High Strength Nickel-Chromium-Molybdenum Microcrystalline Alloy via Rapid Solidification Technology (RST)
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HIGH STRENGTH NICKEL-CHROMIUM-MOLYBDENUM MICROCRYSTALLINE ALLOY VIA RAPID SOLIDIFICATION TECHNOLOGY (RST) V. PANCHANATHAN Marko Materials, North Billerica,
Inc.. 144 Rangeway Road, MA 01862
ABSTRACT There is a growing national need for development of new improved materials having superior corrosion resistance combined with high mechanical strength. This paper discusses the properties and corrosion behavior of a new nickel-chromium-molybdenum microcrystalline alloy made via rapid solidification powder process, making it suitable for potential applications in corrosive environments. The alloy, called Markomet* 1119, has the following composition in weight percent: Bal Ni, 20.3Cr, 22.8Mo, 2.9Fe, 0.5B, 0.8C. This is prepared as rapidly solidified powder by the method of a melt-spinning-pulverization process. The powder is consoldated into rods by hot extrusion. The mechanical properties and corrosion tests carried out on Markomet 1119 are reported. The microstructural feature of the alloy as investigated by SEM is also reported. INTRODUCTION Rapid solidification technology (RST) has been recognized in recent years as having excellent prospects for creation of new engineering alloys with improved service performance characteristics [1-3]. The major research and development efforts on RST alloys in the past several years have been geared towards enhancement of mechanical properties for structural applications. One field where RST can make a significant contribution is in the development of new alloys having high corrosion resistance combined with superior mechanical strength [4-6]. These improvements in corrosion resistance and mechanical properties are expected to result from one or more of the following characteristics of these rapidly quenched materials: (a) unique chemical compositions and novel ultrafine grained microstructures, and (b) excellent chemical homogeneity and uniformity of structures. Marko Materials recently carried out a research program with the objective of developing a new RST nickel-base alloy combining high strength and superior corrosion resistance. Some results of this investigation are reported in this paper. Experimental Procedures Alloy Composition In
the present investigation a nickel-base alloy, designated
*Markomet is
the Registered Trademark of Marko Materials,
Mat. Res.Soc. Symp.Proc. Vol. 28 (1984) Published by Elsevier Science Publishing Co.,Inc.
Inc.
408
as Markomet 1119, of the following composition was used: Bal Ni, 20.3Cr, 22.8Mo, 2.9Fe, 0.5B, and 0.8C. The alloy contains as primary constituents chromium for oxidation resistance and molybdenum for pitting resistance. Additionally it contains low, yet critical amounts of carbon and boron necessary for the formation of metallic glass upon rapid solidification. Processing The nickel-base alloy (Markomet 1119) was prepared as ingot by induction melting of constituent elements of maxium practical purity. The alloy was rapidly solidified as brittle ribbons (with thicknesses of 25-75 microns) by the RST technique of melt spinnin
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