Hard coating film for cutting tool
The present invention relates to a hard coating including an MT-TiCN layer and an α-alumina layer which are formed by using a chemical vapor deposition method. A hard coating for cutting tools, which is a coating formed on a base material of a cutting tool formed of a hard material, the coating comprising: a TiCN layer; and an α-alumina layer formed on the TiCN layer, wherein: the α-alumina layer has a main peak (maximal strength peak) of (006) plane located between 20-40 degrees during a psi rocking analysis by an XRD; a residual stress in the α-Al 2 O 3 layer is −0.9-0.4 GPa; the TiCN layer is composed of TiC x N y O z (x+y+z≤1, x>0, y>0, z≥0); a composition ratio of C/(C+N) is greater than or equal to 0.4 and smaller than 0.5; the ratio of TC(220)/TC(422) is smaller than 0.45; and the ratio of TC(220)/TC(311) is less than 0.45.
1. A hard coating for cutting tools, which is a coating formed on a base material of a cutting tool formed of a hard material, the coating comprising:
a TiCN layer; and
an α-alumina layer formed on the TiCN layer, wherein:
the α-alumina layer has a main peak (maximal strength peak) of (006) plane located between 20-40 degrees during a psi rocking analysis by an XRD;
a residual stress in the α-Al 2 O 3 layer is −0.9-0.4 GPa;
the TiCN layer is composed of TiC x N y O z (x+y+z≤1, x>0, y>0, z≥0);
a composition ratio of C/(C+N) is greater than or equal to 0.4 and smaller than 0.5;
the ratio of TC(220)/TC(422) represented by Formula 1 is smaller than 0.45; and
the ratio of TC(220)/TC(311) is smaller than 0.45,
TC ( hkl )= I ( hkl )/ Io ( hkl ){1/ nΣI ( hkl )/ Io ( hkl )}−1, [Formula 1]
wherein:
I(hkl) is a (hkl) reflection strength;
Io(hkl) is a standard strength according to JCPDS card 42-1489;
n is the number of reflections used for calculation; and
(hkl) reflection uses (111), (200), (220), (311), (331), (420), (422) and (511)).
2. The hard coating for cutting tools of claim 1 , wherein a thickness of the TiCN layer is 7-10 μm.