Research On Gas Oxygen-Nitrocarburizing Compound Processing And Structure And Properties Of Layer

Study of QPQ salt bath technology research at home and abroad for more than 40 years of history,the technology is mature and widely used.However,emission and waste were generated during the processing, which will be a danger to human health and surroundings and limit its development. We need to develop a new type of surface treatment technology to solve the pollution problem of QPQ salt bath technology.Gas oxygen-nitrocarburizing compound processing as a new surface modification technology has good development prospects,less polluting to the environment during processing.Gas oxygen-nitrocarburizing compound processing is gas nitrocarburizing and post-oxidation of composite process. Artifacts for gas nitrocarburizing and post-oxidation treatment, in high hardness nitrocarburizing layer formed of a oxide(Fe3O4) thin layer,has low friction coefficient and high chemical stability,improving the electrochemical properties on the surface of nitrocarburizing pieces. Gas oxygen-nitrocarburizing compound processing can obviously improve the corrosion resistance performance and wear resistance performance of nitrocarburizing layer,which were widely used in engineering mechanical & medical appliance & car industrial,and other fields.This project studied gas oxygen-nitrocarburizing compound processing technology,developed a highly efficient & environmentally-friendly pro-oxidant. Artifacts obtain high comprehensive performance of post-oxidation treatment. Studied the gas oxygen-nitrocarburizing compound processing, this paper discusses the different oxidation time and oxidation temperature of gas oxygen-nitrocarburizing compound processing create the influence of organization and strengthening layer distribution. Through appearance observation & metallographic analysis and microhardness tests, sample appearance of gas oxygen-nitrocarburizing compound processing was gray black.Gas oxygen-nitrocarburizing compound layer consist of the oxidation layer & the compound layer and diffusion layer.The oxide layer is black in the metallographic microscope,it is difficult to distinguish.Metallographic and appearance by the picture color can be concluded that with the increase of oxidation temperature,oxidation layer thickness increases gradually.Through gas nitrocarburizing processing40 cr steel white layer thickness 6 ? m~ 10 ? m,and gas nitrocarburizing processing H13 steel white layer thickness 10 ? m~ 12 ? m.White layer thickness alter to thin along withthe increase of oxidation time and oxidation temperature.With the increase of oxidation temperature,the thickness of the diffusion layer increases,and oxidation time has little effect on the depth of diffusion layer. Gas nitrocarburizing processing of 40 cr steel diffusion layer significantly thicker than gas nitrocarburizing processing of H13 steel diffusion layer.Surface hardness changes between 500 HV to 600 HV,about 3 ~ 4 times of matrix hardness.On the cross section gas oxygen-nitrocarburizing compound layer hardness performance shows the gradient change.From the table to the substrate,the hardness first increases and then a hardness gradient change trend in smooth transition. The strengthening way was phase transformation strengthening and solid solution strengthening work together.The corrosion resistance performance of gas oxygen-nitrocarburizing compound layer had been studied in this subject and samples were measured by tafel polarization curve & soak test and salt spray test.Determination of tafel polarization curve found gas oxygen-nitrocarburizing compound processing of 40 cr steel and H13 steel corrosion potential higher than gas nitrocarburizing.Along with the increase of oxidation time and the increase of oxidation temperature,the corrosion potential render first increases then decreases,and the oxidation temperature of 450 ? for 1 h the specimen has minimum corrosion tendency. Along with the increase of oxidation time, gas oxygen-nitrocarburizing compound layer soaking test of 40 cr and H13 steel corrosion rate first reduced then increases,and the extension of oxidation temperature corrosion rate increases gradually.The oxidation temperature of 400 ? for 1 h the specimen has the lowest corrosion rate.Along with the increase of oxidation time salt spray test results show that sample appear rusty time first increases then decreases,and along with the increase of oxidation temperature salt spray test results show that sample appear rusty time gradually shorten. The oxidation temperature of 400 ? for 1 h the specimen appeared rusty the longest 18 h of salt spray,and corrosion resistance equivalent to QPQ salt bath treatment. In addition, the development of gas oxygen-nitrocarburizing compound processing technology had obtained production application.This technology was applied in the production of products manufacturing enterprises and produce certain economic benefits.