Mechanical properties and temperature dependence of an air plasma-sprayed NiCoCrAlY bondcoat
2006 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 200, no 8, 2695-2703 p.Article in journal (Refereed) Published
The elastic and inelastic properties were investigated for an air plasma-sprayed bondcoat (Ni-23Co-17Cr-12Al-0.5Y) at temperatures up to 800 degrees C. The yield strength was evaluated by using a miniaturised disc-bending test while the stress-strain behaviour and elastic modulus were determined through spherical indentation. The material was tested in both as-coated and heat-treated conditions (1500 h, 1000 degrees C). From the disc-bending tests it was observed that both conditions were macroscopically brittle both at low and high temperatures, with slow and stable crack propagation in the inter-splat region. Between room temperature and 500 degrees C the yield strength is constant and yield occurs by inter-splat shearing, but above this temperature the yield strength decreases due to yielding of the splats. This behaviour was confirmed by the fractographical examination that showed an inter-splat fracture surface at room temperature with small amount of plastic features, but at 800 degrees C a more dimpled and ruptured fracture appeared. Small difference in yield strength was found between the two conditions, and they had similar temperature dependence. However, their indentation stress-strain response was different, where the heat-treated condition had the largest resistance against inelastic deformation. The value of the elastic modulus was for the as-coated condition 137 GPa at 25 degrees C and 127 GPa at 800 degrees C, and for the heat-treated condition 226 GPa at 25 degrees C and 192 GPa at 800 degrees C, the difference between the two conditions being a result of internal oxidation.
Place, publisher, year, edition, pages
2006. Vol. 200, no 8, 2695-2703 p.
cavity expansion model, spherical indentation, miniaturised disc-bending test, mechanical properties, thermal barrier coatings, thermal barrier coatings, spherical indentation, ceramic coatings, elastic-modulus, fracture, microstructure, behavior, tests
IdentifiersURN: urn:nbn:se:kth:diva-15415DOI: 10.1016/j.surfcoat.2005.05.035ISI: 000235202100014ScopusID: 2-s2.0-30544433325OAI: oai:DiVA.org:kth-15415DiVA: diva2:333456
QC 201005252010-08-052010-08-05Bibliographically approved