On the Rapid Assessment of Mechanical Behavior of a Prototype Nickel-Based Superalloy using Small-Scale Testing
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On the Rapid Assessment of Mechanical Behavior of a Prototype Nickel-Based Superalloy using Small-Scale Testing SABIN SULZER, ENRIQUE ALABORT, ANDRE´ NE´METH, BRYAN ROEBUCK, and ROGER REED An electro-thermal mechanical testing (ETMT) system is used to assess the mechanical behavior of a prototype single-crystal superalloy suitable for industrial gas turbine applications. Miniaturized testpieces of a few mm2 cross section are used, allowing relatively small volumes to be tested. Novel methods involving temperature ramping and stress relaxation are employed, with the quantitative data measured and then compared to conventional methods. Advantages and limitations of the ETMT system are identified; particularly for the rapid assessment of prototype alloys prior to scale-up to pilot-scale quantities, it is concluded that some significant benefits emerge. https://doi.org/10.1007/s11661-018-4673-5 Ó The Author(s) 2018
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INTRODUCTION
NEW alloy grades are never deployed without careful testing of their properties and performance under conditions close to those experienced in service. Such so-called qualification activities can be difficult and costly; this explains why the time needed to insert them into new applications can be notoriously long.[1–3] Furthermore, processing costs for the production of pilot-scale material quantities can be excessively large—often too great to justify—thus leading to conservatism and undue emphasis on maintaining the status quo. Without a doubt, such challenges lead to a slackening in the pace of technological change. Consider, for example, the assessment of the mechanical response of a material destined for high-temperature applications. The yield stress depends upon temperature, but also on the strain rate. The creep resistance depends upon temperature once again, but also on the stress level. Even before the cyclic loading needed to assess fatigue behavior or the effects of a biaxial or triaxial stress state are considered, the number of SABIN SULZER and ANDRE´ NE´METH are with the Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK. Contact e-mail: [email protected] ENRIQUE ALABORT is with the Department of Engineering Science, University of Oxford. BRYAN ROEBUCK is with the National Physical Laboratory, Hampton Road, Teddington TW1 0LW, UK. ROGER REED is with Department of Materials, University of Oxford and also with the Department of Engineering Science, University of Oxford. Manuscript submitted January 18, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
conditions for which mechanical tests are needed can quickly become very significant. The difficulties identified above are then exacerbated. Moreover, there is a traditional emphasis—even today—on the use of standard testpieces of traditional design, which can mean that substantial volumes of material are needed. Might there be better ways of approaching this problem? The research reported in this paper was carried out with these ideas in mind. Miniaturized testpieces are used within a novel elec
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