Whisker reinforced ceramic cutting tool and composition thereof

A ceramic cutting tool comprising:

• a rake face;
• and a flank face, a cutting edge at the juncture of the rake face and the flank face;
• a ceramic composition having a matrix comprising at least 50 volume percent of one or more of the carbides, nitrides and carbonitrides of hafnium, molybdenum, zirconium, tantalum, niobium, vanadium, tungsten, titanium, and solid solutions thereof, the matrix further includes sintering aid residue present from the use of one or more sintering aids as a starting component in an amount less than 0.5 weight percent of the starting components wherein the sintering aid comprises one or more of yttria, magnesia and zirconia, wherein the matrix comprises between 60 and 99.8 volume percent of the ceramic composition;
• and
• ceramic whiskers uniformly dispersed throughout the matrix wherein the ceramic whiskers comprise between 0.2 and 40 volume percent of the ceramic composition.

A method of cutting metal wherein a ceramic cutting tool is brought into contact with a metal workpiece and the ceramic cutting tool and metal workpiece move relative to each other whereby metal is removed by the ceramic cutting tool from the metal workpiece using a ceramic cutting tool comprising:

• a rake face and a flank face wherein the rake face and the flank face intersect to form a cutting edge;
• the composition of the ceramic cutting tool comprising a matrix including:
• titanium carbonitride in an amount of about 50 volume percent or more of the matrix;
• alumina in an amount that is greater than about 40 volume percent of the matrix;
• and
• sintering aid residue present from the use of one or more sintering aids as a starting component in an amount less than 0.5 weight percent of the starting components wherein the sintering aid comprises one or more of yttria, magnesia and zirconia;
• the matrix comprising between 60 and 99.8 volume percent of the composition of the ceramic cutting tool;
• the composition of the ceramic cutting tool further comprising ceramic whiskers uniformly dispersed throughout the matrix, the ceramic whiskers comprising between 0.2 and 40 volume percent of the composition;
• the titanium carbonitride having the formula Ti(CxNy) wherein y is less than 0.9 and greater than or equal to 0.5, and x+y=1;
• and
• the ceramic cutting tool having a fracture toughness of greater than or equal to about 6.3 MPam½KIC and a hardness of greater than or equal to about 94.7 Rockwell A.

A coated ceramic cutting tool comprising:

• a substrate presenting a rake face and a flank face, a cutting edge at the juncture of the rake face and the flank face;
• the substrate having a composition comprising a matrix comprising at least 50 volume percent of one or more of the carbides, nitrides and carbonitrides of hafnium, molybdenum, zirconium, tantalum, niobium, vanadium, tungsten, titanium and solid solutions thereof, the matrix further comprising the sinter aid residue present from the use of one more sintering aids as a starting component in an amount less than 1 weight percent of the starting components wherein the sintering aid comprises one or more of yttria, magnesia, and zirconia, wherein the matrix comprises between 60 and 99.8 volume percent of the substrate composition;
• ceramic whiskers uniformly dispersed throughout the matrix wherein the ceramic whiskers comprises between 0.2 and 40 volume percent of the substrate composition;
• and
• a coating on at least a portion of the substrate.