Creep Rupture Life of Pre-Strained Superalloy N07080 (original) (raw)
Related papers
2008
Uniaxial cylindrical compression tests at various temperatures and strain rates have been performed on the Nimonic 80A superalloy samples in order to define the best hot working characteristics. Evolution of the microstructure in correlation to the deformation temperatures, strain and strain rates has also been investigated by means of optical microscopy. The activation energy for hot deformation was derived with use of the Zener-Hollomon hyperbolic sine equation. Onset of dynamic recrystallization (DRX) was investigated with interrupted compression tests and metallographic analysis. Experimental data was also used for calculation of the processing maps on the basis of Dynamic Material Model. Izvleček: Pri študiji najprimernejših karakteristik vroče predelave superzlitine Nimonic 80 A so bili izvedeni enoosni valjasti tlačni preizkusi pri različnih temperaturah in hitrostih deformacije. Razvoj mikrostrukture v odvisnosti od temperature deformacije, deformacije in hitrosti deformacije je bila raziskana z optično mikroskopijo. Aktivacijska energija za deformacijo je bila izračunana s pomočjo sinushiperbolične oblike Zener-Hollomonove enačbe. Začetek dinamične rekristalizacije je bil raziskan s prekinjenimi tlačnimi preizkusi in metalografsko analizo. Podatki dobljeni s preizkusi so služili tudi izračunu procesnih map.
Variations in overall-and phase-hardness of a new Ni-based superalloy during isothermal aging
Influence of isothermal aging on the microstructures and hardness in Inconel 740, a relatively new Nibased superalloy, was explored using the specimens aged at 810 • C for different times. As aging time increased, the size of gamma prime precipitates continuously increased while their fraction remained almost constant. Nanoindentation experiments revealed that the overall hardness increased till the aging time of 100 h and then decreased with the aging time. Estimation of phase hardness by applying a simple rule-of-mixture showed that, with aging time, the hardness of gamma matrix decreased whereas that of gamma prime precipitates increased. The aging-induced strength change is discussed in terms of the possible contributions of precipitation strengthening and solid solution strengthening.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009
This work studied the effect of grain size evolution of cold drawn 0.12wt% C steel subjected to process annealing on tensile behavior. 20%, 25%, 40% and 55% cold drawn 0.12wt% C steel were subjected to annealing comprising of slow heating-up to various temperature ranging from 500oC to 700oC at interval of 50oC followed by soaking treatment for 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes under each of the temperature in a muffle furnace. These samples were submitted tooptical microscopy analysis and to tensile test. After annealing at 650oC and soaked for 10 minutes, the dislocation defects were annihilated in the 25% cold drawn samples. Grain coarsening is observed for the annealed steel at soaking time of 20 minutes to 30 minutes after which grain growth commenced at annealing temperature above 650oC at soaking time of 40 minutes for the 25%, 40% and 55% cold drawn samples. Fine grains of the microstructure were observed for all the annealed samples between the temperature range 500 o C-650 o C.The yield strength of the annealed samples increases compared to the non-treated samples thus improving the ductility of the steel. A better improvement of the yield strength is observed for the annealing temperature of 500 o C and 550 o C at soaking time of 10 minutes and 30 minutes for all the cold drawn samples except for the annealed 25% cold drawn steel whose yield strength is below the yield strength of the non-treated samples.
Creep straining micro-mechanisms in a powder-metallurgical nickel-based superalloy
Materials Science and Engineering: A, 2004
Polycrystalline NR3 nickel-based superalloy is a new-generation alloys produced by powder metallurgy for application as turbine disks of a future supersonic airplane. A special heat treatment is used to form a bimodal size distribution of ␥ precipitates. Post mortem transmission electron microscopy is used to observe dislocation structures obtained after creep around 700 • C and 650 MPa, up to 0.2% of plastic deformation. The deformation within a grain is heterogeneous and is principally due to the shearing of both types of precipitates by two different processes which where analysed. The smaller precipitates, called tertiary, are shown to play a major role in the hardening processes. In the proximity of serrated grain boundaries, where perfect dislocations are located, the deformation is higher, which is attributed to an enhanced internal stress in the middle of the grain.
