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A study has been made of the initial stages of oxidation of yttrium ion implanted Ni-20Cr in an attempt to shed some light on the reactive element effect observed in chromia forming alloys. ReflEXAFS was used in order to observe the initial local atomic structural changes around the implanted ions, while glancing angle X-ray diffraction was used to monitor the longer range structural transformations taking place near the surface. The results indicated that the implantation amorphised the alloy surface. Following a short oxidation at 700 C Y(2)O(3) nanocrystals formed throughout the implanted region. Simultaneously a highly oriented Cr(2)O(3) layer formed on the sample surface. Preliminary measurements reported here on the thermal expansion of hexagonal chromium oxide indicate a pronounced anisotropy with respect to the crystallographic direction, which could explain the superior adhesion to the substrate alloy of oriented scales under conditions of thermal cycling.

Additional information

Authors: GIBSON P N, JRC Ispra (IT);CRABB T A, University of Strathclyde, Department of Pure and Applied Chemistry, Glasgow (GB)
Bibliographic Reference: Paper presented: Synchrotron Radiation Material Science, Chester (GB), July 3-8, 1994
Availability: Available from (1) as Paper EN 38401 ORA
Record Number: 199511256 / Last updated on: 1995-10-13
Original language: en
Available languages: en
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