Preparation Of Ni60-WC/Cr12MoV Bimetallic Composites

In this paper, we further researched the influence of sintering pressure, sintering temperature and holding time on Ni60-WC/Crl2MoV bimetallic composite materials’(BCMs) microstructures and properties, besides, optimized Ni60-WC/Crl2MoV BCMs sintering process according to previous studies, and prepared Ni60-WC/Crl2MoV BCMs suceesfuly. In addition, we studied the effects of heat treatment upon Ni60-WC/Crl2MoV BCMs’ microstructures and properties. At last, formulated preparation and manufacturing processes of Ni60-WC/Crl2MoV bimetallic composite punch preliminary. The results show that:(1) With the increase of sintering temperature, hardness of Ni60-WCwas increased at the beginning and then decreased, and reached the maximum value65.2HRC when the sintering temperature was1120℃, but porosity of Ni60-WC reduced gradually. With the extension of the holding time, Hardness of Ni60-WC was increased at the beginning and then decreased, and reached its maximum value65.2HRC when the holding time was20min. The sintering pressure was benefit to improve Ni60-WC density. The optimum sintering process of Ni60-WC/Crl2MoV BCMs is that sintered at1120℃for20min loading3000Pa pressure followed by furnace cooling to400℃and air cooling to ambient temperature.(2) Under the condition of best sintering process, Ni60-WC/Crl2MoV BCMs were composed of Ni60-WC, transition zone, and Crl2MoV, respectively. The microstructure of Ni60-WC matrix was Ni-Fe solid solution, in which WC particles and multi-eutectic were distributed. The density of Ni60-WC was9.133g/cm3, radial shrinkage ratio was8.0precent, the average micro-hardness of Ni60-WC was measured to be of756HV. There was no microcrack in the Ni60-WC/Crl2MoV BCMs binding interface, Fe、Ni and W atoms diffused in transition layer which is～580μm, and the connection mode belonged to metallurgical bonding. Micro-hardness in transition zone reduced from760HV to316HV gradually. Organization of Crl2MoV was the normalized organization. The average micro-hardness of Crl2MoV was303HV. The tensile strength of the BCMs was191MPa, tensile fracture can be ascribed to brittle fracture in macro and cleavage fracture in micro, but part has toughness. Compressive strength is1627MPa.(3) The resultant samples were heat treated by preheating at860℃, quenching at1020℃, and tempering for two times at520℃for2h. The average micro-hardness of Ni60-WC increased to869HV. Micro-hardness of transition zone decreased from861HV to414HV, and the width of the transition zone increased to590μm. Microstructure of Crl2MoV was translated into tempered martensite matrix, carbides, and a small amount of residual austenite, average micro-hardness increased to758HV. Interface binding strength of the BCMs was increased to241MPa, improving26percent compared with sintered samples, compressive strength was increased to2253MPa, improving26percent compared with sintered samples.