SiAION material and cutting tools made thereof

Abstract

A SiAlON-based ceramic particularly suited for use as a cutting tool in the high speed chip forming machining of metals composed of a SiAlON matrix including a) a phase of alpha′ SiAlON represented by the general formula of M x (Si,Al) 12 (O,N) 16 , wherein 0<x<2 and M is at least two cationic elements, a first cationic element being 0.2 to 4 weight percent Mg and optionally between 0.5 and 15 weight percent of one or more of Ca, Sr, and Ba calculated as oxide, based on the SiAlON matrix, and a second cationic element being one or more of Y, Sc, La and the rare earth (RE) elements; b) a phase consisting of beta′ SiAlON represented by the general formula Si 6-z Al z O z N 8-z wherein 0<z<4.2; and c) a component containing glass, and at least one additional intergranular crystal phase that is detectable using X-ray diffraction techniques is provided.

1 . A SiAlON ceramic material having a SiAlON matrix comprising: 
 a) a phase of alpha′ SiAlON represented by the general formula of M x (Si,Al) 12 (O,N) 16 , wherein 0<x<2 and M is at least two cationic elements, a first cationic element being Mg and optionally one or more of Ca, Sr, and Ba, and a second cationic element being one or more of Y, Sc, La and the rare earth (RE) elements;    b) a phase of beta′ SiAlON represented by the general formula Si 6-z Al z O z N 8-z  wherein 0<z<4.2; and    c) a component containing glass, and at least one additional intergranular crystal phase that is detectable using X-ray diffraction (XRD) techniques,    wherein the amount of the first cationic element is 0.2 to 4 weight percent, calculated as an element and based on the SiAlON matrix, and the amount of the second cationic element is 0.5 to 15 weight percent, calculated as an oxide, based on the SiAlON matrix.    
     
     
         2 . The material of  claim 1 , wherein M is distributed between the alpha′ SiAlON phase and the component c).  
     
     
         3 . The material of  claim 2 , wherein the first cationic element is Mg alone.  
     
     
         4 . The material of  claim 1 , wherein the second cationic element is one or more of Sc, Y, La, Yb, Sm, Nd, Pr.  
     
     
         5 . The material of  claim 3 , wherein the second cationic element is one or both of Y and Yb.  
     
     
         6 . The material of  claim 3 , wherein the second cationic element is Y.  
     
     
         7 . The material of  claim 6 , wherein x is between 0.25 and 2, and wherein z is between 0 and 2, and wherein the weight ratio of a) to b) is between 1:99 and 99:1.  
     
     
         8 . The material of  claim 7 , wherein z is between 0 and 1, and wherein the weight ratio of a) to b) is between 20:80 and 80:20.  
     
     
         9 . The material of  claim 7 , wherein z is between 0 and 0.5, and wherein the weight ratio of a) to b) is between 35:65 and 65:35.  
     
     
         10 . The material of  claim 8 , wherein the amount of Mg is between 0.2 and 4 weight percent.  
     
     
         11 . The material of  claim 8 , wherein the amount of Mg is between 0.3 and 3 weight percent.  
     
     
         12 . The material of  claim 6 , wherein the amount of Mg is between 0.4 and 2.5 weight percent.  
     
     
         13 . The material of  claim 11 , wherein the second cationic element is included as yttrium oxide in an amount between 3 and 10 weight percent.  
     
     
         14 . The material of  claim 12 , wherein the second cationic element is included as yttrium oxide in an amount between 4 and 8 weight percent.  
     
     
         15 . The material of  claim 14 , having a hardness greater than 93.5 Rockwell A, and a fracture toughness greater than 6.5 MPam 1/2 .  
     
     
         16 . The material of  claim 15 , having a fracture toughness greater than 7.0 MPam 1/2 .  
     
     
         17 . The material of  claim 12 , which further comprises one or more substantially inert filler selected from a known oxide, nitride, silicide, carbide, carbo-oxy-nitride, oxy-carbide, carbo-nitride, or boride of one or more of the elements Ti, Zr, Hf, Nb, Ta, V, Cr, Mo, W, B, and Si, included in an amount between 1.5 and 40 volume percent, based on the ceramic material.  
     
     
         18 . The material of  claim 17 , wherein the filler is selected from one or more of TiN, Ti(C,N), Mo 2 C, TiC, and SiC, included in an amount between 2 and 25 volume percent.  
     
     
         19 . The material of  claim 18 , wherein the filler is selected from one or more of TiN, Ti(C,N), Mo 2 C.  
     
     
         20 . The material of  claim 19 , having a hardness greater than 92 Rockwell A, a fracture toughness greater than 6.5 MPam 1/2 .  
     
     
         21 . The material of  claim 20 , having a fracture toughness greater than 7.0 MPam 1/2 .  
     
     
         22 . The material of  claim 6 ,  15 ,  18  or  20 , in the form of a metal cutting tool insert.  
     
     
         23 . The material of  claim 6 ,  15 ,  18  or  20 , in the form of a ceramic tool for high speed chip forming of metallic materials, said ceramic tool comprising: a rake face over which chips formed during said chip forming machining will flow; a flank face; a cutting edge for cutting into said metallic materials at high speeds to form said chips formed at a junction of said rake face and said flank face.  
     
     
         24 . The material of  claim 6 ,  15 ,  18  or  20 , in the form of a metal cutting tool insert and optionally having a coating of a hard refractory material on at least part of its surface.  
     
     
         25 . The material of  claim 6 ,  15 ,  18  or  20 , in the form of a metal cutting tool insert and optionally having a partial or complete coating of a hard refractory material on at least part of its surface, said refractory material being selected from carbon, alumina, cubic boron nitride, titanium nitride, titanium carbo-nitride, and titanium aluminum nitride.