Preparation And Properties Of A Novel WC-Co Thermal Spray Powder HVOF Coating

The WC-Co coatings sprayed by High velocity oxygen fuel?HVOF?owed good wear resistance and corrosion resistance,was used in petroleum chemical industry,metallurgy,printing,aerospace and other industrial fields widely.There were three kinds of methods were used to prepare WC-Co thermal spraying powder in civil commonly: Sintering crushing method,Melting crushing method and Reunion sintering method.The first two both exist some disadvantages,such as powder more edges,poor liquidity,the adhesive strength of coating was low.The latter?s process was long,high energy consumption and production cost.Aqueous solution method could came ture short process,low energy consumption,high efficiency to prepared the uniform composition of WC-Co powder.But,at present,it was usually used to prepared superfine/nano meter WC-Co powder for high performance cemented carbide,and application in the field of thermal spraying is rarely reporte.Therefore,this research used a adopts new type of WC-Co thermal spraying powder prepared by Aqueous solution method as raw material,and WC-Co coating was deposited on 45^# steel substrate by HVOF with this raw material.Using orthogonal test method to optimize the performance of coating,using OM,SEM,EDS,XRD and EBSD detection methods to research the microstructure,phase composition,and mechanical properties of coating,for the preparation of high performance of WC-Co coating to develop a new path.?1?The new type of WC-Co thermal spraying powder prepared by aqueous solution method was indicated to be uniform particle size,porous shell spherical structure,large surface,Co coated WC particles evenly,W-Co-C uniform mixing highly.?2?In the process of HVOF,new WC-12 Co thermal spraying powder did decarburized and decomposed noticeably.Coating was mainly composed of WC?W₂C?W ?Co₂W₄C phase.The decarburization process both direct oxidation decarburization reaction,and the indirect oxidation decarburization reaction,the decarburization mechanism is compound oxidation decarburization mechanism.?3?Because of new WC-Co thermal spraying powder owe large specific surface area and show activite,it would decarburizated and broke out a large number of W₂C phase during HVOF.But this decarburization reaction would be restained due to WC particles were Co evenly coated.?4?The new WC-Co thermal spraying powder porous shell structure on the one hand is advantageous to the flame flow,and powder was heated evenly,improved the density of coating and content uniformity of phase distribution;on the other hand to improve the deposition efficiency of powder,and efficiency reach up to 56%.?5?The metallographic microstructure of the coating present a typical lamellar structure,WC grain appear rounded edges,WC grain was fine and Co was uniform distribution of WC-Co coating.?6?The thermal spraying powder prepared by aqueous solution method is suitable for HVOF to prepare WC-Co coating,and the comprehensive performance of coating is good,the microhardness of coating can achieve 1218 HV0.3/10,the cracking toughness of coating can achieve 4.85 MPa·m^1/2,the wear mass loss of coating was 0.673 mg/min.Cracking along the crystal extend at the weak interface of Co phase.During abrasive wear,abrasion loss was reduced with roughness reducing and microhardness increasing of coating.