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Title: Microstructure and mechanical properties of NiCoCrAlYTa alloy processed by press and sintering route

Nickel-based superalloys such as NiCoCrAlY are widely used in high-temperature applications, such as gas turbine components in the energy and aerospace industries, due to their strength, high elastic modulus, and high-temperature oxidation resistance. However, the processing of these alloys is complex and costly, and the alloys are currently used as a bond coat in thermal barrier coatings. In this work, the effect of cold press and sintering processing parameters on the microstructure and mechanical properties of NiCoCrAlY alloy were studied using the powder metallurgy route as a new way to obtain NiCoCrAlYTa samples from a gas atomized prealloyed powder feedstock. High mechanical strength and adequate densification up to 98% were achieved. The most suitable compaction pressure and sintering temperature were determined for NiCoCrAlYTa alloy through microstructure characterization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy microanalysis (EDS) were performed to confirm the expected γ-Ni matrix and β-NiAl phase distribution. Additionally, the results demonstrated the unexpected presence of carbides and Ni–Y-rich zones in the microstructure due to the powder metallurgy processing parameters used. Thus, microhardness, nanoindentation and uniaxial compression tests were conducted to correlate the microstructure of the alloy samples with their mechanical propertiesmore » under the different studied conditions. The results show that the compaction pressure did not significantly affect the mechanical properties of the alloy samples. In this work, the compaction pressures of 400, 700 and 1000 MPa were used. The sintering temperature of 1200 °C for NiCoCrAlYTa alloy was preferred; above this temperature, the improvement in mechanical properties is not significant due to grain coarsening, whereas a lower temperature produces a decrease in mechanical properties due to high porosity and poor solid-state diffusion. - Graphical abstract: Display Omitted - Highlights: • We made NiCoCrAlYTa alloy by a conventional powder metallurgy route. • High densification and adequate strength were observed. • The presence of unexpected carbides found along γ/γ and γ/β grain boundaries was detected. • The effect of cold press and sintering processing parameters on the microstructure and mechanical properties were studied.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [1]
  1. Instituto de Tecnología de Materiales, Universidad Politécnica de Valencia, Camino de vera s/n, Valencia, España (Spain)
  2. (Venezuela, Bolivarian Republic of)
  3. Centro de Investigaciones en Mecánica, Facultad de Ingeniería, Universidad de Carabobo (Venezuela, Bolivarian Republic of)
  4. Departamento de Engenharia de Materiais, Universidade Federal de São Carlos (UFSCar), São Carlos, SP (Brazil)
Publication Date:
OSTI Identifier:
22476061
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 101; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AEROSPACE INDUSTRY; ALLOY SYSTEMS; ALUMINIUM COMPOUNDS; COBALT COMPOUNDS; DIFFUSION; GRAIN BOUNDARIES; HEAT RESISTING ALLOYS; MICROANALYSIS; MICROHARDNESS; NICKEL COMPOUNDS; POROSITY; POWDER METALLURGY; PRESSURE RANGE MEGA PA; SCANNING ELECTRON MICROSCOPY; TANTALUM COMPOUNDS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; YTTRIUM COMPOUNDS