Materials for High Temperature Applications: Next Generation Superalloys and Beyond: Emerging Materials and Refractory Metals
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee, TMS: Refractory Metals Committee
Program Organizers: Akane Suzuki, GE Global Research; Martin Heilmaier, Karlsruhe Institute of Technology (KIT); Pierre Sallot, Safran Tech; Stephen Coryell, Special Metals Corporation; Joseph Licavoli, NETL - Department of Energy; Govindarajan Muralidharan, Oak Ridge National Laboratory

Tuesday 8:30 AM
February 28, 2017
Room: Pacific 16
Location: Marriott Marquis Hotel

Session Chair: Pierre Sallot, Safran; Don Lipkin, GE Global Research

8:30 AM  Keynote
Advanced Aerospace Engine Requirements and Materials Development: Francis Preli1; 1Pratt & Whitney
    Next generation engine design, such as advanced versions of the Pratt & Whitney PurePower™ PW1000G engine with Geared Turbofan™ technology and the F135 engine for the F-35 Joint Strike Fighter must balance product requirements of higher performance, reduced weight and lower cost. The desire to reduce the environmental footprint and the cost of aircraft engine operation increases the need to reduce fuel burn. More efficient engines generally tax the temperature capability of materials systems and put pressure on the designers to reduce weight. In addition, these materials must be durable enough to perform over ever-increasing service intervals. The current state of the art turbine engine materials will be reviewed as well as options to meet future requirements.

9:00 AM  Invited
Ceramic Matrix Composites for Jet Engine Applications: Damage Mechanisms and Design: Gregory Morscher1; 1University of Akron
    Ceramic matrix composites are now being inserted into commercial jet engines. They possess superior high temperature strength, lower density and greater temperature capability compared to superalloys. Being a fiber-reinforced composite structure they do possess some toughness. However, ceramic matrix composites are considerably more brittle than superalloys and the nature of damage accumulation is quite different compared to superalloys. In this presentation, an overview of ceramic matrix composite damage mechanisms as they relate to stressed-oxidative life properties will be presented as well as some design considerations. In addition, some of the approaches to mitigate these issues will be discussed.

9:30 AM  Invited
Creep and Oxidation Resistance of Select MAX Phases: A Critical Review: Michel Barsoum1; Sankalp Kota1; 1Drexel University
    Before the MAX phases can be used as high temperature structural materials their resistance to creep and oxidation need to be well understood. Of all the MAX phases, the most resistant to oxidation are Ti2AlC, Ti3AlC2 and Cr2AlC. A literature review shows that some claim that the oxidation kinetics to be parabolic, others cubic. At this time, there is little doubt that the oxidation kinetics are cubic. The tensile and compressive creep results of Ti3SiC2 and Ti2AlC, with varying grain sizes in the 1000–1200 C temperature range, suggest that ripplocations and grain boundary sliding are the dominant creep mechanisms. A comparison of the creep properties of Ti3SiC2 with other high temperature materials suggests that it can be used at higher temperatures but only if the applied stresses are low.

10:00 AM Break

10:20 AM  Invited
Oxidation of Alumina-forming MAX Phases in Turbine Environments: James Smialek1; Anita Garg1; Bryan Harder1; James Nesbitt1; Timothy Gabb1; 1NASA Glenn Research Center
    High temperature turbine components require oxidation resistance or coatings. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that approaches Al2O3 and YSZ. Their Al2O3 scales grow according to cubic kinetics, with initial heating dominated by fast TiO2 growth. MAXthal 211 'Ti2AlC' survived high pressure burner tests up to 1300C, with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on Ti2AlC exhibit remarkable durability up to 1300C in furnace tests, with at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy. Accordingly, sputtered Cr2AlC coatings helped prevent hot corrosion detriments in LCF of a disk alloy. Breakaway oxidation, scale spallation, interdiffusion, and coating processing still present challenges. However the properties of MAX phases provide some unusual opportunities in turbines.

10:50 AM  Invited
Toughness and High Temperature Strength of Nb-Si and MoSiBTiC Alloys: Nobuaki Sekido1; Junya Nakamura1; Kyosuke Yoshimi1; 1Tohoku University
    Alloys based on refractory metal silicides have been considered as potential candidate materials that can be equipped with a temperature capability superior to Ni based superalloys. While alloys based on the Nb-Si and Mo-Si-B systems, as well as TiC doped Mo-Si-B alloys (referred as MoSiBTiC alloys) have been shown to exhibit some attractive material performance in terms of room temperature toughness, high temperature strength, and oxidation resistance, there are still some challenges that have to be overcome to satisfy these conflicting property requirements. In this talk, our recent development on the Nb-Si alloys and MoSiBTiC alloys will be reviewed. We will also discuss the room temperature deformation capability of the monolithic silicides, which is examined by nano-mechanical testing.

11:20 AM  
Scalable Processing, Microstructure, and Mechanical Properties in Mo-matrix Mo-Si-B: Peter Marshall1; Oliver Strbik2; 1Imaging Systems Technology; 2Deep Springs Technology
    The design and development of Molybdenum matrix, Mo-Si-B materials for high temperature and oxidizing structural applications has shown promise for increasing operating temperatures, with the particular advantage of a tough, metallic matrix. The refractory three phase microstructure of a Mo matrix containing Mo3Si (A15) and Mo5SiB2 (T2) grains results in high hot strength and creep resistance up to 1300C. Further, at high temperatures a borosilicate surface scale can form from the intermetallic phases providing oxidation resistance. The refectory nature of molybdenum and its mechanical sensitivity to impurities are challenges for scalable and cost effective processing. Powder techniques can produce molybdenum matrix material however the sintering temperature, material purity, and silicon supersaturation must be balanced. The impact of these factors upon the ductile to brittle transition temperature, high temperature strength, and creep resistance have been investigated and the results used to inform further development and scale-up.