Improving resistance to dynamic embrittlement and intergranular oxidation of nickel based superalloys by grain boundary engineering type processing
| Autor: | Ulrich Krupp, W. M. Kane, C.J. McMahon, P. E.-G. Wagenhuber |
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| Rok vydání: | 2005 |
| Předmět: | |
| Zdroj: | Materials Science and Technology. 21:1247-1254 |
| ISSN: | 1743-2847 0267-0836 |
| DOI: | 10.1179/174328405x63935 |
| Popis: | Polycrystalline nickel based superalloys are prone to grain boundary attack by atmospheric oxygen either in the form of time dependent intergranular cracking during dwell time within a low cycle fatigue loading spectrum, known as hold time cracking, or in the form of intercrystalline oxidation at higher temperatures. In the case of hold time cracking of IN718 it has been shown that the crack propagation velocity is determined by local microstructure and environmental conditions, reaching values up to 10 μm s−1 under four-point bending conditions at 650°C in air. The governing mechanism for this kind of time dependent quasi-brittle intergranular failure has been recognised to be 'dynamic embrittlement', i.e. diffusion of the embrittling element into the elastic stress field ahead of the crack tip, followed by stepwise decohesion. In a very similar way to intercrystalline oxidation, this damage mechanism seems to depend on the local microstructure. Assuming that oxygen grain boundary diffusivity is ... |
| Databáze: | OpenAIRE |
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