Microstructure And Properties Of Low Temperature Nitriding Layer And Low Temperature Carburizing Layer Of 316L Austenitic Stainless Steel

In order to improve the surface wear resistance of Austenitic stainless steel,In recent years,Low temperature ion diffusion technique is widely used in surface strengthening of Austenitic stainless steel.This topic was prepared by ion nitriding at low temperature and low temperature ion carburizing samples,and by using optical microscope(OM),scanning electron microscope(SEM),X-ray diffraction(XRD),microhardness,X-ray analyzer,electrochemical devices,such as residual stress of different annealing temperature boronization expansion of sample surface morphology and cross section morphology and group composition,surface residual stress and corrosion resistance testing,the results show that:1.Low temperature ion nitriding has a significant strengthening effect on the surface of Austenitic stainless steel.The service life of the low temperat ure nitriding layer is restricted by the service temperature.The wear resistance and corrosion resistance of the low temperature nitriding layer of the unannealed sample are the best.By 490?annealing 4 h of corrosion resistance,low temperature nitriding layer as the rise of the annealing temperature,abrasion resistance,first sample fall after rise trend.Annealing at different temperature,in the low temperature carburizing specimen without annealing specimens carburized layer at low temperature wear resistance and corrosion resistance of the highest,650?annealing 4h sample corrosion resistance severely reduced.Since the low-temperature diffusion layer is relatively thin,the low-temperature nitriding layer and the low-temperature carburizing layer are damaged to varying degrees under the pressure load of 20N.2.Low temperature nitriding and low temperature carburizing formed expansion austenite phases(N and C)on the surface of the sample.Crystal expansion caused lattice distortion.By measuring the lattice distortion,residual stress on the surface of low temperature nitriding and low temperature carburizing sample was measured.The analysis shows that high temperature annealing can decompose the surface expansion austenite of low temperature nitriding and low temperature carburizing samples and reduce the surface residual stress.3.There is S_C sublayer in the low-temperature nitriding layer,and the supersaturated input of a large number of nitrogen atoms drives the inherent carbon atoms in the matrix to migrate inward,and the S_C sublayer is formed by the concentration in the subsurface layer and reaching the supersaturated state.Due to poor hardness,different levels of polishing"steps"were formed in the metallographic sample preparation process.Under high temperature,the expansion austenite(N and C)in the low-temperature nitriding layer and the low-temperature carburizing layer decomposed.At the same time,part of nitrogen atoms or carbon atoms in the carburizing layer continued to diffuse to the depth of the matrix,resulting in gradual blurring of the boundary between the matrix and the carburizing layer.S _N layer and S_C of nitrogen and carbon atoms will further spread to the depths of the substrate,at high temperature permeability layer desaturation,carbonitriding layer thin,also with the decrease of hardness,bearing capacity to reduce permeability layer,hardness break-down area gradually blurred,no polishing"steps",so in metallographic pictures and SEM images show the S_C and layer gradually widened,and gradually blurred border.