Effect of Heat Treatment on Wear Behavior of Chromoly Steel

Abstract

Chromoly steel is a steel widely used in mechanical manufacturing, it finds many applications for oil and gas, aerospace, and automotive industries. In addition, its ductility, its resistance and its relatively low weight, and its malleability constitute one of the characteristics of choice for the manufacturers. In order to improve the use properties of this steel such as resistance to rupture, corrosion, wear and minimize the risks of fragility, heat treatments are considered in this study. Hence, the objective of this experimental work is to study the effect of heat treatment by quenching followed by tempering at different temperatures on the hardness, structural state, and wear resistance of chromoly steel. In addition, an investigation on the evolution of the rate of bearing surface after friction test was carried out. The results show on the structural level that the sample having undergone quenching followed by tempering at 700°C for 15min, presents a microstructure of globular pearlite with the coalescence of the complex carbides of Mo-Cr-Nb, and a hardness of 226HB. However, regarding the tribological behavior, the sample treated at 600°C recorded an improved wear rate of 49% compared to the sample treated at 550°C. For the wear mechanisms, the abrasive wear mechanism is observed for untreated sample, while the adhesive wear mechanism is dominant for the heat-treated samples. In addition, the rate of the lower bearing surface "Sr2" of this same sample was improved by 2.7% compared to that treated at 550°C.