Optical metallography of some maraging steels

Abstract

The structural features of maraging steels including those that impose limitations on strength and toughness are briefly reviewed. Phase relationships in the iron-nickel matrix system are introduced which in conjunction with alloy composition and heat treatment allow the interpretation of microstructure. Details are presented of methods for revealing the microstructure of maraging steels; the prior austenite grain size following a variety of heat treatments is of special interest since excessive grain size can lead to poor ductility. These methods are illustrated with micrographs of the microstructures of MAR 350 and MAR 400 steels in the cast solution-treated aged and cold-worked states.