Sialon sintered body and cutting insert
A sialon sintered body and a cutting insert each having thermal shock resistance and VB wear resistance. The sialon sintered body and the cutting insert contain β-sialon and 21R-sialon and exhibit an X-ray diffraction peak intensity ratio [(I 21R /I A )×100] of 5% or greater and smaller than 30%, wherein I A represents the sum of the peak intensities of the sialon species, and I 21R represents the peak intensity of 21R-sialon, the ratio being calculated from the peak intensities of the sialon species obtained by using X-ray diffractometry.
1. A sialon sintered body containing β-sialon and 21R-sialon, characterized in that the sialon sintered body exhibits an X-ray diffraction peak intensity ratio [(I 21R /I A )×100] of 5% or greater and smaller than 30%, wherein I A represents the sum of the peak intensities of the sialon species, and I 21R represents the peak intensity of 21R-sialon, the ratio being calculated from the peak intensities of the sialon species obtained by using X-ray diffractometry; the sialon sintered body has a thermal expansion coefficient of 4.2 ppm/K or less in a range of room temperature to 600° C.; and
β-sialon represented by Si 6-Z Al Z O Z N 8-Z has a Z value of 0.3 to 1.0.
2. A sialon sintered body according to claim 1 , wherein
the sintered body contains at least one rare earth element B selected from the group consisting of La and Ce, and at least one rare earth element C selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Er, Yb, and Lu;
the mole ratio of rare earth element B to rare earth element C as oxides, M B :M C , is 1.0:0.06 to 1.0:5.0; and
the sialon sintered body contains the rare earth element B and the rare earth element C in a total amount, as oxides, of 0.8 mol % to 4.0 mol %.
3. A sialon sintered body according to claim 1 , which exhibits an X-ray diffraction peak intensity ratio [(I α /I A )×100] of 0% to 25%, wherein I A represents the sum of the peak intensities of the sialon species, and I α represents the peak intensity of α-sialon, the peak intensities of the sialon species being obtained by using X-ray diffractometry.
4. A sialon sintered body according to claim 3 , wherein
in α-sialon represented by M x (Si,Al) 12 (O,N) 16 (0<x≤2), M represents metallic elements including the rare earth element B selected from the group consisting of La and Ce and the rare earth element C selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Er, Yb, and Lu;
the sialon sintered body has a ratio A α /A S of 70% or smaller, wherein A S represents the atomic ratio of rare earth element B to rare earth element C, and A α represents the atomic ratio of rare earth element B to rare earth element C in α-sialon; and
the sialon sintered body exhibits an x-ray diffraction peak intensity ratio [(I α /I a )×100] of 3% to 25%.
5. A sialon sintered body according to claim 1 , wherein
the sialon sintered body contains 21R-sialon, and at least one of 12H-sialon and 15R-sialon among polysialon species including 21R-sialon, 12H-sialon, and 15R-sialon, and
the sialon sintered body exhibits an X-ray diffraction peak intensity ratio [(I p /I A )×100] of 50% or smaller, wherein I A represents the sum of the peak intensities of the sialon species, the peak intensities of the sialon species being obtained by using X-ray diffractometry, and I p represents the sum of the peak intensities of poly-type sialon species, the peak intensities of the poly-sialon species being obtained by using X-ray diffractometry.
6. A cutting insert formed of a sialon sintered body as recited in claim 1 .