Electromagnetic evaluation of the microstructure of Grade 91 tubes/pipes

Abstract

a b s t r a c tThis paper assesses the feasibility of transferring a laboratory-based electromagnetic (EM) sensor technique, which has already proved sensitive to significant (e.g. phase balance) or subtle (e.g. number density of fine precipitates) microstructural changes in steel, to non-destructive evaluation of the microstructure of power generation components such as tubes/pipes. It has been found that Grade 91 steels, in different conditions representative of service entry, thermally aged or ex-service, can be distinguished using laboratory-based measurement systems on small machined cylindrical samples as well as by an industry deployment EM sensor system on full-diameter tube samples. The measurements for the tube samples follow the same trend as the machined cylindrical samples. The results indicate an industrial deployable sensor system can be used for sorting service-exposed or mis-heat-treated/mismanufactured Grade 91 steel tubes/pipes from the correctly heat treated service-entry ones.

Destructive and non-destructive testing methods for characterization and detection of machining-induced white layer: A review paper

“…In this grind-hardening study, it was found that the RMS of the BN signal decreased with increasing hardening depth, as would be expected due to the larger percentage of magnetically hard material in the inspection volume. Similarly, Liu et al (2015) and Wilson et al (2014) were able to successfully distinguish between different heat treatments in grade 91 steel tubes and pipes using BN and coercivity measurements. In this case, the microstructure of the steel, both in terms of the phases present and the precipitate density, influenced the NDT measurement.…”

Magnetic Stress Monitoring Using a Directional Potential Drop Technique

“…Such changes are likely to be long-term, monotonic, and approximately isotropic and may therefore be separable from the influence of at least dynamic loading. It has been suggested in previous literature that it may be possible to use magnetic properties to monitor the microstructural state of engineering components [ 18 – 20 ]. This study has shown that various parameters including stress state, temperature and magnetisation cause significant changes in magnetic permeability and are likely to dominate the subtle influence of microstructural evolution.…”

Passive thermoelectric power monitoring for material characterisation

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“…In particular, electromagnetic properties have been seen as particularly promising due to the high sensitivity to numerous microstructural features and the possibility of simple and robust measurement hardware. 2,3 Studies into electrical [4][5][6] as well as a range of magnetic and micromagnetic properties [7][8][9][10] have been conducted. This article will focus on Seebeck coefficient, or 'thermoelectric power' (TEP), as an example, but many of the issues investigated will be common to a range of other properties.…”