High temperature tribological performance of atmospheric plasma sprayed Cr3C2-NiCr coating on H13 tool steel

Abstract

In hot metal forming, the tool (die) is subjected to complex tribological problems during its interaction with the workpiece and needs more understanding. The reduction in the lifetime of hot forming die by surface degradation is observed as a major problem and adversely affects the process economy. One of the foremost methods of combating wear is the development of wear-resistant surface coatings. However, the study of basic friction behaviour and wear mechanism by which the coatings wear needs more attention. In the current research, the potential of atmospheric plasma-sprayed Cr3C2-NiCr coating on hot forming steel as the wear-resistance coating was explored. The coating was developed on widely used hot forming tool steel namely AISI H13. The microstructure of the coating was found to be dense and uniform with a bond strength of 63.94 ± 4 MPa. The coating hardness and porosity was found to be 830 ± 38 HV and 1.7 ± 0.5% respectively. The friction and wear tests were conducted on a pin-on-disc high-temperature tribometer under two load conditions (25 N and 50 N) and at three temperatures (Room temperature, 400 °C and 800 °C). The specific wear rate was found lower at all testing conditions for the coated surface than uncoated counterparts. The lowest value of specific wear rate and coefficient of friction in the coated specimen was found at the test conducted at 50 N load and temperature of 400 °C. The wear mechanism of worn-out specimens was analyzed using scanning electron microscopy (SEM). The wear mechanism was found more adhesive at room temperature and a combination of adhesive and abrasive at elevated temperature.