1. The application of brazing technology in the application of diamond tools
The high hardness and excellent physical and mechanical properties of diamond make diamond tools an indispensable tool for processing all kinds of hard materials. The adhesion of the carcass metal base to diamond (the inclusion of the carcass) is one of the main factors affecting the service life and performance of the diamond tool.
Due to the high interfacial energy between diamond and common metals and alloys, the diamond particles cannot be infiltrated by the general low melting point alloy, and the adhesion is extremely poor. In the traditional manufacturing technology, the diamond particles are only cooled by the carcass. The resulting mechanical clamping force is embedded in the base metal matrix without forming a strong chemical bond or metallurgical bond, which results in the diamond particles being easily separated from the carcass metal base during operation, greatly reducing the life and performance level of the diamond tool. Most of the impregnated tools have a low utilization rate of diamonds, and a large amount of expensive diamonds are lost in the work and lost in the waste. Lin Zengdong and others took the lead in using diamond surface metallization technology to impart many new characteristics to the diamond surface, such as excellent thermal conductivity and thermal stability, improving its original physical and chemical properties, and improving its wettability to metal or alloy solutions.
The metallization of diamond surface has attracted great attention from the diamond tool manufacturing industry at home and abroad in the 1970s. Many people are committed to the study of diamond surface metallization during the sintering process, adding or pre-bonding a strong carbide metal powder to the diamond surface (this diamond is not chemically etched before it is heated). The reaction can only belong to the diamond coating) in order to achieve their chemical bonding to the diamond during the sintering process. Although the literature has demonstrated that some metals such as tungsten (not oxidized) can form a WC layer on the diamond surface at lower temperatures (around 800 ° C), from the process used to achieve pre-metallization of the diamond surface, vacuum is required. Under the conditions, heating at 600 ° C or more for 1 hour can obtain the desired bonding force. According to the sintering conditions of the commonly used impregnated diamond cutting tools, heating at 900 ° C for less than 5 minutes in a non-vacuum or low vacuum is unlikely to form a metallized layer on the diamond surface. Because whether the active metal atom (Ti, V, Cr, etc.) is enriched to the diamond surface or the interfacial reaction reaches the bonding of the binder and diamond metallurgy, it is an atomic diffusion process. According to the temperature used for hot pressing and such a short time, this process is extremely inadequate. Under solid phase sintering conditions (sometimes with a small amount of low strength, low melting point metal or alloy liquid phase), the chemical bonding or metallurgical bonding of the carcass to diamond is very weak or not formed at all.
Pre-metallization of the diamond surface is not the ultimate goal, but only one of the measures that are expected to achieve a chemical metallurgical bond with the carcass metal. After the plated diamond is sintered into a saw (drill) tooth, the exposed diamond on the folded section loses the coating, and the surface of the residual pit that has fallen off the diamond is very smooth. This phenomenon seems to indicate that the diamond and the carcass are still Failure to reach the level of chemical inclusion. Therefore, even if the surface pre-metallization of diamond is realized, the conventional solid phase powder metallurgy sintering method cannot realize a firm bond between the diamond and the carcass material.
At the end of the 1980s, people began to explore brazing technology for diamond tool making. Some transition group elements (such as Ti, Cr, W, etc.) are plated on the diamond surface and chemically reacted with them to form carbides on the surface. Through the action of this layer of carbide, the diamond, the binder and the matrix can achieve a firm chemical metallurgical bond by brazing, thereby realizing the true metallization of the diamond surface, which is the principle of diamond brazing. As can be seen from the published patents and articles, this technology can make the maximum edge value of diamond reach 2/3 of the particle size, and the tool life can be increased by more than 3 times, while the conventional value is less than 1/3, allowing the edge value to be opened. The blade operation is obtained when the blade value is stabilized. Therefore, the use of brazing technology is expected to achieve a strong bond between the carcass metal (solder) and the parent material - diamond and steel substrate.
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