Effects of Isochronal Annealing on Microstructure and Properties of Low Temperature Nitriding Layer of 316L Stainless Steel

The effects of annealing temperature on the microstructure, surface hardness, wear resistance and corrosion resistance of S phase of AISI 316L stainless steel in the low temperature nitriding layer were studied. The samples after low temperature nitriding were annealed at 450 ℃, 470 ℃ and 490 ℃ for 4 h. Comparing with the unannealed low-temperature nitride samples, the testing infiltrated layer section microstructure, the XRD diffraction pattern, the cross-section hardness gradient and the YG6 tungsten carbide steel ball under 10N pressure load were analyzed.The wear morphology was observed by scanning electron microscopy and 3D, and an electrochemical workstation was used to study the corrosion resistance of seepage. The results show that the annealing temperature has a significant effect on the S phase of the low temperature nitriding layer, the precipitation degree of infiltrated layer increases with the increase of annealing temperature, nitrides are precipitated after decomposition of S phase by high temperature annealing, as a result, the matrix is "poor Cr" and the corrosion resistance decreases. Corresponding, with the increase of annealing temperature, low temperature nitriding layer precipitates CrN and Fe_xN_y gradually, the bearing capacity of infiltrated layer decreases and the wear resistance reduces.