Senior consultant, E. I. du Pont de Nemours and Co., Inc., Wilmington, Del.
Pages: 65 Published: Jan 1977
High chromium-ferritic stainless steels have good general corrosion and pitting resistance and are resistant to stress-corrosion cracking. Despite these desirable properties, the alloys have found little use as materials of construction. This lack of use is a result of significant losses in ductility, toughness, and corrosion resistance when these alloys are subjected to moderate or high temperatures. Names given to the phenomena causing loss in properties include 475°C, sigma phase, and high-temperature embrittlement. This publication summarizes the literature describing the causes, the cures, and the limitations imposed on alloys when these problems occur. The most seriously limiting problem—high temperature embrittlement and loss or corrosion resistance—is discussed in considerable detail. The key role that interstitial carbon and nitrogen play on notch sensitivity and loss of ductility and corrosion resistance following a high-temperature exposure as in welding is defined. Good aswelded properties, the absence of which has severely restricted the use of ferritic stainless steels, depend on controlling interstitial carbon and nitrogen. The publication describes three methods that are being used for interstitial control. It is now possible to produce ferritic stainless steels which are tough and which have excellent corrosion resistance and ductility in the as-welded conditions. Several new high-chromium ferritic alloys with these desirable properties are being produced commercially.
ferritic stainless steels, embrittlement, sigma phase, properties, corrosion resistance, notch sensitivity, interstitial, stabilization
Paper ID: STP26972S