Dissertation > Excellent graduate degree dissertation topics show

Isothermal Oxidation Behavior of DZ792Superalloy

Author: ZhaoZhuo
Tutor: WangLei
School: Northeastern University
Course: Materials Science
Keywords: DZ792alloy high temperature oxidation oxidation dynamics oxidation scales oxidation mechanism
CLC: TG132.32
Type: Master's thesis
Year: 2009
Downloads: 37
Quote: 0
Read: Download Dissertation

Abstract


DZ792alloy is a directionally solidified Ni-base superalloy by directional solidification technology, which is based on IN792alloy after the little changing of the alloy elements. DZ792alloy is mainly applied to the gas turbine blades. Comparing with the servicing condition of aeroengine, the gas turbine for the heavy industry is undergoing more severely condition and longer time. At the same time, since it usually used without any coating, the oxidation resistance will be more and more important. So, not only the mechanics performance but also both the excellent oxidation and corrosion resistance at high temperatures are asked. Therefore, it is very important for safety servicing to accurately evaluate the oxidation resistance of an alloy, and it is also useful for the developing new alloy and improving the same kind of alloys.In the present study, the oxidation characteristics of DZ792alloy were system estimated under static atmosphere at750～950℃up to500h, according to the commen working condition of the alloy. The microstructure, morphologies and components of the oxidized scales were synthetically examined by an optics microscope (OM), an X-ray diffraction (XRD) and a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (SEM/EDX). The oxidation rules of DZ792and the main effect factors of the oxidation characteristics were summarized, and the oxidation mechanism was also discussed.It has been found that the oxidation kinetics curves of DZ792follows parabolic law in a temperature range of750～950℃during isothermal oxidation under static atmosphere. The diffusion activation energy O is to be about244.86kJ·mol-1fitted from the kinetics curve, so it can be considered that the oxidation within this temperature ranger is mainly controlled by Cr3+diffusion among Cr2O3oxidation scale. Based on the calculation results of oxidation velocity constant K, it can be estimated that the oxidation resistance grade of DZ792alloy is complete anti-oxidation within750～850℃, and anti-oxidation within900～950℃. Considering of the integrative performance of the alloy, it is suggested that the optimal servicing temperature is in the range of750～850℃. The oxidation products are mainly consist of Cr2O3, TiO2, TiTaO4and NiCr2O4as well as the Al2O3and TiN which is the inside oxidation products. The oxidation scale can be divided into several zones in the order of TiO2, CrO3+TiTaO4+NiCr2O4, Al2O3and TiN, from the surface to inside. During the oxidation, the surface, the carbides, grain boundaries and eutectic of the hypo-surface can be easily oxidized, whose priority oxidation accelerated the oxidation behavior of the alloy. The oxidation of Ti element and the depletion of Cr element led to the inside oxidation of Al element, which will influence the steady growth of the oxidation scales, so that the oxidation resistance decrease.

Related Dissertations

  1. Research on Microstructures and Properties of FeMnCrNiAlBSi/Cr3C2 Coatings,TG174.44
  2. Studies of Plasma Spray Metal-Ceramic Compounds Coatings on Q245r Steels,TG174.44
  3. Microstructure and Properties of 9Cr-ODS RAFM Prepared by PM,TG142.1
  4. Study on the Preparation and Thermostability for Mechanical Properties Microstructure of Low Density MA/ ODS Nickel-Based Superalloy,TG132.32
  5. Effect of Pre-Oxidation Treatment on the Service Life of Thermal Barrier Coating,TG174.4
  6. Research on Microstructure and Properties of Ti(C, N)-based Cermets Coated by Multivariant Nitrides,TG174.4
  7. Preparation of Al2O3 Coating on Steel Substrate,TG174.4
  8. Pulse Nanocomposite Coatings Preparation and Properties,TQ153
  9. Titanium sponge reactor temperature oxidation resistant coating Preparation and Mechanism,TG174.442
  10. Prepared by reaction infiltration C_f / (HfC MC) Mechanism and Properties of Composite Materials,TB332
  11. Nano zirconia thermal barrier coatings prepared by plasma spraying and Properties,TG174.442
  12. Research on High-temperature Oxidation Property of Calorized Coatings on GH907 Superalloys,TG174.44
  13. Preparation and Properties of Functional Composite Coatings Embedded ZrO2 Ceramic Particles,TG174.4
  14. Study on High Silicon Coating by Dc-Plasma Jet Surface Metallurgy,TG174.4
  15. Research on High-temperature Oxidation Resistance and Corrosion Resistant of Several Ni-Based Metals,TG132.32
  16. The Preparation and Properties of Ternary Boride Mo2 FeB2 Based Cermets,TG148
  17. Preparation of Gold-Maghemite Nanocomposites,TB383.1
  18. TiAl Alloys SPS sintering of Microstructure and High Temperature Oxidation,TF124.5
  19. Laser Direct Metal Deposition (DMD) of Ni-Base Superalloy and Its High Temperature Oxidation Resistance,TF124.39
  20. Corrosion Behavior of Bulk Nanocrystalline 304 Stainless Steel,TG172
  21. Research on High Temperature Performance of Mould Materials with High Current Pulsed Electron Beam Alloying,TG174.4

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Special physical properties of alloys > Special thermal properties of alloys > Melting point alloys , refractory alloy , high temperature alloys
© 2012 www.DissertationTopic.Net  Mobile