Coated Cutting Tool Insert

Abstract

The present invention discloses a coated cutting tool insert particularly useful for dry and wet machining, preferably milling, in low and medium alloyed steels, stainless steels, with or without raw surface zones. The insert is characterized by a WC-TaC-NbC-Co cemented carbide with a W alloyed Co-binder phase and a coating including an innermost layer of TiC x N y O z with columnar grains and a top layer at least on the rake face of a smooth α-Al 2 O 3 .

1 . A cutting tool milling insert for machining of low and medium alloyed steels, stainless steels, with or without raw surfaces during wet or dry conditions comprising a cemented carbide body and a coating,
 wherein said cemented carbide body has a composition of 8.5-9.7 wt % Co, 1.00-1.45 wt % TaC, 0.10-0.50 wt % NbC, and balance WC, a coercivity in a range 11.7-13.3 kA/m, and a CW-ratio of 0.85-<1.00, and   wherein said insert is at least partly coated with a 4.1-6.9 μm thick coating including at least three layers of TiC x N y O z  of which one layer is adjacent to the cemented carbide and a blasted α-Al 2 O 3 -layer is an outer layer at least on a rake face, the TiC x N y O z  layers having a total thickness of 1.9-3.6 μm, the coating comprising:   a first TiC x N y O z  layer adjacent to the cemented carbide having a composition of x+y=1, x>=0,   a second TiC x N y O z  layer having a composition of x>0.4, y>0.4 and 0=<z<0.1,   a third TiC x N y O z  layer adjacent to the α-Al 2 O 3 -layer having a composition of x+y+z >=1 and z>0, and   the α-Al 2 O 3 -layer having a thickness of 1.8-3.6 μm with flattened grains on surfaces that have been subjected to a blasting treatment.   
   
   
       2 . A Cutting insert according to  claim 1 , wherein the cemented carbide has the composition 8.6-9.5 wt-% Co and 1.00-1.45 TaC and 0.10-0.50 NbC. 
   
   
       3 . A cutting tool insert according to  claim 1 , wherein the coating includes a 0.1-1 μm coloured top layer at the flank faces. 
   
   
       4 . A cutting tool insert according to  claim 3  wherein the coloured layer consists of TiN, TiCN, TiC, ZrN and/or HfN deposited by CVD- or PVD-technique, preferably CVD-technique. 
   
   
       5 . Method of making a cutting insert comprising a cemented carbide body and a coating by powder metallurgical technique, the method comprising:
 wet milling of powders forming hard constituents and binder phase;   compacting the milled mixture to bodies of desired shape and sizes and   wherein said cemented carbide body has a composition of 8.5-9.7 wt % Co, 1.00-1.45 wt % TaC, 0.10-0.50 wt % NbC, and balance WC, a coercivity in a range 11.7-13.3 kA/m, and a CW-ratio of 0.85-<1.00, and   wherein said body is at least partly coated with a 4.1-6.9 μm thick coating including at least three layers of TiC x N y O z  forming an inner coating with an α-Al 2 O 3 -layer as the outer layer at least on a rake face, the TiC x N y O z -layers have a total thickness of 1.9-3.6 μm, the coating comprising:   a first TiC x N y O z  layer adjacent to the cemented carbide having a composition of x+y=1, x>=0, using a CVD method using a reaction mixture consisting of TiCl 4 , H 2  and N 2 ,   a second TiC x N y O z  layer having a composition of x>0.4, y>0.4 and 0=<z<0.1, by using a MTCVD-technique, temperature 885-850° C. and CH 3 CN as the carbon/nitrogen source,   a third TiC x N y Oz layer adjacent to the α-Al 2 O 3 -layer having a composition of x+y+z>=1 and z>0, using a CVD method using a reaction mixture consisting of TiCl 4 , H 2  and N 2 ,   wherein the α-Al 2 O 3 -layer with a thickness of 1.8-3.6 μm is deposited by using a CVD-technique, and   wherein the method includes subjecting the insert to a blasting treatment at least on the rake face.   
   
