| Phosphate coating can improve the friction and wear properties and corrosion resistance of the steel, and extending its life. Manganese phosphate coatings were often used in order to reduce wear resistant because of its larger film weight. To improve the friction and wear properties and corrosion resistance of the surface of fastener, manganese phosphate coating can be prepared on the surface.Manganese phosphate coatings were prepared by various phosphate processes on40NiCrMo7, respectively. The microstructure and chemical composition of the manganese phosphate coatings were studied by SEM(with EDS); Film weight was tested by removing the film; In order to analysze the formation mechanism, phase structure was analyzed by X- ray diffraction. Corrosion resistance can be analyzed by cupric sulfate spot test and NaCl dipping test; The Multifunctional material surface performance tester was used to investigate the wear resistance and the effect of different phosphate processes of coatings under oil-lubricated and dry sliding tests on reciprocating friction-wear, and wear failure mechanism was analyzed.Effect of normal load on the friction and wear properties of phosphate coating were also analyzed.The results showed that three important factors affecting phosphate coating microstructure and properties are the concentration of phosphate solution; phosphating treatment time and temperature of phosphate treatment. Topography of phosphate coatings change with the increasing of concentration, phosphate crystal grain size increased significantly. The crystalline morphology and film weight will directly affect their ability to store grease, thereby affecting its friction and wear properties. An appropriate increase in phosphate temperature and phosphating time are conducive to obtaining good quality phosphate coating, but excessive increase leads to too thick, porous, loose crystal grains, and reduce friction and wear properties. Phase structure of phosphate coating are Mn3(PO4)2?3H2Oand(Mn,Fe)5H2(PO4)4?4H2O. Growth process is divided into: ionization,hydrolysis, oxidation-reduction, and crystallization process. Manganese phosphate coating prepared by optimum process have a fine crystalline, during reciprocating friction-wear process, Friction coefficient is lower than other processes, and after immersion oil lubrication,friction coefficient decreases 62.70%, combined with the wear scar morphology analyze, the wear properties superior to other processes. With the increase of the normal load from3 N to10N, the wear surface of phosphate coating become soft due to increasing temperature,leading to the increase of plastic deformation and the decrease of shear bond strength; flaky exfoliation formed wear debris particles, which act as the third phase, and accelerating abrasive wear. Therefore, the friction coefficient sharply rises first and then slowly declines. At the load of 7N, the phosphate coating failed. |
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