Preparation And Properties Of Wear-resistant Self-lubricating Composite Coating On Steel Collar Surface

The textile ring is one of the key consumption parts and used frequently in the ring spinning machine,but the use performance of domestic steel collar is not good and the life span is not long.In this paper,the wear resistance of steel collar is improved by the surface treatment of chemical composite plating.The optimized process parameters of electroless plating bath were obtained by single factor experiment,NiSO4·6H2O of the main salt 25g/L,NaH2PO2·H2O of the reducer 30g/L,temperature87 ± 2?,pH4.6.By two orthogonal experiments,the two kinds of nano-Al2O3 and graphite needed for chemical composite plating were added to 6g/L and 2g/L,respectively.According to the optimized electroless plating process,Ni-P-Al2O3 wear-resistant composite coating,Ni-P-Gr self-lubricating composite coating and Ni-P-Al2O3-Gr composite coating with nano-Al2O3 enhanced,Gr antifriction of high wear resistance and low friction coefficient on the 20#steel surface were successfully prepared.The microstructure,surface morphology,microhardness,wear resistance and also formation mechanism of the test samples were systemactic studied by Micro-hardness tester,Optical Microscope,Scanning Electron Microscope,X-ray diffraction and MG-2000 type friction-wear tester.The Ni-P coating,Ni-P-Al2O3 composite coating,Ni-P-Gr composite coating and Ni-P-Al2O3-Gr composite coating prepared by experiment are all amorphous structure in the state of plating.Under the plating condition,the hardness of the four coatings is 507HV,724HV,380HV,470HV,respectively.After heat treatment,the plating began to crystallize,and the coating structures were transformed into amorphous nickel phosphorus alloy intermetallic compound Ni3P at 400?,because the Ni3P particles are fine and dispersed,the dislocation motion is greatly resisted,and Ni3P plays the role of dispersion precipitation strengthening,and the hardness of the four composite coatings reach the maximum,Ni-P-Al2O3(1250HV),Ni-P(946HV),Ni-P-Al2O3-Gr(840HV),Ni-P-Gr(600HV).When the temperature continues to rise,the hardness of the coating begins to decrease,so 400 ? is chosen for heat treatment for one hour.After heat treatment at 400? for 1h.the wear amount of the Ni-P-Al2O3-Gr composite coating is 1.7mg and the friction coefficient is 0.13,which shows good comprehensive wear resistance.In the Ni-P-Al2O3-Gr composite coating,as a kind of hard particle,nano-Al2O3 particles and nickle-phosphours coating form a complex phase through composite deposition.The hard particles greatly enhance the property of the coating hardness and wear-resistance.The Gr particles have nice property of self-lubricating,when they were rubbed.they enabled to form a spreading layer by the lamellar delamination in the coating Gr,so the uniform thickness anti-resistance layer was formed on the samples surface to reduce the friction coefficient and wear losses.The co-action of both particles enabled the Ni-P-Al2O3-Gr coating with properties of high wear resistance and self-lubricating.