Author: Skelton, R.P.

Source: Materials at High Temperatures, Volume 23, Number 1, February 2006 , pp. 39-54(16)

Publisher: Science Reviews 2000 Ltd

Abstract:

'Down' and 'up' thermal shock experiments on cast and forged forms of 9/12Cr steels and their weldments at a maximum temperature of 565°C have demonstrated a marked reluctance to form traditional craze cracking and propagation into the body. However, in specimens of ex-service cast 1CrMoV material tested to the same number of cycles (1000), initiation and growth of (intergranular) cracks is much more likely in layers near the inner surface of the component than in layers deep within the section. This is due to the effect of prior thermal cycling of the inner material during start up and shut down events.

Thermal shock and isothermal tests at a maximum temperature of 550°C on ½CrMoV/2¼Cr1Mo weld features have indicated that crack propagation is generally along the fusion boundary (though for some cases, in the weld metal itself) and that cyclic growth rates lie close to an upper bound law valid for ferritic steels. The results from laboratory tests are compared with service experience as regards stresses generated, likely crack path and possibility of arrest.

Keywords: downshock; upshock; cylindrical shell; residual stress; temperature/stress gradient; fusion boundary cracking; stress intensity factor; transgranular/intergranular cracking

Document Type: Research article

DOI: http://dx.doi.org/10.3184/096034006782739420

Affiliations: 1: Consultant, c/o Science Reviews, PO Box 314, St Albans, Herts AL1 4ZG, UK., Email: pskelton@scilet.com

Publication date: 2006-02-15

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• Materials at High Temperatures serves the needs of those who develop and use materials for high temperature applications. It publishes peer reviewed contributions relating to high temperature applications in the power, chemical, engine, processing and furnace industries.

  The effects of high temperatures on corrosion, fatigue, creep, strength and wear in alloys, intermetallics, ceramics, refractories and composites are covered. Papers dealing with aspects of materials usage including modelling of behaviour and life prediction will be particularly welcome. The journal has a policy of emphasizing practical aspects and authors presenting results from research programmes are encouraged to relate these, if possible, to actual or potential applications.

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