Response to Hot Deformation Conditions and Microstructure Development of Nimonic 80A Superalloy
Materials and Manufacturing Processes, 2009
Laboratory compression tests at different temperatures and strain rates have been performed on Nimonic 80A superalloy to define optimal hot forming characteristics. A mathematical expression connecting mean grain size and true stress is presented using a Hall-Petch-like equation. The evolution of microstructure at various sample positions in correlation with deformation temperatures, strain, and strain rates has also been investigated. Optimal hot-working conditions are determined using processing maps and obtained microstucture.
Rejuvenation of creep resistance of a Ni-base single-crystal superalloy by hot isostatic pressing
Materials & Design, 2017
A single specimen is exposed to a creeprejuvenation-creep test cycle. • A hot isostatic press providing fast quenching rates is used for rejuvenation. • Microstructural evolution before and after creep as well as, rejuvenation are studied. • Focus is on the γ/γ′-microstructure, pores, dislocations, and recrystallization. • The impact of rejuvenation on additional creep life is evaluated.
High Temperature Degradation of Powder-processed Ni-based Superalloy
Materials Engineering Materialove Inžinierstvo, 2015
The aim of present work is to study the high temperature degradation of the powder-processed polycrystalline superalloy Ni-15Cr-18Co-4Al-3.5Ti-5Mo. This superalloy has been applied as material for grips of a creep machine. The material was exposed at 1100 °C for about 10 days at 10 MPa stress. During the creep test occurred unacceptable creep deformation of grips as well as severe surface oxidation with scales peeling off. Three types of the microstructure were observed in the studied alloy: (i) unexposed state; (ii) heat treated (annealing-10 min/ 1200 °C) and (iii) after using as a part of the equipment of the creep machine during the creep test. It is shown that the microstructure degradation resulting from the revealed γ´ phase fcc Ni 3 (Al,Ti) particles preferentially created at the grain boundaries of the samples after performing creep tests affects mechanical properties of the alloy and represents a significant contribution to all degradation processes affecting performance and service life of the creep machine grips. Based on investigation and obtained results, the given material is not recommended to be used for grips of creep machine at temperatures above 1000 °C.
Hot Deformation Behavior of a Ni-Based Superalloy with Suppressed Precipitation
2021
Inconel®718 is a well-known nickel-based super-alloy used for high-temperature applications after thermomechanical processes followed by heat treatments. This work describes the evolution of the microstructure and the stresses during hot deformation of a prototype alloy named IN718WP produced by powder metallurgy with similar chemical composition to the matrix of Inconel®718. Compression tests were performed by the thermomechanical simulator Gleeble®3800 in a temperature range from 900 to 1025 °C, and strain rates scaled from 0.001 to 10 s−1. Flow curves of IN718WP showed similar features to those of Inconel®718. The relative stress softening of the IN718WP was comparable to standard alloy Inconel®718 for the highest strain rates. Large stress softening at low strain rates may be related to two phenomena: the fast recrystallization rate, and the coarsening of micropores driven by diffusion. Dynamic recrystallization grade and grain size were quantified using metallography. The recry...
Materials Science and Engineering, 1979
The effects of isothermal aging in the temperature range 1023 -1123 K on the 7' phase in the nickel-base superalloy IN-738 have been studied both with and without an applied creep stress. The initial heat treatment produces a bimodal distribution of small spheroidal precipitates (about 0.05 pm radius) and larger cuboidal precipitates (about 0.5 pm radius). During aging both types of precipitate obey diffusion-controlled coarsening kinetics (Ostwald ripening) but the cuboids coarsen at the expense of the spheroids until the latter eventually disappear. These microstructural changes are reflected by a decrease in room temperature hardness and a loss of creep resistance. It is demonstrated that at 1123 K the creep strength falls rapidly during about the first 5 × 106 s of aging. At 1023 K the coarsening of the 7' precipitates is much slower, but their importance is illustrated by the loss in creep resistance resulting from intermediate overaging heat treatments. However, it is shown that the creep strength at this temperature can subsequently be restored using a regenerative heat treatment. These results are discussed in the light of classical theories of creep of dispersion-hardened alloys.
Philosophical Magazine Letters, 2010
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