Study On Microstructure And Wear Properties Of Laser Cladding TiC Reinforced 316L Metal-Based Coating

As one of the typical austenitic stainless steels,316 L stainless steel has good plasticity,toughness and corrosion resistance,good comprehensive mechanical properties,excellent manufacturability and weldability,so it is widely used in aerospace,petrochemical and other fields.In some practical applications,the lower surface hardness(≤200 HV)and wear resistance of 316 L stainless steel limit its application range.Therefore,it is particularly important to modify the surface of 316 L stainless steel to improve its surface hardness and wear resistance.Ceramic-reinforced metal-based coatings have both the plasticity and toughness of metals and the wear resistance of ceramics,which can improve the hardness and wear resistance of materials,and are effective measures to improve the reliability and service life of mechanical parts.This study takes 316 L stainless steel commonly used in industry as the research object,and aims to improve the surface hardness and wear resistance.Laser cladding technology is used as the preparation method for strengthening the coating,and titanium carbide(TiC)ceramic material is selected as the hard coating.phase,a TiC ceramicreinforced metal-based coating was designed and prepared on the surface of 316 L stainless steel.The laser cladding process parameters were optimized based on orthogonal experiments,and the effects of TiC introduction method and addition amount,and TiC particle size on the microstructure and wear properties of metal-based coatings were studied.The main research contents are as follows:(1)The effect of process parameters on the quality of the cladding layer in the laser cladding process was studied.Firstly,through the observation of macroscopic morphology,with the increase of laser power,the cladding layer has a good metallurgical bond with the substrate,but too high laser power will lead to the generation of longitudinal cracks.Then the optimal process parameters are determined by range analysis.The optimized laser cladding process parameters are: laser power 1200 W,scanning speed 5 mm/s,spot diameter 6 mm.(2)The effects of different TiC introduction methods and addition amounts on metalbased ceramic coatings were studied.Under the optimal laser cladding process conditions,coatings with different TiC contents were prepared by external method and in-situ synthesis method.The results show that the macroscopic morphology of the metal-based ceramic coating is good,and the main phases are TiC,(Fe,Ni),and α-Fe.The microstructure is compact,and a large number of TiC aggregate particles are produced in the in-situ synthesized TiC coating structure.The microhardness of the coating directly added 50 wt.% TiC increased the most,reaching 393.7 HV.The microhardness of the coating directly added with TiC is higher than that of the TiC coating with the same mass fraction synthesized in situ.The friction coefficient(0.59)and wear loss weight(35 mg)of the metal-based ceramic coating directly added with 50 wt.% TiC are the smallest,and the wear resistance is the best.(3)The effects of different TiC particle sizes on metal-based ceramic coatings were studied.On the basis of the optimal TiC introduction method and addition amount,the influence of micro/nano TiC on the phase,microstructure,microhardness and wear performance of the coating was analyzed.The results show that the uniformly distributed nano-TiC particles in the coating can form particle strengthening and play a role in refining the structure.The average microhardness of the nano-TiC coating is up to 438.5HV,which is about 2.1 times that of the substrate.Under the dry friction and wear test conditions,the friction coefficient of the nano-TiC coating is only 0.58,and the wear loss weight is the lowest 21 mg.The main wear mechanism of the coating is abrasive wear.In summary,the metal-based ceramic coating directly added with 50 wt.% nano-TiC has good cladding quality,fine microstructure,highest microhardness,best wear resistance,and is more conducive to improving the surface properties of the substrate.The preparation of TiC-enhanced metal-based coatings on the surface of 316 L stainless steel by laser cladding technology provides a technical reference for the development of protective coatings with excellent performance.