Abstract
In service components such as steam pipes, pipe branches, gas and steam turbine blades, etc. which operate in engineering applications such as power plant, aero-engines, chemical plant etc., can operate at temperatures which are high enough for creep to occur. Often, only nominal operating conditions (i.e. pressure, temperatures, system load, etc.) are known and hence precise life predictions for these components, which may be complex in terms of geometry or weld characteristics, are not possible. Within complex components it can also be the case that the proportion of the material creep life consumed may vary from position to position within the component. It is therefore important that non-destructive techniques are available for assisting in the making of decisions on whether to repair, continue operating or replace certain components. Small specimen creep testing is a technique which can allow such analyses to be performed. Small samples of material are removed from the component to make small creep test specimens. These specimens can then be tested to give information on the remaining creep life of the component. This paper presents the results of small ring specimens tested under creep conditions and shows the comparison to standard (full size) creep testing for materials used under high temperature in industry.
Highlights
In many cases it is desirable to achieve standard creep data from of pieces of material which are too small to manufacture conventional uniaxial specimens
These advantages include the fact that any material, including highly creep resistant materials such as nickel-based superalloys, can be tested, as is the main topic of this paper
The current work, which shows the method applied to the root of an ex-service blade made of Inconel 738 material, is extremely encouraging when compared with conventional uniaxial data
Summary
In many cases it is desirable to achieve standard creep data (see Figure 1) from of pieces of material which are too small to manufacture conventional uniaxial specimens (see Figure 2). A few different small specimen creep test types have been developed over recent years Such small specimen types are required for applications such as operating power-plant steam pipes, from which a small amount of material can be removed from the in-service component. This paper shows the results SR testing of a Nickel-based superalloy (which is not possible with other small specimen types, as discussed in section 2.2) and gives a description of the major advantages of this specimen type
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