Optimization of Process Parameters in a Laser Fe/Ti3SiC2 Composite Coating and Its Microstructure and Properties
Traditional hard coatings are typically prepared on the surfaces of crankshafts,shingles,and other friction parts to improve wear resistance.However,these coatings have been shown to have no wear-reducing effect on their counterparts,and the overall wear-reducing effect is poor.In this study,Fe/Ti3SiC2 wear-resistant and friction-reducing composite coatings were prepared on the surfaces of specimens of 45 steel using high-speed laser cladding technology under different process parameters.The objective was to achieve a friction vice that improves the wear resistance of the workpiece and reduces the wear of dyadic parts.The hardness of the composite coatings was examined under different process parameters using a Vickers microhardness test.Friction wear tests of the composite coatings under different process parameters were conducted at room temperature using a friction wear machine,and the wear mark morphology was characterized by scanning electron microscopy.Elemental analysis of some specimen areas was performed using self-contained energy dispersive spectroscopy.The wear amount of each coating on the pin of the grinding specimen was recorded as a criterion,and the mean value and extreme deviation of each process parameter were calculated to optimize the process parameters of the high-speed laser melting of the Fe/Ti3SiC2 wear-resistant and friction-reducing composite coatings.X-ray diffraction and optical microscopy were utilized to examine the physical phases and cross-sectional morphology of the composite coatings under different process parameters,and the effects of these process parameters on the organization and properties of the coatings were investigated.The optimal combination of process parameters for the composite coatings was estimated to be a laser power of 2.5 kW,powder feeding amount of 15 g/min,scanning rate of 14 mm/s,and coating microhardness of 591.7 HV0.2.The macroscopic morphology of the cross-section of the single-pass cladding layer of the coating in the laser power was constant.When the scanning rate was too fast or the amount of powder delivery was too large,the dilution rate of the coating decreased whereby the coating showed an morphology,which in turn prevented the coating and substrate from forming a good metallurgical bond.The combination of coating and substrate was mainly composed of columnar,dendritic,and planar crystals,but the size of the organizational structure of the coating changed under different process parameters.With an increase in laser power,the input heat increased and the degree of subcooling decreased such that the grains coarsened.With a suitable increase in the scanning rate and amount of powder delivery,the fusion layer of powder particles was subjected to a lower heat and the rate of subcooling increased,which led to a refinement of the grains.A 30-min friction wear test at room temperature and under a 30-N load showed that the composite coatings under different process parameters exhibited different abrasion patterns.By contrast,the composite coatings under the optimal process parameters showed the best friction performance,where the amounts of wear of the coating and paired parts were 0.4 and 0.7 mg,respectively.Compared with the amount of wear of the matrix of non-fusion-coated composite coatings under the same friction wear test parameters,the wear amount of the composite coating was reduced by 94％,whereas that of the couple was reduced by 65％.By contrast,the Fe-based coating without Ti3SiC2 under the same parameters did not reduce the wear amount on the couple despite an increase in abrasion resistance;the wear amount on the couple was increased due to its own hardness.These results showed that the addition of composite coatings under appropriate process parameters,greatly improving the wear resistance of the workpiece surface while reducing wear on the dual parts.Thus,the performance of the entire friction system was systematically improved under the high-performance wear-resistant friction-reducing composite coatings.This study solves the technical problem wherein traditional hard coatings,despite enhancing the wear resistance of the workpiece,increase the wear of the spouse parts.
high-speed laser claddingcomposite coatingsprocessing parameter optimizationmicrostructurefriction and wear
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