How to prepare the workpiece coating of tungsten carbide?
In many cases, the finished part needs to be coated. The coating provides lubricity and increased hardness, and provides a diffusion barrier to the substrate that prevents oxidation when exposed to high temperatures. The tungsten carbide matrix is critical to the performance of the coating. In addition to the main characteristics of the custom matrix powder, the surface properties of the substrate can be tailored by chemical selection and modification of the sintering process. Through the migration of cobalt, more cobalt can be enriched in the outermost layer of the blade surface in the thickness of 20-30 μm relative to the rest of the workpiece, thereby imparting better toughness to the surface layer of the substrate, so that it has strong resistance to deformation.
Tool manufacturers based on their own manufacturing processes (such as dewaxing methods, heating rates, sintering times, temperatures, and carburizing voltages) may impose special requirements on the grades of carbide powder used. Some toolmakers may sinter workpieces in vacuum furnaces, while others may use hot isostatic pressing (HIP) sintering furnaces (which pressurize the workpiece near the end of the process cycle to eliminate any residue). Pore). The workpiece sintered in the vacuum furnace may also need to be subjected to a hot isostatic pressing process to increase the workpiece density. Some tool manufacturers may use higher vacuum sintering temperatures to increase the sintered density of mixtures with lower cobalt content, but this approach may make the microstructure coarse. In order to maintain a fine grain size, a powder having a smaller tungsten carbide particle size may be used. In order to match the specific production equipment, dewaxing conditions and carburizing voltage also have different requirements on the carbon content of the tungsten carbide powder.
All of these factors have a critical impact on the microstructure and material properties of the tungsten carbide tool that is sintered. Therefore, there is a need for close communication between the tool manufacturer and the powder supplier to ensure that it is manufactured according to the tool. Customized production process custom grade tungsten carbide powder. Therefore, it is not surprising that there are hundreds of different carbide grades. For example, ATI Alldyne produces more than 600 different powder grades, each of which is specifically designed for the intended user and specific use.