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Title: Development of platinum alloys for high-temperature service
Author: Fairbank, G. B.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2003
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This dissertation describes the results of investigations carried out by the author into the alloying behaviour and high temperature mechanical properties of a number of binary and ternary systems based on Pt. The main focus of the investigation was to determine whether two-phase superalloy analogues based on Pt could be produced, and whether these alloys had any potential as a turbine material. An examination of the phase equilibria of the Pt-Hf and Pt-Zr systems (chosen due to the possibility of producing a two-phase f.c.c. – Ll2 (g-g’) alloy, analogous to the Ni-base superalloys) led to the discovery of a new compound, Pt8Hf, and confirmation of the existence of the compound Pt8Zr. The presence of these two phases eliminates the possibility of producing a superalloy analogue in either binary system. In addition to the above compounds, the existence of a non-stoichiometric Ll2 intermetallic (g’) was confirmed in both systems. The existing Pt-Zr binary phase diagram was modified on the basis of these results, and the Pt-Hf binary phase diagram was plotted for the first time. Formation of the low temperature phases Pt8Hf and Pt8Zr was suppressed by the addition of Rh, and in the Pt-Ph-Hf and Pt-Rh-Zr systems a g-g’ two-phase field was identified. Tentative isothermal sections of the ternary phase diagrams of both the Pt-Rh-Zr systems were suggested. In addition to these two systems, the Pt-Ti-Cr system was also investigated. It was found that the two g’ intermetallics Pt3Ti and Pt3Cr were likely to be connected, such that a g-g’ alloy could be produced in the Pt-Ti-Cr system. The high temperature mechanical properties of a Pt-Rh-Hf alloy and a Pt-Ti-Cr alloy were investigated. The Pt-Rh-Hf alloy consisted of g’ precipitates in a g matrix, whilst the Pt-Ti-Cr alloy tested was in the as-cast condition and contained dendrites of g’ (Pt3(Ti,Cr)) in a g matrix. The composition Pt - 8.5 at %Rh - 17 at %Hf was found to possess higher proof stress over the temperature range investigated (1000 °C - 1500 °C) than other known single-phase and two-phase Pt alloys. The Pt-Ti-Cr alloy had far lower proof stress than the Pt-Rh-Hf alloy over the same temperature range. The Pt-Rh-Hf alloy was also shown to have promising creep resistance, when compared to other Pt-based alloys designated for high temperature service.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available