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Title: Oxidation of nickel-base superalloys for turbine disc and advanced turbine blade applications
Author: Chen, J.-H.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1996
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Isothermal and cyclic oxidation tests were carried on three "chromia" forming superalloys, Astroloy, Udimet 720 and Waspaloy used as turbine disc materials, and two advanced single crystal superalloys, CMSX4 and RR3000, developed as turbine blade materials, with and without Pt-aluminide coatings. For the turbine disc materials, external chromia scales were formed to protect the alloy substrate and also some internal oxidation developed. The oxidation behaviour was mainly related to the contents of aluminium, chromium and titanium and also the microstructure. For "alumina" forming superalloys without coatings, both CMSX4 and RR3000 formed a continuous alumina subscale after a period of transition oxidation at temperatures above 1000oC in isothermal tests. However the two alloys cannot form an alumina scale at 900oC and thus the growth rate of scale at 900oC was higher than at higher temperatures. The reduction of sulphur content to less than 1 ppm in CMSX4 was shown to improve the scale adhesion in the cyclic tests. For the Pt-aluminide coated CMSX4 and RR3000 excellent oxidation resistance was revealed in both isothermal and cyclic tests at 1100oC due to the formation of adherent alumina scale on the surface. As a result, the oxidation behaviour was very similar between the isothermal and cyclic tests. A deleterious effect was found in the interdiffusion zone of the Pt-aluminide coated alloys due to void and microcrack formation. This was attributed to the inward diffusion of platinum which caused the formation of needle-like TCP phases due to the high contents of rhenium in the two alloys.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available