US Patent 7435487 Hard film and hard film-coated tool

A hard film formed by an arc-discharge ion-plating method, having a composition comprising metal components represented by AlxCr1−x−ySiy, wherein x and y are respectively atomic ratios meeting 0.45≦x≦0.75, 0≦y≦0.35, and 0.5≦x+y<1, and non-metal components represented by N1−α−β−γBαCβOγ, wherein α, β and γ are respectively atomic ratios meeting 0 ≦α≦0.15, 0≦β≦0.35, and 0.003≦γ≦0.25, the hard film having an NaCl-type crystal structure, with a half width of 2θ at an X-ray diffraction peak corresponding to a (111) face or a (200) face being 0.5-2.0°, and the hard film containing oxygen more in grain boundaries than in crystal grains.