High-speed steel (HSS) consists of Fe and several kinds of transition metal carbides. This steel is applied to cutting tools and as wear-resistant materials. When used as a cutting tool, HSS experiences relatively high thermal shock because a coolant such as water or oil is flowed over the surface of the heated HSS. The purpose of this research is to increase the hardness, strength, fracture resistance and thermal shock resistance of HSS. A possible strategy is to incorporate a hard ceramic material of high strength into an HSS matrix. This paper describes the molten state processing of such a composite with oriented unidirectional alumina fibers (10 mm diameter) - HSS system. The HSS powder layer (5 mm or 1 cm) and the fiber layer (195 mm) were alternatively inserted at 2 or 20 vol% fibers in a carbon mold and heated at 1630oC for 5 minutes in an Ar atmosphere to melt the HSS. During the heating, phase separation of the composite occurred to form an upper layer of fibers and a lower layer of the molten HSS. This phenomenon resulted from the density difference and low wettability between the two components. The solidified HSS of 90.5% theoretical density was made of pearlite (a mixture of Fe3C and a-Fe) and transition metal carbides, and provided a high Vickers hardness of 9.14 GPa. On the other hand, our previous study revealed that the hotpressing of laminated green composites under a pressure of 39 MPa at low temperatures of 900o-1100oC produced homogeneous dense structures without phase separation. The combination of the results derived in the above two processings leads to the conclusion that the key factors to produce dense laminated composites are the control of the heating temperature and applied pressure.

Keywords: High-speed steel, Alumina fiber, Pearlite, Transition metal carbide, Vickers hardness, Wettability