Printing requirements for cemented carbide
Because of its superior properties such as high strength, hardness, excellent wear resistance and oxidation resistance, carbide is widely used in mechanical processing, petroleum mining, mold forming and structural wear-resistant parts and other fields. In the production of cemented carbide, sintering is the most important process. Even if the compacts are the same, different sintering processes have different effects on the properties of the sintered products. For a long time, many researchers have gradually formed a variety of sintering methods in actual production, including vacuum sintering, hot isostatic pressing sintering, vacuum follow-up hot isostatic pressing, sintering, hot isostatic pressing, etc..
Its disadvantages are: there are a small amount of pores and defects in the product, and the carbon content of the sinter will decrease.Hot isostatic pressing sintering in sintering with inert gas, liquid metal or solid particles as pressure transfer medium in each direction of the sintered body exert equal pressure, not even this can overcome ordinary hot pressing pressure is not uniform and the resulting product performance. The hot isostatic pressing of cemented carbide can eliminate the pores in the alloy and the drilling pool after sintering, and restrain the growth of WC grain. The Kennametal Inc installed the first heating chamber for 277mm * 1270mm in 1967. The temperature is up to 1500oC and the pressure can reach140MPa's hot isostatic pressing machine has taken the lead in successfully applying the technology of hot isostatic pressing to the production of cemented carbide. Since then, hot isostatic pressing technology has developed rapidly in foreign countries (especially in the United States).
Since 80s the advent of nano cemented carbide, and gradually formed a new sintering method, such as microwave sintering, field assisted sintering (such as spark plasma sintering and plasma activated sintering), two stage sintering, selective laser sintering etc..Vacuum sintering (Vacuum Sintering) is one of the more widely used methods for cemented carbide sintering, which began in the 30s of last century,Great progress has been made in the past thirty years. Vacuum sintering is the process of sintering and pressing in a negative pressure gas medium. Vacuum sintering can improve the purity of furnace gas and the negative pressure can improve wettability of bonded hard phase. Vacuum sintering has the following advantages: sintering in vacuum condition, hinder greatly reduces the adsorption of gas on the surface of powder and closed pore gas on the densification of the powder, is favorable to the diffusion process, which is conducive to the densification; better able to exclude Si, Mg and Ca in the sintered body trace of oxide impurities thus, to improve the purity of hard alloy; improve the wettability of liquid phase sintering, is conducive to tissue shrinkage and improve the alloy.
