High temp. multilayer wall structure - with iron or nickel alloy core contg. carbide formers

摘要

A multilayer wall structure for high temp. use, has a Fe and/or Ni alloy core layer with a corrosion resistant thin surface layer of dense oxide film-forming material on one or both sides, the novelty being that the core layer has a content of stable carbide-formers such that the carbon activity of the core layer at the prodn. and operating temp. is not greater than that of the surface layer. The carbide-former is pref. selected from e.g. V, Nb, Ta, Hf, Zr and Ti present in stoichiometric amount for carbide formation w.r.t. the carbon content of the core layer. The core layer pref. consists of a Fe or Ni alloy contg. 2-5% Nb, opt. (partially) replaceable by Ti, Zr, Ta, Hf and/or V, and has a Cr-contg. surface layer.