Progress of Super hard Materials in China

       First, the new progress of the binder raw materials

1, ultra-fine iron powder

Refinement of the particle size of the metal powder for activation sintering, reducing the sintering temperature of the product and improve the bonding strength of the diamond bonding strength, improve the processing efficiency of the product, the service life has an important role. Carbonyl iron powder has been used for a long time, but its cost is still high, which is not very economical for some applications that are more emphasis on efficiency requirements. The emergence of ultra-fine iron powder to solve this problem, the iron powder's average particle size of 1.8-2.0μm, the sintering temperature is lower than 900 ℃.

2, pre-alloy powder

Precalcation of metal powders helps to prevent premature loss and segregation of the low-melting-point metal in the sintering process of the metal-bonded products, improves the compactness, uniformity, elastic limit and yield strength of the sintered products, enhances the holding ability of the diamond, and reduces Sintering temperature. In recent years, metal powder pre-alloying technology has attracted attention. For example, geological diamond drill bits made with Cu-Zn-Ni and Cu-Ni-Mn pre-alloyed powders show significant improvements in service life and machining efficiency by 99% and 45%, respectively, over non-pre-alloyed powder drills.

3, ultra-fine toughened polyimide resin powder

Polyimide resin and phenolic resin compared to the high bond strength, high temperature heat (50 ℃ above), dry grinding wheel life expectancy more than doubled. However, the poor toughness of polyimide resin, low bending strength, high cost, to a certain extent, limits its promotion. To change this situation, the average grain size of 30-40μm, the curing temperature of 230 ℃, after toughening modified ultrafine toughened polyimide resin powder, compared with ordinary polyimide resin, its bending Strength increased by 23%, compressive strength increased by 20%.

Progress of Superhard Materials in China

Second, the new development of bonding agent

1, ceramic binder

Low-temperature sintering, high-strength ceramic bonding agent has been one of the topics of research in the industry, the research results in recent years gratifying:

(1) Ceramic bonding agent applied to 80m / s CBN grinding wheel has been put into practical application;

(2) Ceramic bonding agent applied to 120m / s CBN grinding wheel has been successfully developed;

(3) Ceramic bonded grinding tools used in cemented carbide tools, diamond composite sheets, magnetic materials and engineering ceramics have also been developed successfully;

(4) In order to give full play to the advantages of ceramic binder with pores, to achieve the control of stomata, the effect of pore-forming agent on the performance of ceramic bond was studied. The research shows that the strength of the abrasive obtained by adding graphite is affected by the shape, amount and sintering temperature of the graphite particles, and the strength of the abrasive decreases with the increase of the adding amount. However, the strength of the abrasive obtained by adding CaC03 is high, Mostly spherical shape, uniform distribution, with the increase in the amount of pores allowed to increase the size, CaCO3 pore-forming effect better than graphite.

2, sintered metal binder

Our country is a poor country of cobalt metal, so the study of "iron-cobalt" is another hot research topic in our country's diamond tools. In order to improve the performance of iron-based binders, the use of rare earth elements La and Ce has drawn much attention in recent years. The study on the addition of rare earth elements by doping method shows that the iron-based diamond tools developed by this method are close to or slightly more than the cobalt-based diamonds without addition of rare earth in the four indexes of flexural strength, impact toughness, porosity and hardness The corresponding indicator of the tool. The study on the addition of rare earth elements in the form of mixed rare earths showed that the flexural strength and impact toughness of the carcass material increased by 12.4% and 16.6% respectively, while the hardness increased only by 3.2% and the microstructure grains were obviously Refinement, the carcass and diamond combined more closely, greatly increased the height of the diamond blade, the service life increased by 24%.

3, plating metal binder

Similar to the sintered metal bond, the use of rare earth elements in electroplating products is also of concern: the addition of rare earth elements to the Ni-Co plating solution in the form of chlorides has shown that the porosity of the resulting carcass material is significantly reduced and the hardness is significantly increased , Coating dispersion capacity increased by 12% or more, deep plating capacity increased by 20% or more, plating speed greatly improved.

At the same time, the research on low-cobalt electroplating formula has also made progress. The study of Ni-Co-Mn replacing Ni-Co shows that the Co content in the plating solution is decreased from 30% to 5%, and 0.1% Mn, the hardness and strength of the coating is higher than that of Ni-Co, the toughness is obviously reduced, the electroplated diamond tools are used for gemstone carving more sharply and more durable than Ni-Co, and the production cost is reduced.