Chester T. Sims

A contemporary view of nickel-base superalloys

Nickel-base alloys, as designed for gas turbine use, have reached an interesting new level of technology. Where previously the main thrust of effort had been to improve mechanical capability, the problems of alloy phase stability and hot corrosion now control much alloy development, principally because of the need for increased alloy life and because gas turbines are being used in a wide variety of ambients. Fundamental and applied studies of hot corrosion phenomena are beginning to allow understanding and progress towards solution of the problem. Sodium sulfate has been the key reactant in the case of nickel alloys. Chromium, as an alloying element, helps inhibit hot corrosion, while molybdenum and aluminum appear to be a problem.

The Case for Chromium

Chromium, as an alloy base for high-temperature construction service, is discussed. The expectations for the metal and its technological limitations are approached from an historical point-of-view, and recent developments in chromium technology are discussed. In addition to the physical and strength properties of the metal, processing techniques, availability, and cost are discussed. The future prospects for this metal in high-temperature service are reviewed.

Metallurgy of Heat-Resisting Alloys

The following article is a summary of a one-day symposium held by the High-Temperature Alloys Committee of IMD at the 97th Annual Meeting of AIME in New York City, February 1968. At this February 28 Symposium, 12 papers were presented, spanning the spectrum of recent superalloy progress and development.

The High Temperature Properties of Mar-M Alloy 509

Mar-M alloy 509 is a contemporary Co-base alloy intended for constructional use in a corrosive environment at high temperature. This paper is the result of a continuing investigation to evaluate mechanical, process and physical parameters of this alloy system. The alloy exhibits low room-temperature ductility; heat treatments can improve ductility but will reduce rupture life at moderate stress and temperature (25ksi, 1600°F.) Mar-M alloy 509 exhibits good oxidation resistance to 1900°F and excellent hot-corrosion resistance at 1600°F. The flat negative slope of the Mar-M alloy 509 stress-rupture curve also indicates a high degree of phase stability.

Oxidation Behavior and Protection Of Refractory Metals

Abstract Relative oxidation behavior and degree to which oxide properties affect the oxidation resistance of columbium, tantalum, molybdenum, tungsten and rhenium are presented. Recent work in development of oxidation-resistant columbium and tantalum alloys is reviewed and the current status of protection of molybdenum by cladding and coating discussed. 6.5