Tribological studies of carbonitrided coatings synthesized on the 300 M steels by double-glow plasma alloying

The carbonitrided coatings were synthesized on the 300 M steel substrates using a new method named double-glow (DG) plasma alloying. The phase composition and microscopic morphology of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). When the substrate is treated at 950 V source voltage and 500 V workpiece voltage for 5 h, the maximum diffusion thickness is about 100 μm, and the corresponding average microhardness is 10.1 Gpa, which is significantly higher than that of substrate. The phase composition of the carbonitrided layer was composed of γ′-Fe₄(C, N), ε-Fe₃(C, N) and a small amount of CrN phases. Moreover, the wear tests showed that the wear resistance of the carbonitrided specimen was remarkably improved as compared with the substrate. (paper)