about 568 HV0.05 which was about 3.5 times higher than that of the substrate (157 HV0.05). The dry sliding abrasive wear test was performed against EN31 hardened alloy steel as counter body by pin-on-disc tribometer with sliding distance of 1036 meters. The coating produced at lower TIG current (110 A) exhibits minimum average wear rate 1.46 × 10−6 g N−1m−1 while coating processed at higher TIG current (155 A) exhibits higher average wear rate 2.18 × 10−6 g N−1m−1. It was also concluded that the wear rate of the TiB2-TiO2 coating decreases with decreasing processing current and minimum wear rate (1.46 × 10−6 g N−1m−1) obtained up to 2.5 times lower as compare to wear of AISI 1020 mild steel substrate (3.65 × 10−6 g N−1m−1) which makes the TiB2-TiO2 coating suitable for application as wear resistance components. The average coefficient of friction also decreases with increasing TIG current and found maximum (0.76) and minimum (0.58) for the coating deposited at 110 A and 155 A current, respectively.