Wear mechanism of TiN coated carbide and uncoated cermets tools at high cutting speed applications

The wear mechanism of TiN-coated carbide and uncoated cermets tools were investigated at various combinations of cutting speed, feed rate, and depth of cut for end milling of hardened AISI H13 tool steel. The cutting speed is used for semi-finishing and finishing for the said material at high cutting speed regime. The rate of wear growth of the insert was assessed by progressive flank wear using optical microscope by taking photographs after certain length of cut. The wear mechanism at the end of tool life was investigated in detail using scanning electron microscope (SEM). From the photographs of the progressive wear, it has been observed that the time taken for the cutting edge of TiN-coated carbide tools to initiate cracking and fracturing is longer than that of uncoated cermets tools, especially at the combinations of high cutting speed, feed rate, and depth of cut. Whereas, combinations of low cutting speed, feed rate, and depth of cut, the uncoated cermets tools show more uniform and gradual wear on the flank face than that with the same milling conditions of the TiN-coated carbide tools. At low speed, feed rate, and depth of cut, SEM investigation has shown that both inserts experience uniform and gradual wear on the flank face, and diffusion and oxidation have also been observed.