At present, there are four main processing methods of diamond film coated tools:, thick film diamond cutters, diamond tools and single crystal diamond cutter.
The 2.1 film coated tools
Film coated tools is in rigid and high temperature properties of collective materials by chemical vapor deposition (CVD) cutting tools made of diamond thin films.
Because the Si3N4 ceramics, WC-Co alloy and metal W thermal expansion coefficient close to produce films and diamond, the small thermal stress, which can be used as a knife body base material. WC-Co alloy, bonded phase Co are apt to be formed between diamond film and substrate of graphite and reduce the adhesion strength, pretreatment before deposition needed to eliminate the influence of Co (usually by acid corrosion to Co).
Chemical vapor deposition method is the use of certain methods to gas containing C source activation, in the gas low pressure, so that the carbon atoms in a certain area down deposition, carbon atoms in condensed, forming a diamond. The CVD method for deposition of diamond mainly includes: microwave, hot filament, DC arc spraying method etc..
The advantages of diamond films can be applied to various complicated tool, such as a cutting blade, milling cutter, reamer and bit; can be used for cutting many non metal materials, the cutting force is small, small deformation, stable work, slow wear, the workpiece is not easy deformation, suitable for finishing on the workpiece material, narrow tolerances. The main drawback is the diamond film and substrate adhesion is poor, does not have the diamond film tool grinding.
2.2 diamond thick film tool
Diamond thick film production process tool generally include: large area diamond film preparation of diamond film; cut into shape tool needs; welding diamond thick film and substrate material; grinding and polishing of diamond thick film tool cutting edge. (1) preparation and cutting diamond thick film
Process for preparing diamond film is commonly used by method of DC plasma jet CVD. The diamond deposition onto WC-Co alloy (mirror surface), the cooling process of matrix, diamond film automatically fall off. This method fast deposition speed (up to 930 μ m/h), lattice combination more closely, but growth relatively rough surface. Diamond film with high hardness, wear resistance, non conducting determines cutting method it is laser cutting (cutting can be carried out in air, oxygen and argon environment). The laser cutting can not only the diamond thick film cut into the shape and size required, but also cutting tool post angle, with narrow cuts, high efficiency advantages
(1) welding diamond thick film tool
Very high interfacial energy between diamond and metal and its alloy in general, diamond cannot be of low melting point alloy by general infiltration, poor solderability. At present mainly by adding strong carbide in copper silver alloy solder forming elements or to improve between diamond and metal weldability by metallization of diamond surface.
The active metal brazing method
Copper silver alloy solder generally with Ti, without flux welding in an inert gas or vacuum. Ag=68.8wt%, solder composition of commonly used Cu=26.7wt%, Ti=4.5wt%, preparation method used is the arc melting method and powder metallurgy method. Ti as the active element in the process of welding and C reflects the generation of TiC, can improve the wettability and adhesive strength of diamond and solder. The heating temperature is 850 ℃, heat 10 minutes, slowly cooling to reduce internal stress.
The surface of the metal after welding
Surface metallization of diamond is the metal plating on diamond surface by surface treatment technology, the performance of the surface with a metal or metal. The general is Ti plating on diamond surface, Ti reacts with C to form TiC, TiC and Ag-Cu alloy solder wetting and bonding strength better. At present, Ti methods commonly used are: vacuum physical vapor deposition (PVD, including vacuum evaporation plating, vacuum sputtering plating, vacuum ion plating and so on), chemical vapor deposition and sintering powder covering. PVD single coating is low, diamond plating process temperature lower than 500 ℃, between coating and diamond is the physical attachment, no chemical metallurgy. CVD Ti and diamond chemical reaction to form a strong metallurgical bonding, high reaction temperature, damage of diamond.
(2) thick film diamond cutting tool grinding
Processing method of diamond thick film tool: mechanical grinding, hot metal disc grinding, ion beam, laser beam and plasma etching.
2.3 sintered diamond tools
The method of diamond thick films with rolling grinding damage processing into the average particle size of 32 ～ 37 μ m diamond grains or directly by means of high temperature high pressure process of diamond grain, the grain powder piling up to WC-16wt%Co alloy, which is then isolated using Ta foil, 5.5GPa, 1500 ℃ sintering 60 minutes, made of sintered diamond, tool made of the sintered body has a very high wear resistance
The 2.4 single crystal diamond cutter
Single crystal diamond cutter is usually the diamond crystal is fixed on the knife head, a knife head with screw or plate fixed on the lathe tool bar. Fixed method in the knife head of diamond are: mechanical reinforcement method (the diamond bottom surface and pressurized surface smooth, with plate compression fixed on the knife head); powder metallurgy (the diamond on the alloy powder, the sintering in vacuum, the diamond is fixed on the knife head); bonding and brazing method (using inorganic binder or other adhesive fixed diamond). Because the expansion coefficient of the thermal difference between diamond and matrix, diamond is easy to loose, fall off.
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