Alumina Overview Alumina films have many excellent material properties, particularly high temperature stability, chemical stability, and low thermal conductivity. Alumina film is now widely used as a wear resistant coating material on cemented carbide inserts. Despite these excellent properties, alumina films have not been widely used in other fields, mainly because today's industry standards are still based on thermal chemical vapor deposition (CVD) processes. Although the CVD process has many advantages, it also has significant disadvantages, namely the high temperature (1000 ° C) required for the process. Hauzer has developed a new process that can deposit alumina by physical vapor deposition sputtering (PVDsputtering) at a standard temperature of 350 ° C to 600 ° C, which greatly expands its application range. Since 2005, when Hauser announced a major breakthrough in the PVD coating of Al2O3 at the European Machine Tool Show EMO, Hauser has started a pilot project with the world's major tool manufacturers and users of alumina die casting molds. The properties of the coating will be discussed below, and the results of this new coating obtained by the deposition of a combination of arc and magnetron sputtering techniques will be described. Tool wear There are several wear conditions in the tool during machining. The tool itself must be able to withstand high temperatures, high pressures, wear and thermal shock. During the cutting process, the cutting edge temperature will exceed 1000 °C. At this high temperature, the adhesive and other components of the tool degrade and cause harmful chemical reactions between the tool and the workpiece. The cutting process is always accompanied by wear and tear, and the pressure at which the tool and the workpiece are in contact with the workpiece is greater than 140 bar (2000 PSI). Thermal shock - the tool is quenching and hot, which is common in milling. The blade heats up during the cutting process and cools as it leaves the cutting face. There is a mechanical shock when milling and cutting intermittently machined surfaces. There are sometimes mechanical shocks during turning, depending on the operating conditions and workpiece conditions. Bond wear occurs when the workpiece is bonded to the tool (which creates a built-up edge). Alumina coating for CVD and PVD Today, CVD alumina coated inserts are widely used in the industry, and the performance of CVD alumina coatings is also widely recognized. Due to the high hardness of alumina (especially at high temperatures), high oxidation temperatures (>1000 ° C), chemical inertness and low thermal conductivity, the performance of alumina coated tools is greatly improved. However, the CVD process usually needs to be performed at a high temperature of 800 ° C to 1000 ° C, which limits the application of the CVD process to the cemented carbide substrate. As the carbide tool becomes brittle, it will result in a decrease in toughness. The PVD process has obvious advantages over the CVD process due to its low deposition temperature of 400 ° C to 600 ° C. The main limiting factor in the fabrication of alumina coatings by the PVD process is that all layers of the interior of the coating system are deposited during the deposition process, including the substrate and bottom pedestal, the target portion of the target etched out of the target, and the inner wall of the vacuum chamber. This will result in instability of the bias supply and the cathode (arc) power supply due to the "poisoning" of the target and the disappearance of the anode. Two techniques that have been successful in solving this problem are: RF (radio frequency) sputtering and BP-DMS (two-pole pulsed dual magnetron sputtering). Alumina coating equipment The PVD alumina system should be capable of depositing minimal gamma-phase alumina at higher deposition rates (short duty cycles) with stable coating characteristics. The system should be able to operate at high temperatures and the cost of the technology itself is not high. It is best to use a single cathode system to upgrade existing equipment to alumina-coated equipment. Hauser's T-Mode control system allows the target surface to be in a transitional state during oxidative deposition, which requires specialized cathode design and unbalanced magnetization within the closed magnetic field. A special control system is used for the best introduction of reactive gases. The system was validated on several production facilities in about two years. Coating optimization The initial work focused on establishing the correct stoichiometric alumina coating point of action. Some parameters affecting the process were studied, such as bias voltage, UBM coil current, temperature, gas partial pressure (argon/oxygen), and cathode power supply. Ion bombardment affects the hardness of the coating, which needs to be handled from the bias, and the bias should be high enough, but below the threshold to avoid argon ion implantation. Since the coating is an insulator, a pulsed bias is used, and the pulse bias can also limit the effect of the arc on the substrate. The bias voltage must be optimized based on the thickness and hardness of the coating. The top layer is obtained by sputter coating and is therefore relatively flat. The underlying coating is obtained by arc coating and its roughness can be detected from the topcoat. The sputter-coated alumina coating is flatter than the alumina coating obtained by arc evaporation because the lower melting point of aluminum tends to produce many droplets, even with pulsed arc evaporation. High hardness alumina requires high ion density to obtain, either dual magnetron sputtering (ie using two cathodes in one device) or using a closed magnetic field layout. In the latter case, the high ion density under plasma conditions is accompanied by a magnetic field that supports unbalanced magnetron. The ion density can be adjusted by the current of the field coil. To form a closed magnetic field, each adjacent UBM coil produces a magnetic field that is opposite in direction. Corresponding cathodes are also designed accordingly. Measuring the change in bias current can measure the degree of enhancement of ionization density. By this method, the coating density is increased and the hardness is also increased. Increasing the coil current increases the bias current until the magnetic field strength is saturated. After reaching the saturation point, increasing the coil current no longer increases the bias current. The saturated condition is reflected in the hardness of the coating. Abrasive Precision Grinding Wheels HANS was the Leading Bonded Grinding Wheel Manufacturers in China.Manufactured a wide variety of Abrasives and Superbrasive products. are a Leading supplier with best quality Products like Grinding Wheel, Cutting Disc, Sanding Belts and Sheets, Brushes and De-burring products, Polishing Pads and Rolls, and much more. Application such as Grinding, Cutting, Sharpening, Polishing, Sanding, Buffing etc. Bonded Grinding Wheel also known as Emery wheel are made up by combining Abrasive Grains by Bonding Process, these grains can are of Aluminum Oxide, Silicon Carbide, Zirconia Alumina 35A, 38A, VSG and many more as per the application. These High Speed cylindrical shaped wheels are used in Grinders, CNC Machines, Lathe Machine etc. We offer wheels starting from 24 mm Diameter to 1075 mm Diameter. To reduce the size of standard bore, a Visor or Bush is used, we offer them with the wheels upon request. Bench Pedestal Grinding Wheels,Abrasive Precision Grinding Wheels,Abrasive Wheels Discs,Internal Grinding Wheel,Roll Grinding Wheels,Ceramic Crankshafts and Camshaft Grinding Wheel Hans Superabrasive Material Co., Ltd. , https://www.hansuperabrasive.com Previous page 1 2 Next page