INCONEL® alloy MA 758 is an oxide-dispersionstrengthened (ODS) nickel-chromium superalloy, made by mechanical alloying. It is a development of the wellestablished aerospace superalloy, INCONEL alloy MA 754, with its chromium content increased to 30%, to improve its performance in corrosive environments at high temperatures. The alloy’s high-temperature strength is enhanced by the use of yttrium oxide for dispersion strengthening. In addition to its strength and corrosion resistance at high service temperatures, it is readily fabricated and can be hot formed into a range of shaped components for use in thermal processing applications. INCONEL alloy MA 758 is used in some of the most demanding applications for high-temperature metals and alloys. For example, for furnace skid rails to transport heavy steel billets and slabs, at 1260°C (2300°F) and above, and for the bowl-shaped components used to spin molten glass, at around 1200°C (2200°F), to produce fiberglass for thermal insulation. It is used in a range of thermal processing applications, from furnace components, such as hearth rollers, to jigs, tools, and other fabrications for supporting workpieces through heat-treatment processes. It has been specified for a fuel atomizer application in diesel engines. Publication No. SMC-075 Copyright © Special Metals Corporation 2004 (Sept 04) INCONEL® and INCOLOY® are trademarks of the Special Metals Corporation group of companies. The data contained in this publication is for informational purposes only and may be revised at any time without prior notice. The data is believed to be accurate and reliable, but Special Metals makes no representation or warranty of any kind (express or implied) and assumes no liability with respect to the accuracy or completeness of the information contained herein. Although the data is believed to be representative of the product, the actual characteristics or performance of the product may vary from what is shown in this publication. Nothing contained in this publication should be construed as guaranteeing the product for a particular use or application. Table 1 - Nominal Composition (wt.%) Chromium ............................................................................30.0 Carbon.................................................................................0.05 Aluminum...............................................................................0.3 Titanium.................................................................................0.5 Yttrium oxide (Y2O3)..............................................................0.6 Iron.........................................................................................1.0 Nickel............................................................................Balance* Mechanical alloying, the process used to produce INCONEL alloy MA 758, is a dry, high-energy ball milling operation that produces composite metal powders with controlled, extremely fine, microstructures. Typically, a mixture of commercially available metal powders, master alloy powders, and a very fine refractory oxide powder (Y2O3 for INCONEL alloy MA 758) is charged into the mill. During the process, metal powder particles are trapped between the rapidly colliding grinding balls and, under the controlled conditions of mechanical alloying, are cold-welded together. The oxide powder particles are trapped within the composite powders along the weld interfaces between the different composite constituents. The cold-welding leads to the build-up of larger powder particles. This is followed by a fracturing stage in which the larger composite powder particles are broken down. A balance is achieved between the welding and the fracturing so that the overall particle size of the composite powder remains nearly constant. The interplay between the welding and fracturing subdivides and kneads the ingredients to create a uniform distribution of the oxide and other metallic components.  Mechanically alloyed powders are consolidated by placing them in sealed cans for extrusion or hot pressing, followed by conventional hot- and coldworking processes. A final anneal at very high temperatures is required to develop the stable, coarse, grain structure suitable for the most demanding stressrupture applications. Made by Mechanical Alloying *Reference to the ‘balance’ of an alloy’s composition does not guarantee this is exclusively of the element mentioned, but that it predominates and others are present only in minimal quantities.