Research on W-Mo-Y Multi-elements Co-diffusion treatment and plasma nitriding

Using plasma alloying technique, Q235 steel was firstly treated by W-Mo-Y Multi-elements co-diffusion followed by plasma nitriding process. And then the wear tests were conducted. The effects of technological parameters on alloying layer were studied. The structure, composition, phase and micro-hardness of alloying layer were analyzed by metalloscope, XRD, SEM and microhardness tester. Results show that the microstructure of W-Mo-Y Co-diffusion layer is columnar crystal; W, Mo contents decrease from the outside to the inside. The element Y is distributed mainly at the grain boundaries. The phase of alloying layer consisted of Fe, Fe3Mo, Fe17Y2 and the solid solution of (W, Mo, Y) in alpha-Fe. After plasma nitriding process, the co-diffusion layer is strengthened and large amount of nitrides form and dispersedly distribute in the alloying layer. After nitriding the phase of alloying layer consist of Fe4N, Fe3Mo, Fe, MoN, Mo2N, W2N, WN. the average micro-hardness is 850HV(0.05). Compared with untreated samples, the wear resistance of alloying layer is improved by 2 times under abrasive wear conditions.