Plasma rare earth nitriding of nanocrystallized surface layer of 3J33B steel at 350 and 410℃ for different time was studied. The microstructure observation and X-ray diffraction（XRD） analysis show that the nitrid...Plasma rare earth nitriding of nanocrystallized surface layer of 3J33B steel at 350 and 410℃ for different time was studied. The microstructure observation and X-ray diffraction（XRD） analysis show that the nitriding layer consists of compound layer （γ′-Fe4N） and diffusion layer （α-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℃）, 1.75×10 -15 cm2/s （410℃） and 31.313kJ/mol, respectively.展开更多
Plasma nitrocarburizing of nanocrystallized （NC） 3J33 steel were carried out at 400 and 430 ℃ for 4 h in a mixed gas of N2：3H2 and different flow rates of rare earths （RE） La and Ce reagents in this paper. Effec...Plasma nitrocarburizing of nanocrystallized （NC） 3J33 steel were carried out at 400 and 430 ℃ for 4 h in a mixed gas of N2：3H2 and different flow rates of rare earths （RE） La and Ce reagents in this paper. Effects of temperature, rare earth addition and its addition amount on the microstructure and hardness of the nitrocarburized layer of NC 3J33 steel were also investigated. Surface phase composition of the nitrocarburized samples was analyzed by X-ray diffraction. Metallurgical structure, La and Ce concentration and microhardness profiles of cross-sectional nitrocarburized samples were studied using an optical microscope, a scanning electron microscope equipped with an energy dispersive X-ray analyzer and Vickers microhardness tester, respectively. The results showed that the surfaces of the nitrocarburized samples were mainly composed of γ＇-Fe4N and α＇-Fe （α-Fe dissolved with N and C） when the NC 3J33 steel was nitrocarburized at 400 ℃. As the temperature was enhanced up to 430 ℃, the surfaces consisted of γ＇-Fe4N, α＇-Fe and low nitrogen compound FeNx （x=0.0324–0.0989）, and simple substance La was presented when RE flow rate was 0.1 L/min. The addition of La and Ce into nitrocarburized gas increased the thickness and hardness of the nitrocarburized layers. The samples nitrocarburized at 400 ℃ with RE flow rate of 0.025 L/min and 430 ℃ of 0.05 L/min possessed the thickest nitrocarburized layer, highest proportion of nitrides and hardness profile. RE elements could diffuse into the nitrocarburized layer and their concentration increased with temperature. The excess RE impeded the permeation of N, C elements and led to thinner compound layer as well as the diffusion layer.展开更多
文摘Plasma rare earth nitriding of nanocrystallized surface layer of 3J33B steel at 350 and 410℃ for different time was studied. The microstructure observation and X-ray diffraction（XRD） analysis show that the nitriding layer consists of compound layer （γ′-Fe4N） and diffusion layer （α-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℃）, 1.75×10 -15 cm2/s （410℃） and 31.313kJ/mol, respectively.
基金supported by the National Natural Science Foundation of China (50871035 and 51071061)Program of Excellent Team at Harbin In-stitute of Technology
文摘Plasma nitrocarburizing of nanocrystallized （NC） 3J33 steel were carried out at 400 and 430 ℃ for 4 h in a mixed gas of N2：3H2 and different flow rates of rare earths （RE） La and Ce reagents in this paper. Effects of temperature, rare earth addition and its addition amount on the microstructure and hardness of the nitrocarburized layer of NC 3J33 steel were also investigated. Surface phase composition of the nitrocarburized samples was analyzed by X-ray diffraction. Metallurgical structure, La and Ce concentration and microhardness profiles of cross-sectional nitrocarburized samples were studied using an optical microscope, a scanning electron microscope equipped with an energy dispersive X-ray analyzer and Vickers microhardness tester, respectively. The results showed that the surfaces of the nitrocarburized samples were mainly composed of γ＇-Fe4N and α＇-Fe （α-Fe dissolved with N and C） when the NC 3J33 steel was nitrocarburized at 400 ℃. As the temperature was enhanced up to 430 ℃, the surfaces consisted of γ＇-Fe4N, α＇-Fe and low nitrogen compound FeNx （x=0.0324–0.0989）, and simple substance La was presented when RE flow rate was 0.1 L/min. The addition of La and Ce into nitrocarburized gas increased the thickness and hardness of the nitrocarburized layers. The samples nitrocarburized at 400 ℃ with RE flow rate of 0.025 L/min and 430 ℃ of 0.05 L/min possessed the thickest nitrocarburized layer, highest proportion of nitrides and hardness profile. RE elements could diffuse into the nitrocarburized layer and their concentration increased with temperature. The excess RE impeded the permeation of N, C elements and led to thinner compound layer as well as the diffusion layer.
