| (Graded)(Ti,Al)N coatings with excellent wear resistance and extreme oxidation and corrosion properties were deposited on 1Cr11Ni2W2MoV stainless steel by arc ion plating. The influences of structures and residual stresses of the (graded) (Ti,Al)N coatings on the fatigue properties of the bulk material in room and high temperature were studied and the mechanisms were discussed..The (graded) (Ti,Al)N coatings were flat and compact observed by SEM,with B1NaCl structure identified by XRD. The depth distributions of the residual stresses in (graded) (Ti, Al) N coatings deposited on the steel were measured by the Stripping Layer Substrate Curvature Technique. The results show that the residual stresses in the coatings were compressive, which increased gradually from the coating/substrate interface and reach a maximum value at the middle region, then decreased until the surface. The residual stress level in the graded (Ti, Al)N near the interface was similar to that of TiN and much lower than that in Ti50Al50N. Furthermore the average stress in TiN was the lowest, and the average stress in the graded (Ti,Al)N coating was larger when the film was thicker.Rotary bending fatigue test was adopted for predicting high-cycles fatigue properties of the (graded) (Ti, Al) N coated and bulk steel. The S-N curves and the fatigue limits were tested, and the fracture appearances were observed. At room temperature, the fatigue strength of Ti70Al30N and graded (Ti,Al)N coated samples were 571.0MPa and 575.0MPa respectively, increased evidently than that of the bulk steel, whose fatigue strength was 533.0MPa.However, at 500oC, fatigue strength of graded (Ti,Al)N ,Ti70Al30N coated and bulk steel were 450.0MPa,494.0 MPa and 454.0MPa respectively.But the fatigue life of the bulk steel was improved by the graded coating at higher stress level. Main reason may lie in the initiation and expansion of the fatigue crack is retarded by the residual compressive stress in Ti70Al30N and graded (Ti,Al)N coatings.
|
PDF Full Text Request