Study On The Technology Of Plasma Nitriding And Plasma Nitrocarburising Of Austenitic Stainless Steel In The Low Lemperature

This article firstly describes the background, the content and the meaning and the research and development of the situation around domestic and foreign about plasma nitriding. Then it analysises the basic principles, basic concepts and the superiority of plasma nitriding with other nitrogen methods and plasma nitriding strengthen of the method.The glow pulse plasma nitriding furnace with their own was used in the experiment. The material of the sample is the AISI 304 austenitic stainless steel and the surface was polished and cleaned before treatment, and then the sample was flatted on the cathode in the vacuum chamber during the plasma nitriding.In order to more accurately measure and control the treatment temperature, flexible thermocouple with the end of the insulation was used and contact with the sample surface. Experimental research on the potential of different nitrogen in the low temperature and change distances from the auxiliary cathode in the ion nitriding process with the glow pulsed plasma nitriding furnace; It also research on the carbon content at different ion carbonitriding technology in the low temperature and compare the the characteristics of the NT(nitriding), NT+NTC (nitriding+carbonitriding)and NTC(carbonitriding) technology.The phase component of the modified layers were studied by means of XRD; the surface of morphology of modified layers were examined by SEM and; the hardness of nitrided layers were tested by micro-hardness tester; the cross sections morphology and the thickness of modified layers were measured by metalloscope; the friction coefficient and the wear resistance were measured by wear tester.; the components of N and C in the different depth were tested by glow discharge spectrometry(GDS) and the corrosion resistance of modified layers wear tested by electrochemical.Test results showed that:S phase formed easily at lower nitrogen potential condition but nitride precipitates at higher nitrogen potential for austenitic stainless steel. The result revealed that nitrided layer microhardness and thickness of the nitrided samples are increased regularly as the nitrogen potential increased. The corrosion resistance of modified layers is also better than the unmodified layers; The hardness increased significantly of austenitic stainless steel with the auxiliary cathode. The hardness of nitrogen solution to increase further due to the combined effect has decreased. The microhardness are increased firstly because of nitrogen solution and then decreased because of the combined. Surface roughness values gradually increase. Nitriding of the depth increased significantly, when the distance from the samples to the auxiliary cathode about 5 mm and 10 mm, the thickness of the layer increases obviously;The result revealed that good layersγC andγN are formed in Plasma nitrocarburising at low temperature and the maximum N and C content in the layer are in the different depth.carbon atoms are crowded internal by nitrogen and expand the nitriding depth.The thickness and the hardness of the treatment layer reach to maximum when the C2H2 content is 3% and the thickness and the hardness of the treatment layer are decreased when the C2H2 content is 5% due to the carbon saturated;Austenitic stainless steel NT treatment has higher hardness gradient, but NT+NTC and NTC treatment have more favorable hardness gradient, the load capacity of modified layers are increased. The maximum N and C content in the layer are in the different depth, carbon atoms are crowded internal by nitrogen and expand the nitriding depth.