Metal powder quality is an important factor in determining the sintering process and finished product performance of metal-bonded diamond tools. There are many performance indicators that characterize the quality of metal powders. Among them, several indicators such as oxygen content, particle size, and loosening ratio have a significant impact on practical applications and directly determine the uniformity of the tool mixture, cold pressing formability, and cold pressing density. , sintering degree, sintering density, sintering hardness, flexural strength, diamond holding power of the matrix and a series of performance indicators such as the wear performance of the matrix. From the perspective of actual application effects, the impact of powder oxygen content on diamond tools is the primary factor.

​The influence of powder oxygen content on diamond tools is as follows:

​1. Effect on cold press formability

​The higher the oxygen content, the worse the cold press formability: The main reason is that metal oxides will harden the powder and reduce the toughness, which is detrimental to the press formability. Especially when the oxygen content on the powder surface is too high, the powder adhesion will increase. Large, it reduces the meshing strength between powder particles during pressing, making the cold press formability worse. In actual production, when the mixing amount is large, cold press molding is often prone to deterioration after the powder is not used up and stored for a period of time. This is mainly related to the oxidation of the powder, especially in humid climate conditions, the problem is more prominent.

​2. Effect on sintering temperature and process stability

​The higher the oxygen content, the higher the sintering temperature of the matrix and the worse the sintering stability. This is because metal powder oxides, especially surface oxides, greatly reduce the surface activity of powder particles, seriously hinder the interfacial bonding state between powder particles during the sintering process, hinder the alloying process, reduce the interfacial bonding strength between particles, thereby reducing It improves the matrix’s holding power on diamonds.

​Experimental results show that the higher the oxygen content, the higher the sintering temperature, the lower the densification degree of the sintered body, the greater the loss rate of low melting point materials, and the performance of the matrix deteriorates.

​The existence of surface oxide hinders the interfacial bonding and alloying between metal powder particles during the sintering process, affecting the sintering densification process.

​3. Effect on the sintering strength of the matrix

​Under the same sintering temperature and pressure, the higher the oxygen content, the lower the sintering strength of the carcass.

​The higher the oxygen content of the metal powder, the worse the cold pressing density. There are many "bridging" holes in the compact, which are difficult to eliminate during sintering.

​4. Effect on the hardness of the sintered matrix

​The hardness of the sintered matrix is ​​mainly related to the properties of the metal powder particles, structural uniformity, interface bonding strength and densification degree (porosity). The oxygen content of metal powder has no significant effect on the hardness of sintered samples. If the oxides inside the powder are distributed in a dispersed state, it will increase the lattice distortion energy inside the powder particles and increase the hardness of the particles.

​5. Effect on carcass tissue and compactness

​Oxygen content, especially the oxygen content on the surface of powder particles, has a great influence on the structure and density of the sintered matrix. The lower the oxygen content, the better it is to obtain a matrix with good uniformity, strong particle interface bonding force, and high degree of densification. structure, which is conducive to improving the mechanical holding power of the matrix to diamond.

​6. Effect on carcass alloying

​Methods of alloying between sintered matrix powders:

​First, it relies on low melting point materials (Sn, Zn, etc.) to melt and diffuse and dissolve at the particle interface to form a solid solution, intermediate phase or compound.

​Second, the mutual diffusion between solid particle interfaces. The influence of sintered matrix on diamond holding force:

​The higher the oxygen content of the metal powder, the worse the alloying effect of the sintered matrix, the worse the comprehensive mechanical properties of the matrix, and the worse the mechanical holding power of diamond.

​Experiments show that when the oxygen content of Fe powder exceeds 5000×10-6, the diamond enclosing ability of the matrix becomes poor, mainly due to insufficient alloying between powders, loose matrix, and insufficient densification. Especially when the oxygen content exceeds 7000×10-6, an extremely loose "tofu dregs"-like structure will appear in the sintered matrix structure, losing the ability to hold diamonds.