Effect of Gas Mixture H2-N2 on Microstructure and Microhardness of Steel 32CDV13 Nitrided by Plasma

Abstract

Nitriding treatments of low alloyed steels can be performed only at relatively low temperatures in order to avoid a decrease of corrosion resistance due to nitride layers formation. These conditions promote the formation of the compound layer and diffusion zone, which shows high hardness and good corrosion resistance. In the present paper, the influence of the gas mixture N2-H2 in plasma nitriding process on the microstructural and mechanical characteristics of 32CDV13 steel samples was evaluated. This nuance is used in manufacturing mechanical pieces that are greatly solicited in fatigue as the transmission gearings on the helicopters’ rotors and the rolling used in aeronautic. Plasma nitriding treatments were performed at temperatures in the range 773 K for 4 h. The modified surface layer of the nitrided samples consists mainly of the γ’ and ε phases, according to metallographic technique analysis, it seems to be essentially a modification of the austenite matrix. High hardness values are observed in the modified layer with a steep decrease to matrix values.