Effect of process temperature on the microstructure and properties of gas oxynitrocarburized 35CrMo alloy steel

In the present investigation, 35CrMo alloy steel was gas oxynitrocarburized at 550 °С, 570 °С and 610 °С for 2 h by applying a low-temperature gas multi-elements penetrating system. Microstructure, surface composition, case depth, microhardness, wear and corrosion resistance were analyzed. The compound layer consisting of γ′-Fe4N and ε-Fe3N and oxide layer of Fe3O4 and Fe2O3 were formed on the ground reference surface after treated. Compared with the conventional gas nitrocarburizing, a larger effective case depth was obtained successfully in a short time after treatment. The microhardness and the properties of wear and corrosion resistance were improved obviously and the properties of samples treated at 570 °C are optimum when compared with the samples treated at 550 °С and 610 °С for the same duration.