Titanium-carbon compound of dark gray color and a melting point of 3170 °C and special hardness (3200 HV). As a sintering product, it is used together with nickel and cobalt for indexable inserts in metal cutting tools and for wear-resistant coatings.
Titanium as a major carbide former reduces the temperature of the iron-graphite eutectic in iron-carbon alloys simultaneously increasing the temperature of the iron-carbideeutectic, i.e. the interval between both temperatures is reduced (figure 1).
Usually, graphitizing elements migrate towards the solid phase (austenite) and carbide formers towards the liquid phase (residual melt). Since carbide formers accumulate in the liquid phase and accordingly, graphitizing elements deplete in the liquid phase more and more, the eutectic temperature of the iron-carbideeutectic in the residual melt is continually increased. At the same time, the temperature in the iron-graphite eutectic in the residual melt is lowered, since the melt is depleted of graphitizing elements as a result of segregation towards austenite. The consequence is the formation of carbide.
Even low titanium contents (from 0.02%) in cast iron trigger the formation of titanium carbides or titanium carbonitrides in the form of cubic inclusions with hardness values which may exceed 1800 HV (see Vickers hardness test) (figure 2 and 3) thus considerably affecting mechanical processing.
Carbidic cast iron
Annealing for carbide decomposition