The combination of black and metallic shiny surfaces is interesting for aesthetic applications in jewelry and watch industry. Stainless steel and black zirconia provide this effect, but due to the differing hardness polishing is difficult und results in uneven surfaces which are unsuited to the high standards of aesthetic products. Providing a non-magnetic joining partner with comparable hardness to zirconia is the approach that directed the focus to cermets. REACH health regulations demand for products in contact with human skin to stay below a nickel release rate of 0.5 µg/cm2/week. Therefore, an iron-based metal matrix was chosen to bind the hard TiCN particles. Two-component injection molding was applied to shape the samples since this technology allows for complex geometries. For co-sintering, thermal expansion coefficient and sintering behavior had to be adjusted which includes the modification of the black zirconia powder.
Mannschatz et al. (Fri,) studied this question.