Nissan Motor Company Limited

Hitachi Powdered Metals Co., Ltd.

Shinichi Umino

Akira Fujiki

Hiroyuki Ishikawa

Hiromasa Imazato

Tsutomu Uemura

Hiroshi Sugihara

The invention relates to a method of preparing a composite sintered body having inner and outer portions fitted with each other. The method includes the steps of: (a) preparing an inner powder compact; (b) preparing an outer powder compact; (c) fitting the inner and outer powder compacts with each other so as to prepare a composite powder compact; and (d) sintering the composite powder compact so as to prepare the composite sintered body. The inner and outer powder compacts are respectively selected such that, during the step (d), the amount of growth of the inner powder compact becomes greater than that of the outer powder compact. Each of the inner and outer composite powder compacts is made of one member selected from the group consisting of a wax-type segregation prevention powder mixture and a metal-soap-type segregation prevention powder mixture. At least one of the inner and outer composite powder compacts is made of the wax-type segregation prevention powder. According to the method, the mechanical property of each of the inner and outer portions of the composite sintered body is not limited, and the bonding strength between the inner and outer portions is substantially high.

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Kanagawa, Japan

Shinichi Umino