scholarly journals Brittle Fracture of Stainless Steel Dissimilar Metal Welds in the Upper Shelf of the Brittle-to-Ductile Transition Range

2020 ◽  
Author(s):  
G. Ben Salem ◽  
S. Chapuliot ◽  
A. Blouin ◽  
P. Bompard ◽  
C. Jacquemoud
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Brittle Fracture ◽  
Intergranular Fracture ◽  
Fracture Mechanism ◽  
Operating Conditions ◽  
Transition Range ◽  
Hard Layer ◽  
Brittle To Ductile Transition ◽  
Dissimilar Metal

Abstract Stainless steel dissimilar metal welds (SS DMW) are widely used within the French nuclear power plants where they connect the main components (pressure vessel, pressurizer, steam generator) made of low alloy ferritic steel to the primary circuit pipes made of austenitic stainless steel. Because of their heterogeneous microstructure and mechanical properties, these junctions are critical components for the structure integrity and their fracture resistance has to be demonstrated for all the nominal or accidental operating conditions. This work aims at building a model to evaluate the risk of brittle fracture of the SS DMW in the upper shelf of the brittle-to ductile transition range. The observation of the microstructures around the fusion line revealed a martensitic layer and a fully austenitic zone, which undergo an important carbides precipitation during the post-weld heat treatment and form a narrow hard layer of carburized martensite and austenite. Fracture toughness tests were then carried out on CT specimens in the brittle-to-ductile temperature range and helped identify the MA interface (between martensite and austenite) as the weakest region in the SS DMW because of an intergranular fracture mechanism initiated at the carbides-rich interface. This mechanism was consistently observed for specimens with fatigue precrack fronts in the hard layer. To model the brittle behavior of the MA interface, the stress distributions on the MA interface were calculated with FE numerical simulation of the fracture toughness tests and a 1D 3 parameters Weibull model based on a threshold stress and a threshold length was identified for the CT specimens. The temperature dependence of the model parameters was finally studied and the effect of temperature on the intergranular fracture mechanism of the MA interface was explored.

Brittle Fracture Analysis of a Dissimilar Metal Weld

2013 ◽  
Author(s):  
A. Blouin ◽  
S. Chapuliot ◽  
S. Marie ◽  
J. M. Bergheau ◽  
C. Niclaeys
Keyword(s):  
Brittle Fracture ◽  
Weld Joint ◽  
Threshold Stress ◽  
Base Alloy ◽  
Welding Process ◽  
Loading Conditions ◽  
Brittle To Ductile Transition ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Metal Weld

One important part of the integrity demonstration of large ferritic components is based on the demonstration that they could never undergo brittle fracture. Connections between a ferritic component and an austenitic piping (Dissimilar Metal Weld — DMW) have to respect these rules, in particular the Heat Affected Zone (HAZ) created by the welding process and which encounters a brittle-to-ductile transition. Within that frame, the case considered in this article is a Ni base alloy narrow gap weld joint between a ferritic pipe (A533 steel) and an austenitic pipe (316L stainless steel). The aim of the present study is to show that in the same loading conditions, the weld joint is less sensitive to the brittle fracture than the surrounding ferritic part of the component. That is to say that the demonstration should be focused on the ferritic base metal which is the weakest material. The bases of this study rely on a stress-based criterion developed by Chapuliot et al., using a threshold stress (σth) below which the cleavage cannot occur. This threshold stress can be used to define the brittle crack occurrence probability, which means it is possible to determine the highest loading conditions without any brittle fracture risk.

Fracture Toughness in the Ductile-Brittle Transition and Thermal Ageing Behavior of Decarburized Heat Affected Zone of Alloy 52 Dissimilar Metal Welds of Nuclear Components

2014 ◽  
Author(s):  
Pierre Joly ◽  
Miguel Yescas ◽  
Elisabeth Keim
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Alloy Steel ◽  
Heat Affected Zone ◽  
Power Plants ◽  
Base Alloy ◽  
Thermal Ageing ◽  
Low Alloy Steel ◽  
Dissimilar Metal ◽  
Brittle Transition

Dissimilar metal welds (DMW) are used in nuclear power plants between the nozzles of main components in low alloy steel and stainless steel pipes, or safe-ends connected to the main coolant line pipes. AREVA proposes for EPR™ an improved design of DMW involving narrow gap welding without buttering between the low alloy steel nozzles and the stainless steel safe-ends, and the use of a corrosion resistant weld filler metal (Alloy 52). AREVA performed a thorough characterization of this type of welds, which shows a particular microstructure close to the fusion line between the low alloy steel and the nickel base alloy, where the heat affected zone of the low alloy steel is decarburized. This paper presents results of fracture toughness tests performed with the crack tip located in this area, in the ductile to brittle transition in the as post-welded heat treated condition and after thermal ageing. The results show an excellent fracture toughness behavior of this particular area, compared to that of low alloy steel parent metal.

