Appearance classification and type introduction of diamond saw blades

At present, there are four main processing methods of diamond saw blades: thin-film coating tools, thick-film diamond welding tools, diamond sintered body tools and single crystal diamond tools.

2.1 Thin-film coated tools

Thin-film-coated tools are tools made by chemical vapor deposition (CVD) deposition of diamond thin films on collective materials with good rigidity and thermal properties.

Since the thermal expansion system of Si3N4 series ceramics, WC-Co series cemented carbide and metal W is close to that of diamond, the thermal stress generated during film formation is small, so they can be used as the base material of the cutter body. In WC-Co cemented carbide, the presence of the binder phase Co is easy to form graphite between the diamond film and the matrix, which reduces the adhesion strength. It needs to be pretreated before deposition to eliminate the influence of Co (usually by acid etching to remove Co) .

The chemical vapor deposition method uses a certain method to activate the gas containing the C source, and under the extremely low gas pressure, the carbon atoms are deposited in a certain area, and the carbon atoms form a diamond phase during the condensation and deposition process. At present, the CVD methods used to deposit diamond mainly include: microwave, hot filament, DC arc spray and so on.

The advantage of diamond film is that it can be applied to various geometrically complex tools, such as inserts with chips, end mills, reamers and drills; it can be used to cut many non-metallic materials, with small cutting force, small deformation, The work is stable, the wear is slow, and the workpiece is not easily deformed. It is suitable for finishing with good workpiece material and small tolerance. The main disadvantage is that the adhesion between the diamond film and the substrate is poor, and the diamond film tool does not have regrindability.

2.2 Diamond thick film welding tool

The production process of diamond thick film welding tools generally includes: preparation of large-area diamond film; cutting the diamond film into the shape and size required by the tool; welding of the diamond thick film and the tool base material; grinding and polishing of the cutting edge of the diamond thick film tool . (1) Preparation and cutting of diamond thick film

A commonly used process for preparing diamond thick films is DC plasma jet CVD. The diamond is deposited on the WC-Co alloy (the surface is mirror-finished), and the diamond film automatically falls off during the cooling of the substrate. This method has a fast deposition rate (up to 930 μm/h), and the bonding between the lattices is relatively tight, but the growth surface is relatively rough. The hardness, wear resistance and non-conductivity of diamond film determine that its cutting method is laser cutting (cutting can be carried out in the environment of air, oxygen and argon). The use of laser cutting can not only cut the diamond thick film into the required shape and size, but also cut out the relief angle of the tool, which has the advantages of narrow slit and high efficiency.

(1) Welding of diamond thick film tools

The interface energy between diamond and general metals and their alloys is very high, so that diamond cannot be infiltrated by general low melting point alloys, and the weldability is extremely poor. At present, the weldability between diamond and metal is mainly improved by adding strong carbide forming elements in copper-silver alloy solder or by metallizing the diamond surface.

① Active solder method

The solder is generally made of copper-silver alloy containing Ti, and soldered in inert gas or vacuum without flux. The commonly used brazing filler metals are Ag=68.8wt%, Cu=26.7wt%, Ti=4.5wt%, and the commonly used preparation methods are arc melting and powder metallurgy. As an active element, Ti reacts with C to form TiC during the welding process, which can improve the wettability and bonding strength of diamond and solder. The heating temperature is generally 850 ° C, the temperature is kept for 10 minutes, and the cooling is slow to reduce the internal stress.

②Welding after surface metallization

The metallization of the diamond surface is to coat the diamond surface with metal through surface treatment technology, so that the surface has the properties of metal or metal-like. Generally, Ti is plated on the surface of diamond, and Ti reacts with C to form TiC. TiC and Ag-Cu alloy brazing filler metal have good wettability and bonding strength. At present, the commonly used titanium plating methods are: vacuum physical vapor deposition (PVD, mainly including vacuum evaporation plating, vacuum sputtering, vacuum ion plating, etc.), chemical vapor plating and powder coating sintering. The PVD method has a low single plating amount, the temperature of the diamond during the plating process is lower than 500 ° C, and the plating layer and the diamond are physically attached and have no chemical metallurgy. The chemical reaction between Ti and diamond by CVD method forms a strong metallurgical bond, and the reaction temperature damages the diamond.

(2) Sharpening of thick film diamond tools

The processing methods of diamond thick film tools include: mechanical grinding, hot metal disk grinding, ion beam, laser beam and plasma etching.

2.3 Diamond sintered body tool

The diamond thick film is processed into diamond grains with an average particle size of 32~37μm by the method of rolling grinding damage, or the diamond grains are directly obtained by the warm pressing method, and the grain powder is stacked on the WC-16wt%Co alloy, and then used Ta foil isolates it and sinters it at 5.5GPa and 1500℃ for 60 minutes to make a diamond sintered body. The turning tool made of this sintered body has very good wear resistance.

2.4 Single crystal diamond tools

The single crystal diamond tool usually fixes the diamond single crystal on the small cutter head, and the small cutter head is fixed on the turning tool holder with screws or pressure plates. The main methods of fixing diamond on the small cutter head are: mechanical reinforcement method (grinding the bottom surface and pressing surface of the diamond, and pressing and fixing it on the small cutter head with a pressure plate); powder metallurgy method (putting the diamond in the alloy powder, adding Pressed in a vacuum and sintered to fix the diamond on the small cutter head); bonding and brazing methods (using inorganic binders or other binders to fix the diamonds). Because the thermal expansion coefficients of the diamond and the matrix are very different, the diamond is easy to loosen and fall off.