Progress of products made of superhard materials in China

       The new progress of binder raw materials

1. Superfine iron powder

Refining the particle size of metal powder plays an important role in activating sintering, reducing the sintering temperature of the products, improving the bonding strength of diamond, improving the processing efficiency and service life of the products. Carbonyl iron powder has been used for a long time, but its cost is still high, and it is not very economical for some applications which emphasize the efficiency. The emergence of ultrafine iron powder to solve this problem, the average particle size of the powder Fisheri reached 1.8 - 2 m, the sintering temperature is lower than 900 DEG C.

2. Pre alloyed powder

Metal pre alloy powder to prevent metal bond products in low melting point metal loss and premature segregation in sintering process, improve sinter density and uniformity, elastic limit and yield strength, enhance the ability to diamond, and reduce the sintering temperature. In recent years, the technology of metal powder pre alloying has attracted much attention. For example, using Cu - Zn - Ni and Cu - Ni - Mn pre alloyed powder to manufacture geological diamond bit, its service life and processing efficiency are improved by 99% and 45% respectively compared with non pre alloyed powder bit, and the effect is obvious.

3. Superfine toughened polyimide resin powder

Compared with phenolic resin, polyimide resin has higher adhesive strength, higher heat resistance temperature (above 50 degrees), and more than 1 times of life of grinding wheel under dry grinding condition. But polyimide resin has poor toughness, low bending strength and high cost, which limits its popularization and application to a certain extent. In order to change this situation, the ultra-fine toughened polyimide resin powder with average particle size of 30 - 40 m, curing temperature of 230 degrees and toughening modification was developed. Compared with common polyimide resin, its flexural strength increased by 23%, and compressive strength increased by 20%.

Progress of products made of superhard materials in China

Two. New progress in bond research

1. Ceramic bond

Low temperature sintering and high strength ceramic bond has been one of the key topics in the industry, and the research achievements have been gratifying in recent years:

(1) vitrified bond applied to 80m / sCBN grinding wheel has been put into practical application;

(2) the vitrified bond applied to 120m / sCBN grinding wheel has been developed successfully;

(3) ceramic bonded abrasives used in cemented carbide tools, diamond composites, magnetic materials and engineering ceramics have also been developed successfully;

(4) in order to give full play to the advantages of ceramic binder with porosity, and to achieve the control of porosity, the effect of pore forming agent on the performance of ceramic binder was studied. The study shows that adding abrasive strength of graphite prepared by effect of graphite particle shape, dosage, sintering temperature, and increase the bending strength with the addition amount decreased; while adding abrasive strength of CaC03 prepared by high generation stomatal shape are spherical, uniformly distributed within the permitted range with the amount of the increase of pore size increases and the pore ratio of CaCO3 graphite good effect.

2. Sintered metal bond

China is a poor country of cobalt metal, so the study of "iron substituting cobalt" is another hot spot of diamond tools research in china. In order to improve the properties of iron-based binders, the application of rare earth elements La and Ce has attracted much attention in recent years. Study on addition of rare earth elements in doping method showed that the method developed by the iron-based diamond tools, the corresponding index is close to or slightly more than without rare earth in bending strength, impact toughness, hardness and porosity of the 4 indicators of the cobalt diamond tools. Study on addition of rare earth elements to form the mixed rare earth shows that 12.4% and 16.6% to improve the bending strength and impact toughness of the matrix material respectively, and the hardness increased only 3.2%, the microstructure of matrix and diamond grain refinement, with more closely, protrusion height of diamond is greatly increased, the service life is increased by more than 24%.

3. Electroplating metal bond

Similar to the sintering of metal bond, application of rare earth elements in electroplating products are also of concern: the rare earth elements in the form of chloride to Ni -- Co of the bath in the show that the matrix material made of pores decreased, increased hardness, coating dispersion capacity increased by more than 12%, the deep plating ability is improved by more than 20%, the speed of plating in order to improve.

At the same time, the research progress of low cobalt plating formula, based on Ni - Co - Ni - Mn instead of Co show that the Co content in the plating solution formula will decrease from conventional 30% to 5%, and about 0.1% Mn, the hardness of the coating and the intensity ratio of Ni - Co higher toughness decreased significantly, electric gold plated diamond tools for stone carving are more durable than the Ni Co more sharp, production, and production cost reduction.