SILICON NITRIDE SINTERED COMPACT

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PROBLEM TO BE SOLVED : To provide a silicon nitride sintered compact suitable for a rolling bearing member excellent in processability in addition to mechanical strengths, abrasion resistance, and rolling life characteristics comparable to or higher than these of a conventional silicon nitride sintered compact in which the dispersion state of an auxiliary agent component can be controlled even when forming the sintered compact using a silicon nitride powder raw material which is low in purity and price. SOLUTION : The silicon nitride sintered compact prepared by mixing a silicon nitride powder manufactured by the metal nitriding method and a sintering auxiliary agent, and sintering the mixture contains 2-5 mass% of a rare earth element as a sintering auxiliary agent component, 1-5 mass% of an Al element, and 0.5-5 mass% of at least one element selected from the group consisting of Ti, Zr, Hf, W, Mo, Ta, Nb, and Cr wherein the porosity is not greater than 1%, the maximum length of silicon nitride crystal particles composing the silicon nitride sintered compact is not greater than 40 μm, the segregated agglutinate part of the auxiliary agent component in a crystal structure of the silicon nitride sintered compact is not greater than 20 μm, the silicon nitride sintered compact contains 10-3, 500 ppm of Fe and 10-1, 000 ppm of Ca as impurities, the fracture toughness value of the silicon nitride sintered compact is not less than 6 MPa m1/2, the flexural strength is not less than 600 MPa, and the crush strength is not less than 150 N/mm2. COPYRIGHT : (C)2011, JPO&INPIT