The mechanisms involved in the breakdown of the protective ccides formed on Fe-9%Cr l%Mo have been investigated in both air and high pressure CO 2' The initial research programme was to investigate the microstructural changes which occurred with breakaway oxidation, a new EELS detector being cxi missioned to detenni. ne oxygen and raXbon levels. Oxidation in air was performed at temperatures between 500 and 1000'C. SEM and sane TEN cross sectional work was performed to determine the role of oxygen ingression, but prcblems in sample preparation made examination difficult. With cDcidation in high pressure OD2 the change from protective growth to breakaway is accanpanied by massive oxide growths usually at specimen corners. Microstructural changes also occur, with massive carbide growth acccrnpanying the changes in oxide structure. During oxidation, chemical exchanges between the oxidising gas, the metal and the inner oxide all contribute to the deposition of carbon at the metal/ oxide interface. This process generates internal stresses in the oxide, allowing microcracks to develop this enhancing the inward movement of the 002 and causing more, oxidation and carbon deposition. TEM cross sections were prepared to determine the mode of oxidation and the process by which carbon reaches the interface. In theory, EELS analysis allows identification of light elements Mi and above) but in practice the system proved very sample dependent, working well on thin films but very poorly on thick specimens (carbides). Evidence of the range of EELS mapping facilities are presented together with work on a new particle extraction system
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:234829 |
| Date | January 1987 |
| Creators | Baxter, A. G. |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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