Research On Ni-based WC Composite Guide Roller Through Cast-Infiltration

Guide roller is one of the key equipments in production line of high-speed rod andwire rolling, gripping red steel in high temperature, within which erosion, fracture andoxidation often occur as a result of thermal shock, heat load and water cooling, lowering itsworking life. Although it can be solved by adding alloy elements into the roller, as theguide roller is integrally made from casting alloy, the price is then expected to be high.Moreover the roller will lose its exact guiding function when it’s worn to the extent of2mm, wasting alloys. Therefore, in order to enhance the working life of guide roller, as wellas save precious metal on account of cost, a hard outside and soft inside composite guideroller with ZG45as the matrix and Ni-based WC particles as reinforcement in alloy wasproduced through surface alloying casting-infiltration.Considering service condition and existing problems of guide roller device, takingadvantages of surface alloying of cast-infiltration, two infiltration casting methods, throughinvestment casting-infiltration and EPC infiltration respectively, were proposed to producethe guide roller and simulated in professional finite element software ProCAST. Thesimulated result shows that both processes were feasible in theory.The microstructure and properties of composite guide roller produced through twomethods of casting were studied though physical experiments. Results show that thecomposite layer of the guide roller produced through investment casting-infiltration wasthinner and with shedding. Besides, there is not enough hardness in surface compared tothe matrix. The composite layer of guide roller produced through EPC infiltration wasmetallurgically bonded with the matrix more uniformly and the maximal micro hardness ofcomposite layer could reach628.5HV, which was much higher than that of the matrix.In order to study the effect of WC particles on the microstructure and properties of thecomposite guide roller produced through EPC infiltration, WC particles with differentparticle sizes and volume fractions were added into the alloy coating to determine the bestones. Results show that alloy coating with35%WC particles in volume, when the particlesbecome larger, properties like hardness, wear resistance at high temperature increase whilethe thermal shock resistance and oxidation resistance at high temperature decreases; whenthe sizes of WC particles in alloy coating were limited in the range of250~420μm, as theybecome more, the hardness and wear resistance increase, while the thermal shockresistance and oxidation resistance at high temperature decreases. The best performance ofcomposite layer surface was obtained when the size and volumetric fraction of WCparticles was150~250μm and50%respectively. The research indicates that the quality of surface alloying of the composite guideroller produced through alloying evaporation pattern infiltration casting is good. Thecomposite layer metallurgically bonded with the matrix, shows no signs of casting defect,providing theoretical guidance and experimental basis for the apply of composite guideroller.