In hypereutectoid steels the proeutectoid cementite in austenite exhibits different morphologies. Cementite precipitates at the grain boundaries as separate grains, continuous films and allotriomorphs, and appears in the matrix as Widmanstätten side-plates, intragranular Widmanstätten plates and intragranular idiomorphs [11], [12] and [13]. The allotriomorphic cementite precipitates at the grain boundaries at high temperatures. Both Widmanstätten side-plates and intragranular Widmanstätten plates exist in the austenite at low temperatures. For the co-existence of grain boundary precipitates and the Widmanstätten plates at the intermediate temperature range, Widmanstätten carbide plates normally form before pearlite and after the grain boundary precipitates [11]. Grain boundary carbides exist in all hypereutectoid steels.