Energy Materials 2017: Materials for Coal-Based Power: Poster Session
Sponsored by: Chinese Society for Metals
Program Organizers: Jeffrey Hawk, U.S. Department of Energy, National Energy Technology Laboratory; Zhengdong Liu, China Iron & Steel Research Institute Group; Sebastien Dryepondt, Oak Ridge National Laboratory
Monday 6:00 PM
February 27, 2017
Room: Hall B1
Location: San Diego Convention Ctr
C-3: Atomic-scale Modeling of Point Defects, Phase Stability, and the Formation Mechanism of Z Phases CrMN (M=V, Nb, Ta): Daniel Urban1; Christian Elsaesser1; 1Fraunhofer IWM Freiburg
The challenge of raising the steam inlet temperature of fossil-fired power plants calls for creep-resistant steels with a Cr content higher than 9% to achieve sufficient corrosion and oxidation resistance. However, it has been observed that in 11-12% Cr steels strengthened by fine (V,Nb)N particles, precipitation of coarse Z-phase particles, CrMN (M=V,Nb,Ta), in long-term service is unavoidable and detrimental. Hence the task is to control the precipitation of the Z-phase such that fine and long-term stable particles are formed. We present atomistic simulations, using density functional theory, which reveal the mechanisms underlying the formation of Z-phases. The scenario consists of the diffusion of Cr atoms into MN particles and their subsequent clustering in a layered arrangement which finally yields the transformation of (V,Nb)N to Z-phase particles. We study the thermodynamic stability of the Z phase, related structures and predecessors as well as basic phase-formation mechanisms.
C-5: Fireside Corrosion Behaviors of Inconel 740 H Superalloy in Various SO2 Contents: Jintao Lu1; 1Xi′ an Thermal Power Research Institute Co., Ltd.
Fireside corrosion behavior of Inconel 740H superalloy was studied at 750℃ in simulated coal ash/flue gas environments by means of XRD, SEM and EDS. The results indicated that the corrosion behavior was strongly related to the SO2 levels and was significan tly affected by NaCl additions. In presence of the atmospheres with 0.1% SO2, the alloy exhibited the highest corrosion resistance due to formation of a stable and dense Cr2O3 film. In present of the atmosphere with 1.5% SO2, however, a non-coherent and porous Cr2O3 film was formed. The thickness of film and internal sulfides were substantially increased. The mechanism of ash corrosion formation was also discussed.
C-6: High Cycle Fatigue Behavior of HAYNES282 Superalloy: Ming Yang1; 1Dongfang Electric Corporation. Don gfang Turbine Co.LTD
This paper has carried out high cycle fatigue performance test for Haynes282 nickel-based alloy at room temperature, 700 ℃and 760 ℃. The optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the change features of microstructure and fracture. The results showed that the precipitation of γ′ phase which makes alloy has excellent high cycle fatigue performance is a guarantee of high strength of this alloy, and fatigue strength reduced slowly with the temperature increasing. The fracturing pattern was in monophyletic fatigue source, and extended in the form of cleavage and quasi cleavage and had obvious river pattern characteristics. At the same time, the fatigue crack propagation in the form of dislocation slip extension, and the coarsening of γ′ hinder the dislocation sliding and climbing as the temperature rise, which made for improving the fatigue strength of alloy.
C-7: Recent Development in the Characteristics of Alloy 625 for A-USC Steam Turbine Castings: Wenlong Yu1; Songfeng Liu1; Yu Wang1; Lingen Sun1; 1Shanghai Turbine Company, Ltd.
Raising the operating temperature and pressure of the steam turbine can improve the thermal efficiency in order to reduce the fossil fuel consuming and CO2 emissions. Alloy 625 is a solution strengthened Ni-base superalloy and has been considered as one possible candidate for A-USC steam turbine castings. In this research, we investigate the microstructure, tensile and creep behavior, low cycle fatigue property and long-term thermal stability of Alloy 625, which was produced by sand casting. The alloy exhibits excellent creep properties and thermal stability. Nb segregation has been found in the thick section and cannot be eliminated by heat treatment. The segregation can influence the mechanical properties and cause defects in large casings and valves. Alloy 625 can meet the design requirements of A-USC steam turbine, but also need further research on production process.
C-8: The Effect of W and Mo Addition on the Microstructure and Mechanical Properties of GY200 Ni-based Alloy: Zhihua Gong1; Gang Yang2; 1Inner Mongolia University of Science & Technology; 2Central Iron and Steel Research Institute
In this investigation, six GY200 alloys with different tungsten and molybdenum contents were designed through composition optimization. SEM, TEM and chemical analysis method were carried out to illustrate the effect of W and Mo addition on the microstructure and mechanical properties of GY200 alloy. The results show that optimized W and Mo addition in GY200 alloy would lead to higher strength and a slight decrease of ductility. For alloys separately added W (Mo free), higher W content results in higher contents of MC and γ’ precipitates, while the peak value of M23C6 content were found in alloy containing 4% W. Moreover, the addition of 2% Mo in GY200 alloys exerts favorable influence on to the precipitation behavior of MC and γ’. However, increased W addition from 2~4% brought about a sharp decrease of M23C6 content, while the content raised again for alloy containing 8% W.