Measurement of the ductile-to-brittle transition temperature in a nickel aluminide coating by a miniaturised disc bending test technique
2003 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 165, no 1, 71-80 p.Article in journal (Refereed) Published
Nickel aluminide coatings are often employed to enhance the corrosion and oxidation resistance of nickel base gas turbine blades and vanes, as the high near-surface content of Al increases the ability to form an Al2O3 protective scale. The ductility of the coating depends on the type of aluminisation process and Ni-base material. In order to prevent coating degradation during service it is important to assess the ductile-to-brittle transition temperature (DBTT) in ductility of the coating. To determine the DBTT a miniaturised disc bending test (MDBT) technique is used, where a biaxial tensile stress is applied to a disc specimen. The DBTT of a NiAl coating, applied by a high-activity aluminium pack cementation process to a polycrystalline Ni-base superalloy (IN738 LC), was evaluated using the MDBT technique between room temperature (RT) and 860 degreesC. Test results gave a DBTT in biaxial ductility of the coating of approximately 760 degreesC. Above 760 degreesC, a significant increase in ductility was noted. Fractographic examination showed that the coating fractures in a mainly transgranular mode at RT but in a predominately intergranular mode at elevated temperatures, even at temperatures above DBTT.
Place, publisher, year, edition, pages
2003. Vol. 165, no 1, 71-80 p.
nickel aluminide, ductility, ductile-to-brittle transition temperature, miniaturised disc bending test, gas-turbine blades, small punch test, fracture-behavior, base superalloy, degradation
IdentifiersURN: urn:nbn:se:kth:diva-22158ISI: 000180293900009OAI: oai:DiVA.org:kth-22158DiVA: diva2:340856
QC 201005252010-08-102010-08-10Bibliographically approved