Étude de lÉndomagement en Fatigue Thermo-Mécanique de Superalliages à Base de Nickel (original) (raw)
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ON THERMAL FATIGUE OF NICKEL-BASED SUPERALLOYS
The thermal fatigue (TF) behaviour of two single crystal nickel-based super-alloys, SRR99 and CMSX-4, is reported. Single edge wedge specimens are rapidly heated by induction heating of the wedge tip to a maximum temperature between 1000~ and 1175~ and cooled to 200~ by forced air. A constant cycle period is employed for all experiments. The strain distribution along the edge of the TF specimens is measured. Changing the induction frequency leads to different strain ranges. CMSX-4 shows crack initiation always on cast microporosities. SRR99 presents an additional oxidation/spalling/re-oxidation mechanism under low strain loading. An "integrated approach" combining TF and TMF (thermo-mechanicai fatigue) is proposed. The applied TMF temperature-strain cycle is deduced from the measured TF-cycle. Under this new temperature-strain cycle the crack initiation life and the total life in TMF for SRR99 are compared with the TF results.
Engineering Failure Analysis, 2009
Low cycle fatigue, high cycle fatigue, fatigue crack propagation and thermo-mechanical fatigue in Ni-base superalloys are reviewed in terms of fundamental deformation mechanisms, environmental effects, and interactions between environment and deformation mode. These factors are related to the chemical composition and underlying microstructure for all currently-used product forms (i.e. powder metallurgy, wrought, conventionally cast and single crystal). The basic principles that are developed are used to show how both intrinsic and extrinsic variables can be manipulated to control fatigue behaviour and as a guide for formulation of engineering life prediction models.
Fatigue behavior in nickel-based superalloys: A literature review
JOM, 1997
Authors' Note: [nconeL [ncoloy, and Nicalon are regzstered trademarks. In this literature review, tl,e present understanding regarding the effects of microstructure, loading conditions, and environments on the fatigue behavior of nickel-based superalloys is reviewed.
Thermal-mechanical fatigue behavior of nickel-base superalloys
1986
The main achievements of a 36-month research program are presented. The main objective was to gain more insight into the problem of crack growth under thermal mechanical fatigue (TMF) conditions. This program was conducted at M.I.T. for the period of September 1982 to September 1985. The program was arranged into five technical tasks. Under Task I, the literature of TMF data was reviewed. The goal was to identify the crack propagation conditions in aircraft engines (hot section) and to assess the validity of conventional fracture mechanics parameters to address TMF crack growth. The second task defined the test facilities, test specimen and the testing conditions needed to establish the effectiveness of data correlation parameters identified in Task I. Three materials (Inconel X-750, Hastelloy-X, and B-1900) were chosen for the program. Task II was accomplished in collaboration with Pratt & Whitney Aircraft engineers. Under Task III, a computerized testing system to measure the TMF ...
The Effect of Temperature and Phase Shift on the Thermomechanical Fatigue of Nickel-Based Superalloy
Metals
In this paper, the minimum temperature and phase shift effects on the thermo–mechanical fatigue (TMF) behavior of Inconel 713LC are investigated. TMF tests were performed under 0° (in-phase-IP) and +180° (out-of-phase-OP) phase shifts between mechanical strain and temperature. Cylindrical specimens were cycled at constant mechanical strain amplitude with a strain ratio of Rε = −1. Tests were performed with temperature ranges of 300–900 °C and 500–900 °C. The heating and cooling rate was 5 °C/s. Fatigue hardening/softening curves and fatigue life data were assessed. Results show that out-of-phase loading was less damaging than in-phase loading. Scanning electron microscopy (SEM) examination of metallographic sections indicated that the life-reducing damage mechanism was intergranular cavitation under in-phase loading. Transmission electron microscopy (TEM) revealed honeycomb structures for IP loading. The plastic strain localization into persistent slip bands was typical for OP loadi...
article, 2020
The influence of a delay time at the maximum temperature on the number of cycles for the macrocrack initiation for two thermal loading programs was investigated for two single-crystal nickel-based superalloys VIN3 and ZhS32. An analytic approximation of a delay time influence was proposed. Comparison of computational results and analytic formula on the base of constitutive equations with the experimental data was performed for considered single-crystal superalloys and showed a good accuracy. Influence of several mechanical constants of nickel alloy on thermal fatigue strength is presented and discussed. The influence of crystallographic orientation of the corset sample on the thermal fatigue durability with delay times for various thermal loading programs and different single-crystal nickel superalloys was investigated. 1. Introduction Single-crystal nickel-based superalloys [1] are used for production of gas turbine engines (GTE) [2]. These materials have a pronounced anisotropy an...
Low cycle fatigue of a nickel based superalloy at high temperature: deformation microstructures
Materials Science and Engineering: A, 2001
The microstructural characteristics of a single crystalline nickel based superalloy (AM1) tested under high temperature fatigue at 950°C are reported. For repeated fatigue (Rε=0) through a range of cycle numbers N with imposed total strain amplitude Δεt, two main types of behaviour are found depending on N and Δεt. This allows a map of microstructures versus the number of cycles
Metallurgical instabilities during the high temperature low cycle fatigue of nickel-base superalloys
Materials Science and Engineering, 1983
In Waspaloy the 3,-~/' mismatch is very low, the volume fraction of ~,' is about 0.3 and, in this heat treatment, deformation proceeds by superdislocations shearing the 3" with subsequent formation of well-defined slip bands. In this heat treatment there are MC carbides in the matrix and no carbides were observed on grain or twin boundaries [7]. Figure 1 shows
High-cycle fatigue-life of the cast nickel base-superalloys in 738 LC and IN 939
Metallurgical Transactions A, 1982
The high cycle fatigue (HCF) properties of two cast nickel base-superalloys, IN 738 LC and IN 939, were investigated using both fracture mechanics samples and smooth specimens. The crack propagation behavior was studied in terms of linear fracture mechanics at RT and at 850 ~ In addition to the influence of temperature, the influences of frequency, mean stress, and environment (vacuum, air, sulfidizing atmosphere) were studied. At 850 ~ the fatigue thresholds were found to be higher in air than in vacuum. This could be explained by crack branching. The high scatter of fatigue crack propagation rates could be related also to this phenomenon. The S/N curves at 850 ~ can be predicted treating crack growth from casting pores as the predominant failure mechanism. At RT the same method is not as successful. The reason for this may be that crack growth laws measured on long, branched cracks are not applicable to short, unbranched cracks. At RT, no significant influence of frequency on S/N-curves and fatigue crack growth rates was observed for frequencies up to 20 kHz.