Abstract. ATI 718Plus® is a nickel-base superalloy designed to promote resistance and thermal stability at elevated temperatures. Beside these properties, this material presents superior formability during forging operations, making ATI 718Plus® a suitable material for the manufacture of non-rotating and rotating components for jet engine and land-based turbines. Present contribution summarizes main results when several contoured rings were produced by ringrolling processes considering selected parameters as temperature and deformation ratio. Effect of solution and precipitation heat treatments on ATI 718Plus® microstructure and mechanical properties are also reported. These results include tensile testing at elevated temperature and stressrupture testing. Microstructural evaluations performed by optical microscopy and electronic microscopy, complement reported results.
Hot rolled rings made from nickel-based superalloys are used for the manufacture of rotating components in jet engines and land-based turbines. Contoured rings are attractive to manufacturers because they can simplify and improve manufacturing operations by reducing machining times and, in some cases, eliminating welding operations. ATI 718Plus is a nickel-based superalloy designed to achieve high strength and thermal stability at elevated temperatures while exhibiting good formability during forging operations, characteristics that making it a suitable alloy for the manufacture of contoured rings. This work presents the results of a series of solution and precipitation heat treatments of rings made from ATI 718Plus with the goal of optimizing their processing and mechanical behavior. Microstructural characteristics and mechanical properties are reported, including the results of tensile tests conducted at room temperature and at high temperature and of hardness and stress-rupture testing. The results of this work were implemented at a local factory to ensure the required mechanical properties of heat-treated parts.
Haynes HR-120 alloy (UNS N08120) is a nickel–iron–chromium alloy that exhibits high strength at elevated temperature and resistance to carburising and sulphidising environments. These properties make this alloy suitable for the production of components of land based turbines, including rings. Manufacture and heat treating of such rings require strict control of the processing variables, such as temperature and deformation ratios, as well as the time and temperature of the solution treatment, due to their effect on microstructure and mechanical properties. It is common practice to treat this alloy at temperatures above 1100°C to promote dissolution of undesired particles and recrystallisation of deformed structures, but it has been found that grain coarsening can occur during treatment. The present work presents the results of a series of solution heat treatments that were performed within a broad range of temperatures on industrial ring rolled pieces. It was found that the increment in time and temperature enhances the dissolution of intergranular precipitates that result in the improvement of mechanical properties, but grain coarsening is observed to occur when the material is treated for long times and high temperatures. The best combination of mechanical properties and grain size was obtained by treating the material for half an hour at 1050°C.
Alloy 909 is a Ni–Fe–Co alloy that exhibits a low coefficient of thermal expansion and high strength at elevated temperatures. These characteristics are suitable for demanding high temperature uses such as turbine components for aerospace and energy generation. The mechanical properties are achieved by heat treatment (solution and aging) that affects the microstructural characteristics such as grain size and precipitation of intergranular and transgranular particles. This work summarises the results of trials conducted to determine the conditions that assure the desired mechanical properties in high temperature ring rolled pieces. Results of tensile, hardness and stress rupture tests are complemented by microstructural analyses. These studies allowed for establishing a robust method for the manufacture of rings; no degradation of the product, either metallurgical or due to properties, has been reported after the method was implemented.
Since their appearance during in the 1940 decade, nickel-base alloys are appreciated for their superior mechanical properties and microstructural stability at elevated temperatures and high stresses. They are typically used in jet-engines and land-based turbines for energy generation. Such materials, known as superalloys are in constant evolution as designers are encouraged to propose more efficient and powerful systems of propulsion and energy generation. This evolution leads to conceive and manufacture new superalloys capable to fulfill higher requirements. Alloy 718Plus® is emerging as an alternative material for the design and construction of components to be used in jet-engines and land-based turbines for energy generation. 718Plus® is a precipitation hardened nickel-base alloy designed to have the stability of superalloys similar to Waspaloy and the good processing characteristics of other materials as the 718 alloy. Since the early 2000 decade, ATI Allvac has lead a complete program in order to validate capabilities and properties of the 718Plus® alloy. Objectives for this effort include a characterization and its introduction as a viable material for the design and manufacture of components to be installed technologically. As part of this project, contoured rings made of 718Plus® are rolled considering industrial conditions. Several heat treatments, involving solution and precipitation processes are performed on segments extracted from involved contoured rings. Effects of such hot-working conditions and heat treatment procedures on properties as forgeability, tensile, hardness and stress-rupture characteristics are evaluated. Optical and electron microscopy are performed to evaluate microstructural properties as grain size and promotion of precipitates, in order to complement reported results.
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