Ultrafine WC-Co cemented carbide end mills prepared by spark plasma sintering and wear mechanism in milling of AISI H13

Ultrafine tungsten carbide (WC)-cobalt (Co) and WC-(Ti,W)C-Co end mills were produced via spark plasma sintering. The wear mechanism of these end mills during machining of AISI H13 steel was investigated. WC-Co exhibits good mechanical properties (HV30: 2110 kg/mm2, KIC: 10.4 MPa/m1/2, TRS: 1990 MPa). Although the high hardness of WC-Co makes it show excellent resistance to abrasive wear, it suffers from a significant adhesion problem. As the cutting temperature increases, the oxidation of the WC-Co causes damage to the microstructure of tool materials, which deteriorates the grain boundary strength and promotes adhesive wear. This phenomenon causes large areas of tool materials to chip off and eventually results in cutting-edge breakage. The high brittleness of (Ti,W)C causes cracks to propagate at low-stress levels, reducing the mechanical properties of WC-(Ti,W)C-Co (KIC: 8.8 MPa/m1/2, TRS: 1090 MPa). However, (Ti,W)C addition enhances the resistance to oxidation and workpiece adhesion, which reduces the tool material loss caused by adhesive wear. The tool life of WC-(Ti,W)C-Co is three times longer than that of WC-Co in milling of AISI H13 at the same cutting speed. The key to maximizing the mechanical properties of ultrafine cemented carbide tools when machining AISI H13 is the modification of anti-adhesive wear of surface.