Microstructure And Properties Of Al-based Composite Coatings Prepared By Laser Cladding Under High Frequency And Light Vibration

Based on the composition design of AlSiTiNi powder,the bimodal Al-based composite coatings were prepared under the direct laser cladding and high frequency light vibration assisted laser cladding.The macroscopic morphology,microstructure,phase composition,microhardness and wear resistance of laser cladding layer,WC reinforced laser cladding layer and high frequency light vibration assisted laser cladding layer were studied.In addition,these three kinds of coatings were compared and analyzed from the aspects of microstructural change and performance difference.The melting track of AlSiTiNi coating prepared by direct laser cladding present a characteristic which contained lower concave of the middle part and higher convex of the edges.After adding 10%pure Ni powder,the melting channel surface of the coating showed arc shape and the bonding strength of coating and matrix was excellent.The microstructure of 60Al20Si20Ti+10%Ni coating consisted of network structure formed by partially melted regions and petal-like fully melted region.The coating was mainly composed of Al Fe,Fe Ni and Al Cr₂ phases.Under this ratio of the powder,the surfaces of WC reinforced laser cladding layer and high frequency light vibration assisted laser cladding layer were smoother,the cross-section morphology showed arc shape,and the cracks and pores were fewer.In addition,the surface of the coating was corrugated and the lap effect was best when the multi-pass laser cladding test was carried out with 40%overlap ratio under high frequency light vibration.WC reinforced laser cladding layer and high frequency light vibration assisted laser cladding layer have been compared and analyzed.The results showed that the area of the partially melting area in the two coatings decreases obviously,while the area of the fully melting area decreases and the structure of partially melting area is embedded in the solidified structure when the WC content is 20%and the vibration frequency is 551HZ.The bimodal structure was formed by partially melting area and solidified structure,which improved the microstructure and properties of the coatings.The partially melting area plays an important role in strengthening the coating.However,due to the fine grain effect of high frequency micro vibration,the fully melting area is narrowest.The phase constituents for the laser cladding AlSiTiNi coatings are the same as for high frequency light vibration assisted laser cladding AlSiTiNi coatings.The hardness of 60Al20Si20Ti+10%Ni coating was the highest and the average hardness reached the maximum value near 699.6 HV_0.2under direct laser cladding.Moreover,the friction coefficient of the coating was low and the amount of wear loss was the least.On the basis of the coating composition,WC reinforced Al-base alloy coating was prepared.At the same time,60Al20Si20Ti+10%Ni coating was fabricated by laser cladding assisted high frequency light vibration.When the WC content was 20%and the vibration frequency was 551 HZ,the microhardness of the coatings reached 960.5 HV_0.2and 725.2 HV_0.2,respectively.By comparing with the laser cladding AlSiTiNi coating,laser cladding AlSiTiNi-WC coating and high frequency light vibration assisted laser cladding AlSiTiNi coating,the results showed that high frequency light vibration can reduce the fluctuation of the hardness distribution.When the vibration frequency is 551HZ,the running time of the coatings prepared by laser cladding with high-frequency micro vibration was shorter than that of the other two coatings,and the time of stable wear period was prolonged.In addition,the friction coefficient was stable and the fluctuation was small during the stable wear period.The wear morphology of the coatings was better and the amount of wear loss was lower than that of the other two coatings.