Publications
32 results found
Kontis P, Yusof HAM, Pedrazzini S, et al., 2016, On the effect of boron on grain boundary character in a new polycrystalline superalloy, Acta Materialia, Vol: 103, Pages: 688-699, ISSN: 1359-6454
The role of boron in conferring the grain boundary character in a new polycrystalline superalloy suitable for power generation applications is considered. One boron-free and three boron-containing variants are studied using a suite of high resolution characterisation techniques including atom probe tomography (APT), high resolution secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The primary effect of boron addition is the suppression of Cr-rich M23C6 carbide and the formation instead of the Cr-rich M5B3 boride. The SIMS analysis indicates that the boride particles are distributed fairly uniformly along the grain boundaries, of length up to 500 nm along the grain boundary. The substantial majority of the boron added resides in the form of these M5B3 borides; some boron segregation is found at the γ′/M5B3 interfaces but interfaces of other forms – such as γ/γ′, γ/M5B3, γ/MC and γ′/MC – show no significant segregation. Creep testing indicates that the optimum boron content in this alloy is 0.05 at.%.
Segersall M, Kontis P, Pedrazzini S, et al., 2015, Thermal-mechanical fatigue behaviour of a new single crystal superalloy: effects of Si and Re alloying, Acta Materialia, Vol: 95, Pages: 456-467, ISSN: 1359-6454
The thermal–mechanical fatigue (TMF) behaviour of a new single crystal superalloy suitable for power generation applications is considered. Effects of alloying with either Si or Re are elucidated. Out-of-phase TMF is emphasised, although to clarify the effects arising some static creep deformation tests are also carried out. A significant Si-effect is found: a modest addition of 0.25 wt.% Si increases the TMF life by a factor of 2. A greater lower temperature yield stress and thinner slip bands traversing the γ′-phase – with a concomitant greater resistance to recrystallisation and cracking along them – contribute to the enhanced TMF performance promoted by Si alloying. Alloying with Re, whilst improving the creep behaviour more markedly than Si, does not have such a strong effect on TMF life. The results provide insights into the composition/performance relationships relevant to the TMF performance of single crystal superalloys.
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