| Autor: |
Yuan, Kang, Peng, Ru Lin, Li, Xin Hai, Johansson, Sten |
| Zdroj: |
Applied Mechanics and Materials; December 2011, Vol. 148 Issue: 1 p24-29, 6p |
| Abstrakt: |
High-cycle-fatigue (HCF) fracture mechanism of nickel-based superalloy IN 792 coated with Pt-modified aluminide outward-diffusion coating is studied with focus on the influence of coating cracks. It is found that cracking of the diffusion coating prior to HCF tests has little influence on the fatigue limit of specimens with thin coating (50 μm) but lowers the fatigue limit of specimens with thick coating (70 μm). By fractographic analysis, three types of fractural modes are established according to their crack initiations: internal, external and mixed. While external fractural mode is related to the propagation of existing cracks in the coating, internal facture initiates often at Ti-Ta-W-rich carbides and/or topological-close-packed (TCP) phases and grainboundaries in the superalloy. Increasing the thickness of diffusion coating or the amplitude stress promotes the fractural mode transition from internal/mixed to external. The influence of precracking of coatings on the HCF fracture mechanism can be qualitatively explained by its influence on the stress intensity factor. |
| Databáze: |
Supplemental Index |
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