   
       6 . Method according to  claim 5 , wherein the method includes depositing an additional 0.1-1 μm coloured layer on top of the α-Al 2 O 3 -layer prior to the blasting treatment. 
   
   
       7 . Method according to  claim 5 , wherein the method includes depositing after the blasting treatment an additional 0.1-1 μm coloured top layer at the flank faces. 
   
   
       8 . Method of wet and dry milling of low and medium alloyed steels and stainless steels, with raw surfaces or pre-machined surfaces under stable conditions at cutting speeds and feed rates according to the following:
 milling with 90° entering angle at a cutting speed of 25-400 m/min, or   face milling at 45-75° entering angle at cutting speed of 25-400 m/min, or   high feed and round insert milling applications at cutting speed of 25-500 m/min and feed rate: 0.30-3.0 mm/tooth,   wherein an insert for any of the applications of milling, face milling and high feed and round insert milling is the insert according to  claim 1 .   
   
   
       9 . A cutting tool insert according to  claim 1 , wherein the composition includes 8.6-9.8 wt % Co. 
   
   
       10 . A cutting tool insert according to  claim 1 , wherein the composition includes 1.18-1.28 wt % TaC. 
   
   
       11 . A cutting tool insert according to  claim 1 , wherein the composition includes 0.25-0.35 wt % NbC. 
   
   
       12 . A cutting tool insert according to  claim 1 , wherein the coercivity is in the range 12.1-12.9 kA/m. 
   
   
       13 . A cutting tool insert according to  claim 1 , wherein the CW-ratio is 0.86-0.95. 
   
   
       14 . A cutting tool insert according to  claim 1 , wherein the composition of the first TiC x N y O z  layer adjacent to the cemented carbide has x<0.2 and z=0. 
   
   
       15 . A cutting tool insert according to  claim 1 , wherein the composition of the second TiC x N y O z  layer has z=0. 
   
   
       16 . A cutting tool insert according to  claim 1 , wherein the composition of the third TiC x N y O z  layer adjacent to the α-Al 2 O 3 -layer has z>0.2, x+y+z=1 and y<0.2. 
   
   
       17 . Method according to  claim 5 , wherein the composition includes 8.6-9.8 wt % Co. 
   
   
       18 . Method according to  claim 5 , wherein the composition includes 1.18-1.28 wt % TaC. 
   
   
       19 . Method according to  claim 5 , wherein the composition includes 0.25-0.35 wt % NbC. 
   
   
       20 . Method according to  claim 5 , wherein the coercivity is within 12.1-12.9 kA/m. 
   
   
       21 . Method according to  claim 5 , wherein the CW-ratio 0.86-0.95. 
   
   
       22 . Method according to  claim 5 , wherein the composition of the first TiC x N y O z  layer adjacent to the cemented carbide has x<0.2 and z=0. 
   
   
       23 . Method according to  claim 5 , wherein the composition of the second TiC x N y O z  layer has z=0. 
   
   
       24 . Method according to  claim 5 , wherein the composition of the third TiC x N y O z  layer adjacent to the α-A 2 O 3 -layer has z>0.2, x+y+z=1 and y<0.2. 
   
   
       25 . Method according to  claim 6 , wherein the coloured layer includes TiN, TiCN, TiC, ZrN or HfN. 
   
   
       26 . Method according to  claim 7 , wherein the coloured top layer includes TiN, TiCN, TiC, ZrN or HfN. 
   
   
       27 . Method according to  claim 8 , wherein the cutting speed for milling is 150-300 m/min. 
   
   
       28  Method according to  claim 8 , wherein the cutting speed for face milling is 150-300 m/min. 
   
   
       29 . Method according to  claim 8 , wherein the cutting speed for high feed and round insert milling applications is 150-400 m/min and the feed rate for high feed and round insert milling applications is 0.3-1.8 mm/tooth.