Coated grooving or parting insert

Abstract

The present invention relates to a coated cutting tool insert useful for grooving or severing steel components such as steel or stainless steel tubes and bars. The insert is characterized by WC—Co-based cemented carbide substrate having a highly W-alloyed Co-binder phase and a relatively thin coating including an inner layer of TiC x N y O z with columnar grains followed by a layer of fine grained κ—Al 2 O 3 and a top layer of TiN.

1. A cutting tool insert comprising:
 a cemented carbide body comprising 
 6-15 weight % Co, 0.2-1.8 weight % cubic carbides of Ti, Ta, Nb or any combination thereof, a highly W-alloyed binder phase with a CW-ratio of 0.78-0.93, and the balance WC; and  
 
 a coating comprising 
 a first innermost layer of TiC x N y O z  wherein x+y+z=1, the first layer having a thickness of 0.1-1.5 μm and equiaxed grains with size <0.5 μm,  
 a second layer of TiC x N y O z  wherein x+y+z=1, the second layer having a thickness of 0.4-3.9 μm, with columnar grains with an average diameter of 0.1-5.0 μm,  
 a third layer of a smooth fine-grained κ—Al 2 O 3  layer with a thickness of 0.5-5.5 μm, and  
 a total thickness of the first innermost TiC x N y O z  and the second TiC x N y O z  layer is 0.5-4.0 μm, and the total thickness of all layers is 2.0-6.0 μm.  
 
 
     
     
       2. The cutting tool insert of  claim 1 , wherein the body comprises 9-12 weight % Co and a CW ratio of 0.80-0.91. 
     
     
       3. The cutting tool inset of  claim 1 , wherein in the first layer y>x and z<0.2, and the thickness of the first layer is 0.1-0.6 μm. 
     
     
       4. The cutting tool insert of  claim 1 , wherein in the second layer z=0, x>0.3 and y>0.3, the second layer has a thickness of 1.5-3.0 μm, with the columnar grains having an average diameter of 0.1-2.0 μm. 
     
     
       5. The cutting tool insert of  claim 1 , wherein in the third layer the grains of the κ—Al 2 O 3  have a size on the order of 0.5-2.0 μm, and the third layer has a thickness of 0.5-3.0 μm. 
     
     
       6. The cutting tool insert of  claim 1 , wherein the total thickness of the first and second layers is 1.5-3.5 μm. 
     
     
       7. The cutting tool insert of  claim 1 , wherein the total thickness of all the layers is 3.0-5.0 μm. 
     
     
       8. The cutting insert of  claim 1  further comprising an outermost layer of TiN having a thickness of 0.1-1.0 μm. 
     
     
       9. The cutting insert of  claim 8 , wherein the outermost TiN-layer has been removed along the cutting edge. 
     
     
       10. A method of making a cutting tool insert comprising a WC—Co-based cemented carbide body with a highly W-alloyed binder phase and a CW-ratio of 0.78-0.93, the method comprising coating the body by the steps of:
 forming a first innermost layer of TiC x N y O z  with a CVD-based technique, wherein x+y+z=1, the first layer having a thickness of 0.1-1.5 μm and equiaxed grains with a size <0.5 μm,  
 forming a second layer of TiC x N y O z  by a MTCVD-technique, wherein x+y+z=1, the second layer having a thickness of 0.4-3.9 μm and columnar grains with an average diameter of 0.1-5.0 μm,  
 forming a third layer of a smooth κ-Al 2 O 3  having a thickness of 0.5-5.5 μm, and  
 forming the layers such that the total thickness of the first and second layers is 0.5-4.0 μm, and the total thickness of all layers is 2.0-6.0 μm.  
 
     
     
       11. The method of  claim 10 , wherein the step of forming the first layer further comprises providing the first layer with y>x and z<0.2 and a thickness of 0.1-0.6 μm. 
     
     
       12. The method of  claim 10  wherein the step of forming the second layer further comprises using acetonitrile as the carbon and nitrogen source and forming the second layer at a temperature of 850-900° C., the step of forming the second layer further comprises providing z=0, x>0.3 and y>0.3, a thickness of 1.5-3.0 μm, and with the columnar grains having an average diameter of 0.1-2.0 μm. 
     
     
       13. The method of  claim 10 , wherein the third layer is provided with a thickness of 0.5-3.0 μm. 
     
     
       14. The method of  claim 10 , wherein the method further comprises forming an outer layer of TiN having a thickness of <1 μm. 
     
     
       15. The method of  claim 10 , wherein the method further comprises providing the first and second layers with a total thickness of 1.5-3.5 μm, and a total thickness of all layers of 3.0-5.0 μm. 
     
     
       16. The method of  claim 10  wherein the said cemented carbide body has a cobalt content of 9-12 weight % and 0.4-1.8 weight % cubic carbides of Ta and Nb. 
     
     
       17. The method of  claim 10  wherein the cemented carbide body has a cobalt content of 10-11 weight %. 
     
     
       18. The method of  claim 17  wherein the cemented carbide body has a CW-ratio of 0.82-0.90. 
     
     
       19. The method of  claim 14 , wherein the outermost TiN-layer is removed along a cutting edge. 
     
     
       20. The method of  claim 19 , wherein the outermost TiN-layer is removed by brushing. 
     
     
       21. The cutting tool inset of  claim 3 , wherein in the second layer z= 0 , x> 0 . 3  and y> 0 . 3 , the second layer has a thickness of  1 . 5 - 3 . 0  μm with the columnar grains having an average diameter of  0 . 1 - 2 . 0  μm. 
     
     
       22. The cutting tool insert of  claim 21 , wherein in the third layer the grains of the κ-Al 2   O   3    have a size on the order of  0 . 5 - 2 . 0  μm and the third layer has a thickness of  0 . 5 - 3 . 0  μm.   
     
     
       23. The cutting tool insert of  claim 22 , wherein the total thickness of all the layers is  3 . 0 - 5 . 0  μm. 
     
     
       24. The cutting insert of  claim 22  further comprising an outermost layer of TiN having a thickness of  0 . 1 - 1 . 0  μm. 
     
     
       25. The cutting insert of  claim 24 , wherein the outermost TiN-layer has been removed along the cutting edge. 
     
     
       26. The method of  claim 11  wherein the step of forming the second layer further comprises using acetonitrile as the carbon and nitrogen source and forming the second layer at a temperature of  850 - 900 ° C., the step of forming the second layer further comprises providing z= 0 , x> 0 . 3  and y> 0 . 3 , a thickness of  1 . 5 - 3 . 0  μm and with the columnar grains having an average diameter of  0 . 1 - 2 . 0  μm. 
     
     
       27. The method of  claim 26 , wherein the method further comprises forming an outer layer of TiN having a thickness of < 1  μm. 
     
     
       28. The method of  claim 27 , wherein the outermost TiN-layer is removed along a cutting edge. 
     
     
       29. The method of  claim 26 , wherein the method further comprises providing the first and second layers with a total thickness of  1 . 5 - 3 . 5  μm and a total thickness of all layers of  3 . 0 - 5 . 0  μm. 
     
     
       30. The method of  claim 10  wherein the said cemented carbide body has a cobalt content of  9 - 12  weight % and  0 . 4 - 1 . 8  weight % cubic carbides of Ta and Nb. 
     
     
       31. The method of  claim 30  wherein the cemented carbide body has a CW-ratio of  0 . 82 - 0 . 90 .