Diffusion of lanthanum in nanocrystallized surface layer during plasma rare earth nitriding of 3J33B steel

Plasma rare earth nitriding of nanocrystallized surface layer of 3J33B steel at 350 and 410 'C for different time was studied. The microstructure observation and X-ray diffraction(XRD) analysis show that the nitriding layer consists of compound layer (y'-Fe₄N) and diffusion layer (a-Fe). Lanthanum content profiles in nanocrystallized surface layer were measured using glow discharge spectometry(GDS). The results show that lanthanum can'diffuse into the surface layer of the steel to a large depth. Based on the experimental results mentioned above, the diffusion coefficients and activation energy of lanthanum in γ phase are calculated to be 1. 03×10^-15 cm²/s (350 °C , 1. 75 × 10^-15 cmVs (410 °C) and 31. 313 kJ/mol, respectively.