Influence of TiN coating on the rolling contact fatigue strength of mild steel
Sawamoto Akira; Nokubo Shunichi; Ide Yukio; Fujita Takeo; Fukui Takashi; Yasuoka Kazutoshi
Abstract:The surface of ring-like annealed mild steel specimens with diameter of 30 mm and thickness of 8 mm was coated with TiN film by an activated reactive evaporation (ARE) method. A pair of ring-like specimens contacted each other in the radius direction were set to the Nishihara type wear testing machine. They were rotated at the speed of 13.3 rev./s under the condition of applied stress of 330 to 1100 MPa and pure rolling contact with lubricant. The thin TiN film was uniformly produced on the surface of specimen by ARE method. This film adhered well to the surface of mild steel and it had enough bonding strength to mild steel even under pure rolling contact with lubricant. The annealed mild steel specimens coated with TiN had superior rolling contact fatigue strength than the uncoated ones. The fatigue life of the specimen coated with TiN was about eighteen times as large as that of the uncoated specimen under the same contact stress. TiN film on the surface of specimen was effective to suppress the generation of surface crack of specimens. The work hardening layer formed by repeated contact stress was near the surface of specimen and the degree of work hardening became larger with an increase in contact stress. Key Words:TiN coating, mild steel, rolling contact fatigue strength, crack, work hardening, bonding, wear