Abstract: Provided are a cutting insert and a cutting tool, capable of maintaining cutting performance for a long time. The cutting insert has a cutting blade made of a ceramic including the base and the cutting blade integrated with each other, wherein the base has a first coefficient of thermal expansion larger than a second coefficient of thermal expansion that the cutting blade has; and a difference between the first coefficient and the second coefficient is from more than 0 ppm/K to not more than 3 ppm/K.

Abstract: This invention provides a long-life Sialon insert, the cutting edge of which is resistant to wear and hard to fracture, and a cutting tool equipped with the Sialon insert. Provided are a Sialon insert made of a Sialon sintered body including a Sialon phase comprising an ?-Sialon and a ?-Sialon, and at least one element, originating from a sintering aid, selected from the group consisting of Sc, Y, Dy, Yb, and Lu in an amount of 0.5 to 5 mol % in terms of an oxide thereof, wherein an ?-value, which shows the proportion of the ?-Sialon in the Sialon phase, is from 10% to 40%; the ?-Sialon has a value of Z from 0.2 to 0.7 wherein Z is a variable of the formula Si6-ZAlZOZN8-Z and within a range: 0<Z?4.2; and the sintered body has an average thermal expansion coefficient of 3.5×10?6/K or less at temperatures of room temperature to 1000° C., and a thermal conductivity of 10 W/m·K or more at temperatures of room temperature to 1000° C., and a cutting tool comprising a holder equipped with the Sialon insert.

Abstract: A silicon nitride member, a method for manufacturing the silicon nitride member and a cutting tool are disclosed. A cutting tool 1 includes a substrate 3 formed through sintering of a silicon nitride material, and a hard film 5 composed of a plurality of hard-component layers. The cutting tool 1 is characterized in that: when the amount of a grain boundary phase as measured at a central portion (for example, the barycenter) of the substrate 3 is taken as 100% by volume, the amount of the grain boundary phase at a depth of 300 ?m from the surface of the substrate 3 is 50% to 70% by volume; when the strength of the substrate 3 as measured before coating with the hard film 5 is taken as 100%, the hardness as measured after coating with the hard film 5 is 70% to 95%; and a change in weight of the substrate 3 associated with sintering is 1.5% to 3.5% by weight.

Abstract: Sintered silicon nitride and a silicon nitride tool. The mean major axis length, the mean minor axis length, and the aspect ratio, represented by (mean major axis length/mean minor axis length) of constituent sintered silicon nitride grains in a silicon nitride tool are controlled, and the thermal conductivity and/or fracture toughness Kc thereof are enhanced, thereby providing a tool having a cutting edge which is not prone to chipping.

Abstract: Sintered silicon nitride containing silicon nitride substantially as a primary component and containing substantially no Al2O3. The sintered silicon nitride further contains at least one element selected from among a Group 4 element of the periodic table, a rare earth element and Mg. The amount of the selected element as converted to its oxide is at least 0.5 mol % and less than 2.6 mol % based on the entirety of the sintered silicon nitride. Also disclosed is a cutting tip, a wear-resistant member, a cutting tool and a method for producing the sintered silicon nitride.

Abstract: Sintered silicon nitride and a silicon nitride tool. The mean major axis length, the mean minor axis length, and the aspect ratio, represented by (mean major axis length/mean minor axis length) of constituent sintered silicon nitride grains in a silicon nitride tool are controlled, and the thermal conductivity and/or fracture toughness Kc thereof are enhanced, thereby providing a tool having a cutting edge which is not prone to chipping.

Abstract: A cermet tool 1 having a hard layer 11 which is very hard and which covers the surface of the tool 1, and an interior portion 13 which is covered with and softer than the hard layer 11. A nose 7, which comes into contact with a workpiece during cutting, is formed at a corner of the cermet tool 1. The tip of the nose 7 is radiused by honing to a curvature having a radius of 0.04 mm to 0.16 mm so as to form a radiused portion 15 where the interior portion 13 of the tool 1 is exposed. Accordingly, the hard layer 11 is disposed around the radiused portion (exposure portion) 15, and provides a cermet tool having excellent resistance to chipping and wear.

Abstract: A cermet tool that has excellent thermal crack resistance, while maintaining plastic deformation resistance, wear resistance and a long service life even when it is used for intermittent cutting is disclosed. The cermet tool comprises Ni or Ni and Co in a total amount of 4-20 wt. %, Ti in an amount of 50-60 wt. %, V, Cr, Zr, Nb, Mo, Hf, Ta, and W in a total amount of 30-40 wt. %, C in an amount of 5-10 wt. %, and N in an amount of 3-8 wt. %. The carbonitride phase contains grains of a Ti carbonitride phase containing Ti in an amount of 90 wt. % or more with respect to all the metal components of the phase. When the cross-sectional microcrystalline structure of the cermet is observed, the ratio of “total area of grains of the Ti carbonitride phase having a ratio of Dmax/Dmin of 1.5 or more” to “total area of the hard phase” is 50% or more.