This paper contains a description of some recent progress on impression creep testing and its applications. Several fundamental aspects, involving the conversion relationships, typical test types, and validity of the test technique, are briefly described. Applications of the test data to assist with the life assessment of components, particularly those with service-exposed materials, using data obtained from scoop samples, are outlined. Correlations of impression data with the corresponding uniaxial data, where available, and with corresponding hardness results, are presented. These results indicate that the impression creep test method is a potential, simple, and economic life assessment technique for power plant life assessment applications. Proposals for future exploitation and for improvement of the technique are addressed.

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A mode of cracking termed Type IIIa has been found to occur in the welds of ½CrMoV pipework systems in the UK. This cracking mechanism is not as well documented as the more familiar Type IV cracking, which occurs on these and other ferritic steel systems, but is likely to increase in importance as plant ages. This paper summarises the available information on the initiation and development of Type IIIa cracks and brings up to date recent work on carbon diffusion local to welds, which is believed to play a role in the susceptibility to this form of cracking.STWJ/387

When dissimilar welds are heat treated or exposed to in service conditions, long range diffusion of rapidly diffusing elements can be induced by strong gradients in chemical potential across the fusion zone. This diffusion is usually accompanied by precipitation or dissolution of carbides and nitrides. In the present work, six 2·25Cr/9Cr and 2Cr/0·5CrMoV welds in different heat treatment conditions have been characterised by means of optical and electron microscopy. Carbon profiles have been obtained with wavelength dispersive X-ray analysis. A general thermokinetic model for simultaneous precipitation and diffusion, which is implemented in the software MatCalc, has been used to predict the time dependent phase distributions and the carbon profiles based on multicomponent thermodynamic and kinetic data. The calculations and the experimental data show good agreement.

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