Study On In-situ Synthesis Of Particle Reinforced Composite Coating By Laser Cladding

Laser cladding creamies particulate reinforced metal matrixe composites(MMCs) on various traditional substrates is an advanced superficial modification technology.Which can enhange the material surface performances,such as resistance to wear,erosion resistance, anti-oxidation and so on.In this technology,in the in-situ synthesis of composite coatings by laser cladding,one or more kinds of ceramics reinforcements with high strength and high elasticitic coefficient are formed by reacting between added elements or compounds under the laser illumination.Because this kind of enhancement body is the thermodynamics steady phase that nucleates and grows from the matrix.The surfaceis pollution-free.Therefore,there inforcements are more compatible with the matrix and the interface bond strength is high.In order to obtain wear-resistant coatings with good properties,the laser cladding of titanium alloys with commercially available KF-Co50 powers and homemade CoTiBSi powers are performed.Microstructure of the cladding coating is characterized using XRD, SEM,and EMPA.The microhardness of the laser cladding coating is measured using HV-1 type miscro-sclerometer.Coatings were examined using an UMT-2 type friction wear tester.In order to get good laser cladding layer on copper alloy surface,through the combination of theoretical calculations of thermodynamics and experiment selected a reasonable coating system.Ni-base alloy composite coating has been produced on Cu alloy surface by CO₂ flow transverse laser. In-situ synthesis ceramic particle reinforced coating.The results of laser cladding with commercially available KF-Co50 powers show that: The coating achieve the better metallurgical combination with the substrate.Its main phase includeTiB₂,TiC,WB and Cr₅Si₃ ceramic phases homogeneously are very thin dispersing in theγ-Co based alloy.The coating phases has dense property and generate dendritic,massive, irregular shape organizations.After analysis the mechanical property of the coating,we find that the hardness of coating is three times higher than the hardness of substrate,which is up to 1000Hv.There is a smooth transition of the hardness from coating to substrate.The wear resistance is obviously enhanced.The main abrasive mechanisms in the coating are abrasive and desquamate caused by the above,which lie in the untreated substrate either,furthermore, adhesive wear appear in the substrate too.The results of laser cladding with homemade CoTiBSi powers show that:In-Situ synthesis of TiB₂ and TiB major ceramic phases dispersing homogeneously are very thin in theγ-Co base alloy.It is evidently different on the microstructure and composition between the dendrites and the intergranular.With the increase of the content of Ti,B in cladding zone the form of reinforcement phase varies with chemical composition of the coating,the small dispersed sheet and massive structure transformed into columnar crystal structure with regularly oriented and uniform distribution.The microhardness of the coating increases prominently comparing to the matrix.And the average value is about three times higher than the titanium alloy substrate.Wear resistance of the composite coating is significant improvement.Ni-base alloy composite coating has been produced on Cu alloy surface by CO₂ flow transverse laser.The results show that the experimental results is basically consistent with the method used Gibbs flee energy function.The system of TiB reinforced particle can be In-situ synthesis.Cladding and the matrix take on free combine interface.The dendrites in the coating dispersing homogeneously are very thin.The microhardness of the coating increases prominently comparing to the matrix and the average value is about three times higher than the copper substrate.