Fatigue Behaviors of a NiCrAlYSi Coated Directionally Solidified Nickel Base Superalloy
| Periodical | Advanced Materials Research (Volumes 33 - 37) |
|---|---|
| Main Theme | Advances in Fracture and Materials Behavior |
| Edited by | Wei Yang, Mamtimin Geni, Tiejun Wang and Zhuo Zhuang |
| Pages | 229-236 |
| DOI | 10.4028/www.scientific.net/AMR.33-37.229 |
| Citation | Hui Chen Yu et al., 2008, Advanced Materials Research, 33-37, 229 |
| Online since | March, 2008 |
| Authors | Hui Chen Yu, Bin Zhong, Xue Ren Wu, Hui Ji Shi |
| Keywords | Directionally Solidified Nickel Base Superalloy, Fatigue Behaviour, NiCrAlYSi Coating |
| Price | US$ 28,- |
The fatigue behaviors of a directionally solidified (DS) nickel base superalloy, coated with a MCrAlY coating (NiCrAlYSi) were studied. Two kinds of tests were performed. One kind of tests are low cycle fatigue (LCF) test under strain control at different temperatures, another kind of tests are stress controlled LCF test with SEM-servo hydraulic testing machine for in situ cracking observation. The results show that the effect of coating on LCF life of coating/substrate system was rather different according to different strain levels and temperatures. The coating has no or less effect on LCF life under high strain range and the LCF life is governed by fatigue behavior of substrate in spite of the difference of temperature. However, when strain range is smaller, crack initiation and propagation are observably affected by temperature, which leads to a shorter LCF life of coating/substrate system at 500ºC and a longer LCF life at 760ºC or 980ºC. This means the failure of coating/substrate system is dominated by the cracking of surface coating under low strain range. The brittleness at 500ºC lower than DBTT results in rapid stage II crack propagation. The crack initiation from coating surface was in situ observed at room temperature and 700 ºC and it was found that cracks usually initiated from the surface roughness of coating and then propagate to failure. The brittleness and surface roughness are the basic acceptable causes leading to the early damage of a coating/substrate system.
