Liquid phase sintering of tough coated hard particles

Abstract Tough coated hard particles (TCHP) are a new microstructure opportunity for designing hard, wear resistant materials at the particle level. As opposed to coating whole devices, TCHP particles are coated at the micrometer level. During wear, these particles constantly present fresh, wear–resistance microstructures that provide a service lifetime not possible with coated devices. Further, fracture toughness is maximized by the uniform tough ligament spacing between hard particles. Such functionality has applications in abrasive wear, wire drawing, metal forming, rolling contacts, and other applications requiring performance over long service times. For the TCHP concept to succeed, new protocols are required for densification during liquid phase sintering. To avoid grain coarsening, dissolution of the coating phase must be minimized while at the same time densification is induced. This unique challenge reduces the amount of densification possible via solution-reprecipitation processes. Thus, special coatings and composition combinations may be required to control densification while preserving the desired coating–core microstructure in the densified product.