| 摘要 |
PROBLEM TO BE SOLVED: To secure corrosion resistance, and improve abrasion resistance and cavitation resistance by forming a hardening layer composed of titanium nitride or chrome nitride on the surface of a trochoidal gear to constitute the main part of a solution pump using an ammonia solution as a working fluid. SOLUTION: An inner gear 11 and an outer gear 10 contact with each other through a titanium nitride film formed on respective surfaces, and an inner gear 23 and an outer gear 22 contact with each other through a titanium nitride film formed on respective surfaces. In these inner gears and outer gears, since the gear inside is protected by the titanium nitride film which has high hardness and is not chemically corroded by an ammonia aqueous solution, shape accuracy and surface roughness in a gear surface of the gears are maintained, and surface hardness is enhanced. Since the titanium nitride film is formed by being coated with titanium nitride, adhesion with a gear surface base material is strong, and it is hardly separated.
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