scholarly journals Thermal Fatigue Characteristics of Type 309 Austenitic Stainless Steel for Automotive Manifolds

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 129 ◽  
Author(s):  
Jianming Zhan ◽  
Moucheng Li ◽  
Junxia Huang ◽  
Hongyun Bi ◽  
Qian Li ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Fatigue Failure ◽  
Thermal Fatigue ◽  
Fatigue Behavior ◽  
Synergetic Effect ◽  
Maximum Temperature ◽  
Void Coalescence ◽  
Temperature Oxidation ◽  
Maximum Temperatures

The thermal fatigue behavior of type 309 austenitic stainless steel was investigated by cyclic tests ranged from 100 °C to the maximum temperatures 800 and 900 °C. The microstructures of the specimens were characterized by optical microscope, scanning electron microscope and X-ray diffraction. With changing the maximum temperature from 800 to 900 °C, the stainless steel exhibits much lower strength, higher elongation and a decrease of fatigue life about 56.6%. After the thermal fatigue failure, the specimens show micro-void coalescence fractures caused by the creep during the holding period at the maximum temperatures, and the quasi-cleavage feature also appears in the case of the maximum temperature 800 °C. During the thermal fatigue processes, the cavities usually form at the grain and twin boundaries, facilitating the initiation and growth of cracks. Furthermore, the high-temperature oxidation produces oxides on the specimen surfaces and in the cracks, deteriorating thermal fatigue properties. With an increase in the maximum temperature, the enhanced synergetic effect of strength, grain size, creep and oxidation is responsible for the accelerated fatigue failure of 309 stainless steel during the thermal cycles.

Effects of Surface Finish and Loading Conditions on the Low Cycle Fatigue Behavior of Austenitic Stainless Steel in PWR Environment for Various Strain Amplitude Levels

2009 ◽  
Author(s):  
Jean Alain Le Duff ◽  
Andre´ Lefranc¸ois ◽  
Jean Philippe Vernot
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Strain Amplitude ◽  
Surface Finish ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Complex Loading ◽  
Loading Conditions ◽  
Test Results ◽  
Cycle Fatigue

In February/March 2007, The NRC issued Regulatory Guide “RG1.207” and Argonne National Laboratory issued NUREG/CR-6909 that is now applicable in the US for evaluations of PWR environmental effects in fatigue analyses of new reactor components. In order to assess the conservativeness of the application of this NUREG report, Low Cycle Fatigue (LCF) tests were performed by AREVA NP on austenitic stainless steel specimens in a PWR environment. The selected material exhibits in air environment a fatigue behavior consistent with the ANL reference “air” mean curve, as published in NUREG/CR-6909. LCF tests in a PWR environment were performed at various strain amplitude levels (± 0.6% or ± 0.3%) for two loading conditions corresponding to a simple or to a complex strain rate history. The simple loading condition is a fully reverse triangle signal (for comparison purposes with tests performed by other laboratories with the same loading conditions) and the complex signal simulates the strain variation for an actual typical PWR thermal transient. In addition, two various surface finish conditions were tested: polished and ground. This paper presents the comparisons of penalty factors, as observed experimentally, with penalty factors evaluated using ANL formulations (considering the strain integral method for complex loading), and on the other, the comparison of the actual fatigue life of the specimen with the fatigue life predicted through the NUREG report application. For the two strain amplitudes of ± 0.6% and ± 0.3%, LCF tests results obtained on austenitic stainless steel specimens in PWR environment with triangle waveforms at constant low strain rates give “Fen” penalty factors close to those estimated using the ANL formulation (NUREG/6909). However, for the lower strain amplitude level and a triangle loading signal, the ANL formulation is pessimistic compared to the AREVA NP test results obtained for polished specimens. Finally, it was observed that constant amplitude LCF test results obtained on ground specimens under complex loading simulating an actual sequence of a cold and hot thermal shock exhibits lower combined environmental and surface finish effects when compared to the penalty factors estimated on the basis of the ANL formulations. It appears that the application of the NUREG/CR-6909 in conjunction with the Fen model proposed by ANL for austenitic stainless steel provides excessive margins, whereas the current ASME approach seems sufficient to cover significant environmental effects for representative loadings and surface finish conditions of reactor components.

An Experimental and Numerical Methodology to Investigate Crack Growth in a 304L Austenitic Stainless Steel Pipe Under Thermal Fatigue

2010 ◽  
Author(s):  
Pauline Bouin ◽  
Antoine Fissolo ◽  
Ce´dric Gourdin
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Growth ◽  
Thermal Fatigue ◽  
Thermal Loading ◽  
Steel Pipe ◽  
Design Stage ◽  
Inner Surface ◽  
Stainless Steel Pipe

This paper covers work carried out by the French Atomic Energy Commission (CEA) to investigate on mechanisms leading to cracking of piping as a result of thermal loading existing in flow mixing zones. The main purpose of this work is to analyse, with a new experiment and its numerical interpretation, and to understand the mechanism of propagation of cracks in such components. To address this issue, a new specimen has been developed on the basis of the Fat3D experiment. This thermal fatigue test consists in heating a 304L steel pre-cracked tube while cyclically injecting ambient water onto its inner surface. The tube is regularly removed from the furnace for a crack characterisation. Finally, the crack growth is evaluated from the crack length differences between two stops. In parallel, a finite element analysis is developed using the finite element Cast3M code. A pipe with a semi-elliptical crack on its inner surface is modelled. A cyclic thermal loading is imposed on the tube. This loading is in agreement with experimental data. The crack propagates through the thickness. A prediction of the velocity of the crack is finally assessed using a Paris’ law type criteria. Finally, this combined experimental and numerical work on 304L austenitic stainless steel pipes will enable to improve existing methods to accurately predict the crack growth under cyclic thermal loadings in austenitic stainless steel pipe at the design stage.

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