To provide an impeller bearing structure of a water pump having the long service life for restraining abrasion of a sliding surface, by preventing slurry abrasion even when sand having the particle size number of μ-20 μm is mixed in cooling water, by preventing the occurrence of cavitation erosion, and a highly reliable electric water pump using such a bearing structure.
Since an aluminum diffusion layer B2 of gradually reducing the concentration of aluminum as a distance from a surface increase, is formed between an alumina layer B1 and a metallic base material C by diffusing and permeating the aluminum in a metallic surface for constituting an outer peripheral surface of a shaft 27 and a sliding surface of sliding bearings 35 and 36, adhesive force between the alumina layer B1 and the metallic base material C is largely improved. The alumina layer B1 provided by a diffusion permeation method is high in surface hardness, and for example, a crack and a pore are less than a coating film by a thermal spraying method, and slurry abrasion and the cavitation erosion of the sliding surface can be effectively restrained.
Miyazaki Yoshio
Kaoru Onozuka
Akio Tagami
High Masahiro
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