A gas turbine engine includes a rotor that has a rim, blades extending radially outwards from the rim, a hub extending radially inwards from the rim, an arm extending axially from the rim, the arm having a radially outer surface, and a coating disposed on the radially outer surface. The coating is zirconia-toughened alumina in which the alumina is a matrix with grains of the zirconia dispersed there through. The grains of zirconia are predominantly a tetragonal crystal structure.