Conventional and tomographic atom probe investigations of secondary‐hardening carbides

Abstract

AbstractSecondary‐hardening carbides in high‐speed steels are very important microstructural constituents responsible for the excellent properties of these steels in cutting applications, therefore detailed knowledge about their precipitation reactions and coarsening behaviour is of great interest.The investigations were carried out on steel grades HS2‐10‐1‐8 and HS6‐5‐2 with nominal chemical compositions (in wt.%) of 1.1C–3.9Cr–1.4W–9.2Mo–1.2V–8Co (HS2‐10‐1‐8) and 0.9C–4.1Cr–6.4W–5Mo–1.8V (HS6‐5‐2). The austenitizing temperatures for HS2‐10‐1‐8 and HS6‐5‐2 were 1190°C and 1210°C, respectively. After quenching, the samples were heated non‐isothermally from room temperature to different final temperatures at 15 K min−1. The resulting precipitates were analysed to determine composition, size and morphology using both a conventional one‐dimensional atom probe and a three‐dimensional tomographic atom probe. The results obtained by both techniques from samples at different heat treatment conditions are compared. Owing to the different evaporation field of the precipitates, an overlap of the ion trajectories from matrix and precipitates can be observed. Methods to correct the analytical results are discussed. Copyright © 2004 John Wiley & Sons, Ltd.