Superalloys 2021: Wednesday Part I - Blade Alloy Behavior
Program Organizers: Sammy Tin, University of Arizona; Christopher O'Brien, ATI Specialty Materials; Justin Clews, Pratt & Whitney; Jonathan Cormier, ENSMA - Institut Pprime - UPR CNRS 3346; Qiang Feng, University of Science and Technology Beijing; Mark Hardy, Rolls-Royce Plc; John Marcin, Collins Aerospace; Akane Suzuki, GE Aerospace Research
Wednesday 8:30 AM
September 15, 2021
Room: Live Session Room
Location: Virtual Event
Session Chair: Jonathan Cormier, ENSMA - Institut Pprime - UPR CNRS 3346; Jian Zhang, Institute of Metal Research
8:30 AM
Evidence of Short Range Order (SRO) by Dislocation Analysis in Single Crystal Ni-base Matrix Alloys with Varying Re Content after Creep: Florence Pettinari-Sturmel1; Joël Douin1; Fabian Krieg2; Ernst Fleischmann2; Uwe Glatzel2; 1CEMES - Université de Toulouse; 2Universität Bayreuth
TEM characterization of the deformation micromechanisms after interrupted creep test at 980 °C is proposed in the case of two single crystal Ni-based matrix alloys without rhenium (Re) and with 9 wt.% Re. This paper is aimed to propose an identification of the physical parameter at the origin of the strengthening effect of Re. The TEM observations carried out in the alloy with 9 wt.% Re indicate that the deformation proceeds through the propagation of long dislocation pile-ups. A leading pair is observed within these pile-ups. As this dislocation configuration is a signature of short-range-order (SRO), a quantitative approach is used to evaluate the SRO degree and thus the resistance due to SRO. The experimental positions of the dislocations are used to evaluate the total elastic force experienced by the dislocations. The strength associated with the SRO is evaluated to: 0 ≈ 50-60 mJ/m2. The observation of the matrix alloy without Re indicates the presence of both individual dislocations and some short dislocation pile-ups. It is also associated with a lower SRO degree. It can be concluded that the Re effect leads to an increase of the SRO degree. SRO is still present at high temperature (930°C) whereas it has been shown to disappear in similar matrix alloy with a lower amount of Re. Rhenium appears then to promote SRO. It can be at the origin of its well-known strengthening effect.
8:55 AM
Fretting Fatigue Life Extension for Single Crystal Ni-based Superalloy by Applying Optimized Surface Texturing: Masakazu Okazaki1; Rengaraj Balavenkatesh1; Satoshi Yamagishi2; Motoki Sakaguchi3; 1Nagaoka University of Technology; 2Niigata Institute of Technology; 3Tokyo Institute of Technology
Fretting fatigue (FF) lives of the CMSX-4 single crystal alloy have been measured, via some different counterpart materials in similar and dissimilar material combinations at room and elevated temperatures. The CMSX-4 specimens were machined so that the [001] crystallographic orientation was within 5°along the longitudinal axis of the SC specimen. In this work the work special attention was paid to find some useful methods to extend the FF lives by controlling the surface texture of contacting pad, as well as to get the metallurgical and mechanical aspects in the FF damage. The experimental works demonstrated that the texturing was effective to improve the FF lives. The stress field equations along the contacting interface have also been derived employing contact mechanics theories, so that the FF lives and the failure characteristics can be rationally estimated, on the basis of mechanical backgrounds. A new method proposed successfully provided reasonable predictions in agreement with the experimental results.
9:20 AM
Initiation of Fatigue Cracks in a Single Crystal Nickel Based Superalloy at Intermediate Temperature: Jian Zhang1; Y Huang2; D. Wang1; J Shen1; Y. Lu1; L. Lou1; 1Institute of Metal Research; 2Institute of Metal Research and University of Science and Technology of China
Fatigue tests under a series of stress amplitudes at 760 °C of a single crystal nickel based superalloy were conducted to investigate the relationships between loading conditions and initiation sites of fatigue cracks. It was found that initiation sites of the dominant fatigue crack gradually transferred from pores to MC carbides with an increase of the stress amplitude. At low stress amplitude, the fatigue crack that causes the final fracture initiated at pores and the fatigue life depended on size and shape of pores. Although the carbides on surface cracked as a result of oxidation and cyclic loading, the cracks did not penetrate the carbide/matrix interface. However, at high stress amplitude, the cracks in the carbide can penetrate the carbide/matrix interface rapidly under applied stress, and following crack propagation resulted in decisive fatigue fracture. Compared to blocky carbides on the surface, script carbides at subsurface were more likely to induce fatigue crack initiation.
9:45 AM Question and Answer Period