Carbon Potential Effect on Microstructural, Mechanical and Wear Behavior of Carbonitriding Steel for Tribological Application

The present paper investigates the Carbon potential effect on microstructural, mechanical and wear behavior of carbonitrided AISI 4130 steel used for tribological application. The AISI 4130 steel with mechanical performances, due to the presence of molybdenum and chromium as strengthening agents, is widely used in several applications such as the pins, crankshaft, chassis and gears. Although untreated AISI 4130 steels perform well in various environments, they are highly susceptible to wear and corrosion. The microstructure properties of carbonitrided steel with various carbon potential C11(0.8–1% C) and C21(1–1.2% C) were investigated employing optical microscope and XRD. The results of microstructure showed the presence of austenite phase, \(\varepsilon (Fe_{2 - 3} CN),\gamma^{\prime} (Fe_4 N)\) , and chromium nitride precipitation. The microhardness of the carbonitriding steel increased as a function of increasing carbon potential to attain a maximum value of about 865 HV0.1 for C21 and 764 HV0.1 for C11 as compared to untreated steel (270 HV0.1). The microhardness value was more than three times than those of the untreated AISI 4130 steels. Moreover, carbon content has a significant influence on the multi-scratch resistance. The use of multi-pass scratching allowed to examine friction coefficient (COF), wear volume and damage mechanism. Carbonitrided layers revealed a low friction coefficient about 0.065 for C21. The wear volume decreases more than fourteen times than the untreated steel. The carbonitriding treatment allow a significative enhancement of the tribological behavior.