The Preparation Technology Optimization And Property Study Of 42MnCr52 Nitrocarburizing Solid Lubricant Coating

Ion nitrocarburizing is one of the chemical heat treatment techniques. Compared with the pure ammonia ion nitriding and gas nitrocarburizing, it has advantages of higher surface hardness, thicker total infiltration, shorter processing time, no producing toxic gas HCN and so on. It can effectively improve the effect of carbon steel ion nitriding, promote the alloy steel and cast iron ion nitriding speed, improve the surface hardness of workpieces, intensify hardening depth and shorten production cycle at the same time.42Mn Cr52 material which commonly used in cylinder liner manufacture of engine is the research object of this project. With adjustment of different process parameters, permeability layer with great comprehensive performance(thickness and thermal fatigue resistance and high temperature wear resistance) was prepared through nitrocarburizing processing. Morphology, Composition and phase struct ure of samples were tested by SEM, EDS and XRD; Thickness and chemical element of the permeability layer were tested by microscope, XPS, AES; Bond strength, hardness and stress of permeability layer were tested by micro-hardness, nanoindenter and X-ray stress analyzer. Friction and wear tests in condition of dry-friction and oil lubrication were performed, which analyzed antifriction, wear resistance and scratch resistance properties of the permeability layer quantitatively.This project optimized preparation process of 42 Mn Cr52 nitrocarburising solid lubricant layer, revealed process of the layer forming on surface of matrix and performed thermodynamics analysis of soft nitriding reaction. Results shows that formation reaction of carbon and nitrogen compounds is able to occur spontaneously.Friction and wear tests in condition of dry-friction and oil lubrication shows that friction coefficients of nitrocarburising solid lubricant coating surfaces reduced to varying degrees than these of surface not nitrocarburised in conditions of different frequencies of friction, load, temperature and so on. Particularly at higher load(200 N) or high frequency(50 Hz) or higher temperature(150 ℃), nitrocarburizing solid lubricant coating surface shows even better anti-friction, wear-resistant and anti-scratch performance.