Metallic replica technique for residual life assessment for components serviced in creep regime

Abstract

Summary For 9–12% Cr creep-resistant steels, a new kind of replica, contemporaneously morphological and extractive, is nowadays in use. This method is non-destructive and ‘in situ’ applicable via a customised portable equipment and allows the study of the steel microstructure evolution during in-service inspections. The technique produces a neat imprint of the steel microstructure, like a morphological replica, but contemporaneously extracts particles down to 15–20 nm diameters. The use of a good electrical conductor extraneous to the steel composition as a replication basis allows the investigation of the martensitic (sub-) microstructure together with the particle distribution, nanometric dimensional and chemical analyses using a tungsten electrode scanning electron microscope at magnifications up to 500000×. For component residual life assessment, besides a measuring technique and a damage witnessing criterion, a reference is needed against which spent lifetime through which or actual damage can be estimated. .