Study of the structure and mechanical properties of engineering products made of austenitic-martensitic steel, using the metal magnetic memory technique

Abstract

Spontaneous phase transformation in local areas of the austenitic microstructure to martensite with the release of carbides may appear during the manufacturing or operation of engineering products made of two-phase austenitic-martensitic steel grades. When inspecting the quality of products made of these steels, the problem of detecting the local zones of the martensitic phase and carbide precipitation in the product metal arises. The article presents the results of an inspection by means of the metal magnetic memory (MMM) technique of centrifugal compressor impellers made of austenitic-martensitic steel 07Cr16Ni6. It was demonstrated that in the areas of stray field indications detected by means of the MMM technique, strength properties deteriorate, the metal structure degrades with abrupt changing of the metal phase composition and a carbide network formation, unacceptable δ-ferrite, was detected in the structure, and micro- and macro-cracks were found.