Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1635473 | Rare Metals | 2006 | 11 Pages |
Abstract
When a moderately stable phase is precipitated out during an internal reaction, the behaviour of the penetrating atoms within the diffusion zone can be interpreted based on thermodynamic considerations. Evidence for “up-hill” diffusion of the penetrating species through the matrix towards the precipitation front during the internal nitridation of Ni-Cr alloys at 1125°C and 6000 bar of N2-pressure was predicted. Such behaviour of nitrogen is opposite to the boundary conditions in Wagner's description of internal reactions. A volume change associated with the precipitation reaction resulted in a stress gradient between the alloys surface and the internal nitridation front. Stress relief occurred mainly by transport of nickel to the gas/metal interface. Pipe diffusion-controlled creep is the dominant stress accommodation mechanism during nitriding of dilute Ni-Cr alloys at 700°C under a flowing NH3 + H2 gas mixture.
Related Topics
Physical Sciences and Engineering
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Authors
Alexander A. Kodentsov, Jorma K. Kivilahti, Frans J.J. van Loo,