Electromagnetic evaluation of the microstructure of Grade 91 tubes/pipes

Research output: Contribution to journalArticlepeer-review


  • John Wilson
  • Anthony Peyton
  • Jonathan Parker

Colleges, School and Institutes

External organisations

  • University of Manchester
  • Electrical Power Research Institute, 1300 West W.T. Harris Boulevard, Charlotte NC 28262, USA


This 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/mis-manufactured Grade 91 steel tubes/pipes from the correctly heat treated service-entry ones.


Original languageEnglish
Pages (from-to)65-71
Number of pages7
JournalInternational Journal of Pressure Vessels and Piping
Early online date3 Jun 2015
Publication statusPublished - 1 Aug 2015


  • Grade 91 steel, EM sensor, Relative permeability, BH loop, Tube