ISSN:
1662-8985
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The fatigue behaviors of a directionally solidified (DS) nickel base superalloy, coated witha MCrAlY coating (NiCrAlYSi) were studied. Two kinds of tests were performed. One kind of testsare low cycle fatigue (LCF) test under strain control at different temperatures, another kind of testsare stress controlled LCF test with SEM-servo hydraulic testing machine for in situ crackingobservation. The results show that the effect of coating on LCF life of coating/substrate system wasrather different according to different strain levels and temperatures. The coating has no or less effecton LCF life under high strain range and the LCF life is governed by fatigue behavior of substrate inspite of the difference of temperature. However, when strain range is smaller, crack initiation andpropagation are observably affected by temperature, which leads to a shorter LCF life ofcoating/substrate system at 500ºC and a longer LCF life at 760ºC or 980ºC. This means the failure ofcoating/substrate system is dominated by the cracking of surface coating under low strain range. Thebrittleness at 500ºC lower than DBTT results in rapid stage II crack propagation. The crack initiationfrom coating surface was in situ observed at room temperature and 700 ºC and it was found thatcracks usually initiated from the surface roughness of coating and then propagate to failure. Thebrittleness and surface roughness are the basic acceptable causes leading to the early damage of acoating/substrate system
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.229.pdf
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