| Due to its excellent corrosion resistance,heat resistance and oxidation resistance,304 stainless steel is widely used in petroleum,chemical,aerospace,medicine and other fields.However,304 stainless steel has low hardness and poor wear resistance,which greatly limits its application in the field of friction.In order to improve the friction properties of 304 stainless steel,it is an economic and effective way to prepare self-lubricating wear-resistant composite coating on the surface of 304 stainless steel by laser cladding technology.At present,few researchers focused on the preparation of self-lubricating and wear-resistant composite coating on 304 stainless steel by laser cladding technology.In this paper,Ni60 powder and Ti3SiC2 powder are used as raw materials,and the reasonable powder ratios of Ni60-5%Ti3SiC2,Ni60-10%Ti3SiC2 and Ni60-15%Ti3SiC2(mass ratio)are designed.The laser cladding experiments on 304 stainless steel surface are carried out with the most appropriate laser cladding process parameters.Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used to characterize the microstructure and morphology of the coatings.The phase composition of the coatings were determined by XRD.The hardness distribution of 304 stainless steel and coatings were measured by Vickers microhardness tester,and the strengthening mechanism was analyzed.The friction and wear tests of 304 stainless steel and coatings were carried out with high temperature friction and wear testing machine,and the friction coefficient was obtained.The wear rates of 304 stainless steel and coatings were measured with wear mark measuring instrument at room temperature,300℃ and 600℃.The wear surface of 304 stainless steel substrate and coatings were analyzed to explore its wear mechanism.Results showed that the Ni60-Ti3SiC2 composite coatings had good metallurgical bonding with 304 stainless steel substrate,without macro cracks and pores.The composite coatings were mainly composed of continuous matrix Cr0.19Fe0.7Ni0.11 solid solution,hard phase Fe2C,Cr7C3 and TiC,lubricating phase Ti3SiC2.The average microhardness of N1,N2 and N3 coatings were 451.14 HV0.5,419.33 HV0.5 and 359.92 HV0.5,respectively,which were significantly higher than that of 304 stainless steel(238.91HV0.5).The tribologiacl results indicated that the friction coefficient and wear rate of Ni60-Ti3SiC2 composite coatings were lower than those of 304 stainless steel at room temperature,300℃ and 600℃,which effectively improves the wear and friction reduction performance of the substrate.At room temperature,the friction coefficients of Ni60-Ti3SiC2 composite coatings were 0.41,0.46 and 0.48,respectively,and the wear rates are 6.37 × 10-5,16.52 × 10-5 and 4.16 × 10-5mm3/(Nm),respectively.When the temperature rises to 300℃,the lubricating phase Ti3SiC2 slightly oxidized,and the friction coefficients and wear rates of composite coatings increased.The friction coefficients are 0.51,0.56 and 0.53,respectively,and the wear rates are 22.69 × 10-5 26.74 × 10-5 and 22.11 × 10-5mm3/(Nm),respectively.When the temperature rises to 600℃,the friction coefficient and wear rate of the composite coatings decreased due to the joint lubrication of the lubricating film and the dense oxide film.The friction coefficient is 0.38,0.43 and 0.41,respectively,and the wear rate is 12.51 × 10-5,7.58 × 10-5 and 7.79 × 10-5mm3/(Nm),respectively. |
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