Surface-coated cutting tool

Abstract

This invention provides a surface-coated cutting tool which exhibits excellent fracture resistance and wear resistance in high-speed cutting, such as high-speed gear cutting, high-speed milling, and high-speed drilling. The surface-coated cutting tool includes a hard coating layer composed of an alternately laminated layer structure of at least a thin layer A and a thin layer B formed on the surface of a tool substrate, such as a cemented carbide substrate, a cermet substrate, and a high-speed tool steel substrate. The thin layer A is an (Al, Cr, Si)N layer which satisfies a compositional formula: [Al X Cr Y Si Z ]N (0.2≦X≦0.45, 0.4≦Y≦0.75, 0.01≦Z≦0.2, and X+Y+Z=1 in terms of atomic ratio). The thin layer B is an (Al, Ti, Si)N layer which satisfies a compositional formula: [Al U Ti V Si W ]N (0.05≦U≦0.75, 0.15≦V≦0.94, 0.01≦W≦0.1, and U+V+W=1 in terms of atomic ratio).

The invention claimed is: 
     
       1. A surface-coated cutting tool comprising a hard coating layer formed on a surface of a tool substrate, the hard coating layer is composed of an alternately laminated layer structure of at least a thin layer A and a thin layer B, in which
 the thin layer A has a thickness of 0.01 to 0.1 μm, 
 the thin layer B has a thickness of 0.01 to 0.1 μm, and 
 a total thickness of the thin layers A and B is within 1 to 10 μm: 
 (a) the thin layer A is a complex nitride layer of Al, Cr and Si, and when expressing a composition of the complex nitride layer as a compositional formula [Al X Cr Y Si Z ]N, each X, Y and Z satisfies the relations,
   0.2≦X≦0.45, 0.4≦Y≦0.75, 0.01≦Z≦0.2, and X+Y+Z=1
 
 
 (where all of X, Y, and Z are atomic ratios); and 
 (b) the thin layer B is a complex nitride layer of Al, Ti, and Si, and when expressing a composition of the complex nitride layer as a compositional formula [Al U Ti V Si W ]N, each U, V and W satisfies the relations,
   0.05≦U≦0.75, 0.15≦V0.94, 0.01≦W≦0.1, and U+V+W=1
 
 
 (where all of U, V, and W are atomic ratios), 
 wherein the hard coating layer includes: 
 an upper layer composed of an alternately laminated layer structure of the thin layer A and the thin layer B, and 
 an under layer formed so as to be interposed between the upper layer and the surface of the tool substrate; and 
 the under layer has a composition which satisfies the compositional formula of the thin layer A or the thin layer B. 
 
     
     
       2. The surface-coated cutting tool according to  claim 1 , wherein
 the under layer has a thickness of 0.5 to 10 μm. 
 
     
     
       3. The surface-coated cutting tool according to  claim 1 , wherein its hard coating layer includes
 an upper layer composed of an alternately laminated layer structure of the thin layer A and the thin layer B, and   a under layer formed so as to be interposed between the upper layer and the surface of the tool substrate, and   the under layer has a thickness of 0.5 to 10 μm, and has a composition which satisfies the compositional formula of the thin layer B.   
     
     
       4. The surface-coated cutting tool according to  claim 1 , wherein the surface-coated cutting tool is a gear cutter in which its tool substrate is made of a high-speed tool steel. 
     
     
       5. The surface-coated cutting tool according to  claim 1 , wherein the surface-coated cutting tool is an end mill in which its tool substrate is made of a high-speed tool steel. 
     
     
       6. The surface-coated cutting tool according to  claim 1 , wherein the surface-coated cutting tool is an end mill or a drill in which its tool substrate is made of tungsten-carbide-based cemented carbide. 
     
     
       7. The surface-coated cutting tool according to  claim 2 , wherein the surface-coated cutting tool is a gear cutter in which its tool substrate is made of a high-speed tool steel. 
     
     
       8. The surface-coated cutting tool according to  claim 3 , wherein the surface-coated cutting tool is a gear cutter in which its tool substrate is made of a high-speed tool steel. 
     
     
       9. The surface-coated cutting tool according to  claim 2 , wherein the surface-coated cutting tool is an end mill in which its tool substrate is made of a high-speed tool steel. 
     
     
       10. The surface-coated cutting tool according to  claim 3 , wherein the surface-coated cutting tool is an end mill in which its tool substrate is made of a high-speed tool steel. 
     
     
       11. The surface-coated cutting tool according to  claim 2 , wherein the surface-coated cutting tool is an end mill or a drill in which its tool substrate is made of tungsten-carbide-based cemented carbide. 
     
     
       12. The surface-coated cutting tool according to  claim 3 , wherein the surface-coated cutting tool is an end mill or a drill in which its tool substrate is made of tungsten-carbide-based cemented carbide.