Abstract
In this paper an experimental work is done for investigation of high temperature fracture properties of A286 superalloy at 650°C. Stress intensity factor K and parameter C* for this superalloy are determined experimentally. For estimation of these parameters, an instrument is developed for investigation of high temperature fracture properties. For estimation of stress intensity factor, compliance method is used. For this purpose four different compact tension specimens are tested and the parameter K is estimated. Creep tests are done for the selected specimens and parameter C* is determined by semiempirical relationships at 650°C. In these tests it is concluded that the specimens are placed near the plane stress condition. Crack growth behavior of this alloy is also studied. High incubation time (600 h) leads to overaging and therefore this alloy after this time showed very ductile creep properties, and fast creep crack growth was the major result of this overaging phenomenon. Finally the obtained results are compared with well-known nonexperimental methods for determination of these parameters. The obtained results showed that the results are in good agreement with each other.
Highlights
A286 alloy is an iron-base superalloy used in gas turbine jet engines, superchargers and in various applications at moderately elevated temperatures such as turbine wheels and blades, frames, casings, afterburner parts and fasteners
A286 alloy must be used at temperatures below that critical temperature to prevent from overaging process [1, 2]
In [2] the precipitation-hardened alloy A286 has been characterized as a function of ageing treatment, and the creep behavior has been studied in the temperature range of 600700°C and at 230740 MPa
Summary
A286 alloy is an iron-base superalloy used in gas turbine jet engines, superchargers and in various applications at moderately elevated temperatures such as turbine wheels and blades, frames, casings, afterburner parts and fasteners This alloy is strengthened by the ordered fcc γ′-Ni3(Al, Ti) precipitates that are coherent with the austenite matrix and are formed during ageing at 730°C. This alloy exhibits good mechanical properties, i.e., flow stress, at service conditions as well as at room temperature, and good corrosion resistance due to the elevated chromium content.
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