Ngk Spark Plug Company, Limited

Hiroshi Yonekura

Takeshi Mitsuoka

Yusuke Katsu

Yoshito Kojima

Provided is a ceramic sintered body having high wear resistance and chipping resistance. Also provided are an insert, a cutting tool and a friction stir welding tool, each of which uses such a high-performance ceramic sintered body. The ceramic sintered body includes AlO(alumina), WC (tungsten carbide) and ZrO(zirconia), wherein Zr (zirconium) element is present at either one or both of: (1) a grain boundary between crystal grains of the AlO; and (2) a grain boundary of crystal grains of the AlO and crystal grains of the WC, wherein the ceramic sintered body contains 55.0 to 97.5 vol % of the WC, 0.1 to 18.0 vol % of the ZrO, and the balance being the AlO, and wherein the ZrOis in a phase of tetragonal structure (T) or a mixed phase of tetragonal structure (T) and monoclinic structure (M).

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Nagoya, Japan

Hiroshi Yonekura