High Temperature Oxidation Behavior of the Niobium-tungsten-chromium System and Response of Boron Additions

High Temperature Oxidation Behavior of the Niobium-tungsten-chromium System and Response of Boron Additions

4.11 - 1251 ratings - Source



Niobium based super alloys are necessary to fill the rising need in the aerospace industry for materials that can perform for extended times extreme environments at elevated temperatures near the melting point of nickel. Unfortunately niobium has very low oxidation resistance at elevated temperatures based on several studies that have been undertaken to remedy this problem resulting in several complex alloys that have yet to offer performance near that of nickel super alloys. In this study the oxidation behavior of several compositions including a single phase and a two phase alloy containing the NbCr laves phase of the Nb-Cr-W system will be evaluated as well as the system's response to boron additions. Oxidation samples were subjected to a short term oxidation (STO) treatment of 24hrs at temperatures ranging from 700 to 1400AdC. A long term cyclic oxidation (LTO) study was also carried out to 168hrs (one week) in 24hr intervals at temperatures ranging from 1200 to 1400AdC. Another set of samples were subjected to a heat treatment in an argon inert atmosphere for 24hrs at 1400AdC. Oxidation products were characterized using scanning electron microscope (SEM), back scatter electron imaging (BSE), x-ray diffraction (XRD), and x-ray photo spectroscopy (XPS) analyses techniques. SEM and BSE imaging techniques revealed the presence of chromium rich and tungsten depleted particles dispersed in the bulky solid oxidation products. XPS and XRD techniques revealed four oxides present in all oxidation products: Nb2O 5, Cr2O3, WO3, and in most cases NbCrO 4. Long term oxidation data was found to indicate that the addition of boron was detrimental to the oxidation resistance of the alloys over long periods of time. The single phase alloys with a boron addition were found to have undergone chromium segregation in response to the 0.1wt% boron addition after the argon inert atmosphere heat treatment. This study reports the oxidation behavior of various alloys from the Nb-Cr-W alloy system and confirms the chromium segregation in the single phase alloys in response to boron additions.3.5.2 Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) Elemental analysis was carried out on the surfaces of the oxide ... The SEM used was a Hitachi FESEM 8700 and a Philips Electroscan ESEM 2020 with 11.


Title:High Temperature Oxidation Behavior of the Niobium-tungsten-chromium System and Response of Boron Additions
Author:
Publisher:ProQuest - 2008
ISBN-13:

You must register with us as either a Registered User before you can Download this Book. You'll be greeted by a simple sign-up page.

Once you have finished the sign-up process, you will be redirected to your download Book page.

How it works:
  • 1. Register a free 1 month Trial Account.
  • 2. Download as many books as you like (Personal use)
  • 3. Cancel the membership at any time if not satisfied.


Click button below to register and download Ebook
Privacy Policy | Contact | DMCA