Study On In-situ TiC Reinforced Composite Coating For Grey Cast Iron By Laser Alloying

The microstructure of grey cast iron is that the flake graphites distributed on the pearlite or ferrite matrix,which makes the grey cast iron has good wear-resistant but low hardness.Laser alloying reinforced ceramic phase metal matrix composites on various substrate is an advanced surface modification technology,utilizing laser alloying technology to modify the surface of grey cast iron could enhance the material surface performance,such as wear resistance,corrosion resistance,improve the usability of grey cast iron and prolong the service life of grey cast iron equipment.In this paper,grey cast iron and Ti powder are selected as the substrate and the alloying material to process in-situ Ti C reinforced coating.Study on the influence of laser alloying processing parameters on morphology and property of coating.For the coatings in different paramenters,its microhardness and wear profermance are tested,development the surface of grey cast iron which is eliminate the harmful phase of impurities,pores and compounds,improve the quality and performance and decrease the damage of graphite relative to the structure and properties of grey cast iron.In this paper,the laser power was 2k W to 3.5k W and the scanning speed was 5mm·s^-1to 20mm·s^-1,used a fiber laser beam to conduct laser alloying coating on the surface of grey cast iron.The constituents and microstructure of the coatings were examinted by VHX-600K digital microscope,SEM and XRD,the friction and wear tester,hardness tester used for the wear resistance and the microhardness distribution investigate of the alloyed coating.Discess the effects of laser power and scanning speed on the shape and quality of the laser molten pool.The study on the geometry of the laser alloying zone shows that the laser process parameters have an important influence of the alloyed coating.At the same scanning speed,the depth and width of the laser melt channel was increase and the thickness of the heat affected zone decreases as the laser power grows in the laser alloying of grey cast iron surface.As the laser scanning speed increases,the depth and width of the laser alloying bath decrease,and the cross-sectional shape of the melt tunnel develops from a semicircle to a semi-ellipse.The effect of laser power on the shape of the molten pool is more pronounced.The increase in laser power and the reduction in laser scanning speed increase the size of the Ti C reinforcing phase in the laser alloyed coating.The microhardness of the laser alloying coating on the grey cast iron surface is affected by the laser process parameters.The microhardness of the coating cross-section is400 HV to 1000 HV,which is 2-4 times that of the substrate.The increase in laser power and the reduction in scanning speed result in an increase in the microhardness of the laser alloyed coating.The friction coefficient of the laser alloying coating is 0.6,the wear amount in the 30min is less than 0.5mg,and the friction performance is excellent.The principle of friction is adhesive wear and abrasive wear.