Electroplated diamond tools multi-channel processes involved in the manufacturing process, any process inadequate, will cause the coating off.
Steel substrate in the treatment step before entering the plating tank is referred to as pre-plating treatment. Pre-treatment: mechanical polishing, degreasing, etching and activation steps. The purpose of the pre-plating processing is to remove the surface of the base of the burr, grease, oxide film, rust and oxide scale, normal growth, the formation of the binding force between the molecules to expose the base metal of the metal lattice. If handled properly, before plating the surface of the substrate has a thin oil film and the oxide film, the metal lattice of the base metal can not be sufficiently exposed, it will hinder the binding force between the metal coating of the bath
Formulations of the bath directly affect the kind of plating metal, hardness, wear resistance, with different process parameters also control the thickness of the plating metal crystals, caused by the density and the size of the plating internal stress. For the production of electroplated diamond tools,abrasive tools, most of the nickel or nickel - cobalt alloy, fails to consider the impact of bath impurities, and the factors that affect the coating off:
1) affect the coating of the internal stress of the internal stress is generated in the electro-deposition process, the solution of the additives and their decomposition products and hydroxides will increase the internal stress. Such stress is in the plating process, plating layer by some deposition factors, caused due to lattice defects. In particular the role of certain metal ions and organic additives, will significantly increase the internal stress of the coating. Macroeconomic stress and micro-stress two types of coating internal stress. Macroscopic stress is manifested in a sheet metal plating on one side, bending flakes impact of stress within the coating. Microscopic stress is manifested mainly by increasing the hardness of the coating.
Macroscopic stress can cause the coating to produce bubbles, cracking, loss and other phenomena in the storage, grinding wheel,use process.
Different plating bath for electroless nickel or nickel - cobalt alloy composition, internal stress are significant differences between the higher chloride content, the greater the internal stress. For the main salt of nickel sulfate plating bath, bath internal stress watt class were less than other types of plating solution. By adding an organic brightener, or stress relieving agent the macro internal stress of the coating may be significantly reduced while increasing its microscopic internal stresses. Different process combinations, such as current density, pH value, temperature, and can make the same kinds of bath of the coating have different internal stress. Therefore, to reduce the influence of the internal stress must strictly control the scope of the process of the bath, so as to ensure that the internal stress of the coating in the range of the process requirements.
2) the impact of hydrogen evolution in any plating solution, regardless of how the PH value, due to the water molecule dissociation, always present a certain amount of hydrogen ions. Accordingly, under appropriate conditions, both in acidic, neutral or alkaline electrolyte solution for electroplating with a metal precipitated on the cathode, while often hydrogen precipitated. Hydrogen ions in the cathodic reduction, part of the formation of hydrogen gas to escape, the part of the state of atomic hydrogen to penetrate the base metal and coating. So that the lattice distortion causing great stress, but also the coating significantly deformed. At this point, no defects from the appearance point of view, but it's mechanical performance is substandard. Adsorbed hydrogen will swell so the tool during use, when the temperature of the surrounding medium is increased, aggregation in the matrix metal or plating metal plating bubbled off phenomenon.
The electroless nickel cathode current efficiency of 95%, only 5% of the hydrogen evolution reaction. However, if the temperature is too high, the PH value is too low, the components improper causes the hydrogen evolution exacerbate. Therefore, how to control the plating hydrogen evolution reaction control coating internal stress is a problem worth exploring.
Polycrystalline diamond compact the PCD (PolyCrystalline Diamond) layer and carbide substrate. The PCD layer has high hardness, carbide substrate with good toughness, a combination of both the PCD composite sheet widely used in cutting, wood processing, and drilling industries. The PCD tool making in a variety of ways, largely based on the heating mode, the use of solder or not to divide. Heating plays a decisive role in the production process, the choice of solder a significant impact on the design of welded joints of the structure is also an important means to improve the quality of welding quality. Therefore become a key technology in the manufacturing process of PCD tools, welding.grinding wheel
The welding PCD composite sheet essentially is the welding of the cemented carbide substrate and the toolholder support member. Multi-Mn-based solder of carbide welding, brazing temperature of about 1000 ℃. However, the heat resistant temperature of the PCD layer is generally not more than 700 ℃, otherwise it will cause thermal damage of the PCD layer, reducing the performance of the tool after welding using. Must therefore be to find a both reduce the temperature of the brazing, but also at the same time to ensure a sufficient welding strength welding method. PCD composite sheet welding method of laser welding, vacuum diffusion welding, vacuum brazing, a high-frequency induction brazing, cooled brazing, an inert gas protection brazing. Weld strength is sufficient, but the high cost of some equipment used, maintenance costs, and complex process, not easy production operation, greatly increased the production costs of the PCD composite piece tool, and is not conducive to the promotion and application of the PCD tool. In this paper, a comparative analysis of the advantages and disadvantages of various PCD composite sheet welding method.abrasive wheel