Research On The Microstructure Characteristics And Performance Of NiTi-based Intermetallic Compound Coating Synthesized By Laser Melting Deposition

Due to excellent corrosion resistance,NiTi alloys exhibit a wide application prospective in industry.However,low hardness and poor wear resistance limit their application.To overcome these disadvantages,the NiTi-based intermetallic composite coatings were in-situ synthesized by laser melting deposition.The effect of different NiCr and TC4 contents on the microstructure evolution,hardness,corrosion resistance and wear resistance of the as-produced NiTi-based intermetallic composite coatings are investigated.Some main conclusions were obtained as follow:1.The mixtures of NiCr and TC4 powder with different contents are used as cladding materials.The NiTi-based intermetallic composite coatings are produced by laser melting deposition.The composite coatings are mainly composed of NiTi,NiTi2 and Ni3Ti,whose microstructure is characterized by herringbone and coarse dendritic morphologies.2.When the TC4 content is 5 wt.%,the microhardness of the composite coating increases with the increasing of laser scanning speed.Moreover,when the TC4 content is increased from 10wt.%to 20wt.%,the microhardness of the composite coatings is increased from 800HV0.2 to 850HV0.2,which is～2.5 times higher than that of the substrate TC4 alloy.3.When 10 wt.%and 20 wt.%TC4 powders are adopted during laser melting deposition,the electrochemical tests of the as-produced composite coatings are performed in 3.5wt.%NaCl and SBF solutions.The results show that,when the TC4 content is 20 wt.%,the corrosion resistance of the composite coating is highest in NaCl solution.While the TC4 content is 10wt.%,the corrosion resistance of the composite coating is highest in SBF solution.Moreover,when the TC4 content is 5wt.%,the corrosion resistance of the composite coating is relatively lower than that of the substrate TC4 alloy.When the laser scanning speed is 13 mm/s,the corrosion resistance of the composite coating is highest.However,when the laser scanning speed is 11 mm/s,the corrosion resistance of the composite coating is lowest.4.The wear resistance of the composite coatings is increased with the increasing of TC4 contents in the cladding powder.Moreover,when the TC4 content is 5 wt.%,the wear resistance of the composite coating first increases and then decreases with the increasing of laser scanning speed.When the laser scanning speed is increased to 13 mm/s,the wear resistance of the composite coating is highest.