The influence of titanium addition on wettability of high-chromium white cast iron-matrix composites

The mining industry exerts ever increasing demand for components with high wear resistance to the extent that plain ferrous alloys are falling short. Innovative metal-matrix composites non-ferrous metals have been widely researched and used. Casting composites based on ferrous alloys pose monumental challenges in casting. First, the density differential results in large buoyant forces on the ceramic such that unless a rigid structure is configured, the less dense ceramic floats on the metal stream. Second, the poor wetting properties between metal and ceramic will result in inferior bonding of the matrix, hence separation of solids in service. The paper attempts to improve the bonding characteristics of zirconia and alumina through wettability studies. High-chromium white cast iron was used as a substrate. The wetting behavior of molten iron on the substrates of zirconia and alumina was investigated. The study shows that alumina is poorly wetted with copper and nickel; the wetting angles were higher than 90°. Thus, the envisaged coating of alumina with copper or nickel prior to casting of ferrous melts will not significantly alter or improve wettability of alumina. Between copper and nickel, nickel has better bonding with alumina than copper. Titanium in high-chromium white cast iron was found to improve the wetting characteristics on alumina. The wetting angle decreased with increased titanium content.