Investigation Of Plasma Sprayed Mo/WC-Co Coating On Mould CuNiCoBe Alloy

With the development of sicence and technology, continuous casting and rolling wereused more and more widely in the steel industry. As the core component of continuouscasting, the stability performance of mold directly affected the operation rate and thecontinuous casting bloom quality.So the mold surface properties would be higher. Althoughcopper mold material had been developing, its service time was short without surfacetreatment. In order to increase the service time of CuNiCoBe mold, the plasma sprayingtechnology was used to prepare WC-Co coating, Mo coating and Mo/WC-Co coating onthe surface of mold. The plasma spraying processing parameters were optimized by theuniform test with the bonding strength between the coating and the substrate as an indicator;Particle temperature and velocity were measured by SprayWatch online detectionsystem;The microstructure and phase composition of the coatings were investigated bymeans of SEM, EDS, XRD and so on; The thermal shock test was done to investigate thethermal shock resistance of the coatings;The hardness of the WC-Co coating and Mocoating were tested to analyze their distribution; Ultrasonic impact treatment was made onthe coatings to investigate the influence on the thermal shock property; Friction and wearproperty was tested on the coatings, the results are as follows:The process parameters optimized of Mo coating was: Spray distance115mm, power25.5kW, powder feed rate8g·min-1, main gas flow60L·min-1. Bonding strength of the Mocoatings optimized was58.743MPa; The process parameters optimized of WC-Co coatingwas: Spray distance95mm, power25.5kW, powder feed rate10g·min-1, main gas flow85L·min-1. Bonding strength of the Mo coatings optimized was26.794MPa.The greaterparticle speed was, the higher bonding strength two kinds of coatings got. Mo coatingsfollowed this rules more obviously.A certain degree of pores existed in the coatings, and pores affected coatings`quality;The binding mode between coating and substrate, Mo coating and WC-Co coating was mainlymechanical bond. Mo coating improved the bonding strength obviously, with its roughsurface; Mo was oxidized during spraying process, and new phase MoO3generated;WC-Co was oxidized and nitrided during spraying process, and new phase WO3, WN,CoWO4generated. The oxide dispersed in the coatings increased the hardness of surfaceand wear-resisting property. Mo coating provided buffering effect, and reduced stress concentration, extended thethermal shock time.After ultrasonic impact treatment, the surface roughness of the two kinds of coatingsdecreased, and Mo coatings`decrease was more.Hard particles WC in the coatings blocked the extension of the nick, and improvedwear resistance property of the coating; The micro hardness was scattered, but it obeyed thenormal distribution.