NIROSTA 4438

Alloy Digest ◽  
2003 ◽  
Vol 52 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Physical Properties ◽  
Intergranular Corrosion ◽  
Heat Treating ◽  
Operating Conditions ◽  
Low Carbon ◽  
Corrosion Resistant

Abstract Nirosta 4438 is a molybdenum, 18-14 type austenitic stainless steel with higher molybdenum than most of the austenitic family of alloys. Due to its low carbon content, it is intergranular corrosion resistant under operating conditions up to 350 deg C (752 deg F). This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-879. Producer or source: ThyssenKrupp Nirosta GmbH.

scholarly journals Brittle fracture analysis of Dissimilar Metal Welds between low-alloy steel and stainless steel at low temperatures

2018 ◽  
Vol 13 ◽  
pp. 619-624
Author(s):  
Ghassen Ben Salem ◽  
Stéphane Chapuliot ◽  
Arnaud Blouin ◽  
Philippe Bompard ◽  
Clémentine Jacquemoud
Keyword(s):  
Stainless Steel ◽  
Brittle Fracture ◽  
Alloy Steel ◽  
Low Temperatures ◽  
Fracture Analysis ◽  
Low Alloy Steel ◽  
Dissimilar Metal

Dissimilar Metal Welds: Impact of the Residual Stresses on the Risk of Failure

2016 ◽  
Author(s):  
A. Blouin ◽  
S. Chapuliot ◽  
S. Marie
Keyword(s):  
Brittle Fracture ◽  
Residual Stresses ◽  
Weld Joint ◽  
Threshold Stress ◽  
Base Alloy ◽  
Welding Process ◽  
Loading Conditions ◽  
Brittle To Ductile Transition ◽  
Dissimilar Metal ◽  
Metal Weld

One important part of the integrity demonstration of large ferritic components is based on the demonstration that they could never undergo brittle fracture. Connections between a ferritic component and an austenitic piping (Dissimilar Metal Weld - DMW) have to respect these rules, in particular the Heat Affected Zone (HAZ) created by the welding process and which encounters a brittle-to-ductile transition. Within that frame, the case considered in this article is a Ni base alloy narrow gap weld joint between a ferritic pipe (A533 steel) and an austenitic pipe (316L stainless steel). The aim of the present study is to show that in the same loading conditions, the weld joint is less sensitive to the brittle fracture than the surrounding ferritic part of the component. That is to say that the demonstration should be focused on the ferritic base metal which is the weakest material. In addition, residual stresses are also considered and their impact on the fracture resistance is evaluated. The bases of this study rely on a stress-based criterion developed by Chapuliot et al, using a threshold stress (σth) below which the cleavage cannot occur. This threshold stress can be used to define the brittle crack occurrence probability, which means it is possible to determine the highest loading conditions without any brittle fracture risk.

Effects of yttria content and sintering temperature on the microstructure and tendency to brittle fracture of yttria-stabilized zirconia

2021 ◽  
Vol 2 (109) ◽  
pp. 65-79
Author(s):  
V.V. Kulyk ◽  
Z.A. Duriagina ◽  
B.D. Vasyliv ◽  
V. Vavrukh ◽  
T.M. Kovbasiuk ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Fracture Surface ◽  
Physical And Mechanical Properties ◽  
Ceramic Materials ◽  
Optical Microscope ◽  
Operating Conditions ◽  
Vickers Indentation ◽  
Indentation Method ◽  
Young’S Moduli

Purpose: The purpose of this work is to evaluate the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria, based on a study of changes in the microstructure, phase composition, and fracture micromechanisms. Design/methodology/approach: The series of 3YSZ, 4YSZ, and 5YSZ ceramic specimens were sintered in an argon atmosphere. Three sintering temperatures were used for each series: 1450°C, 1500°C, and 1550°C. Microhardness measurements were performed on a NOVOTEST TC-MKB1 microhardness tester. The configuration of the imprints and cracks formed was studied on an optical microscope Neophot-21. The fracture toughness of the material was estimated using both the Vickers indentation method and a single-edge notch beam (SENB) test performed under three-point bending at 20°C in air. The microstructure and morphology of the fracture surface of the specimens were studied using a scanning electron microscope Carl Zeiss EVO-40XVP. The chemical composition was determined using an INCA ENERGY 350 spectrometer. Findings: Peculiarities of changes in the microstructure, the morphology of specimens fracture surface, and mechanical characteristics of YSZ ceramic materials of different chemical and phase compositions sintered in a temperature range of 1450°C to 1550°C are found. Research limitations/implications: To study the actual behaviour of YSZ ceramic materials under operating conditions, it is necessary to evaluate their Young’s moduli, strength, microhardness, and fracture toughness in an operating environment of the corresponding parameters (temperature, pressure, etc.).Practical implications: Based on the developed approach to estimating the propensity to brittle fracture of the formed YSZ ceramic microstructure, it is possible to obtain YSZ ceramic material that will provide the necessary physical and mechanical properties of a wide variety of precision ceramic products. Originality/value: An approach to estimating the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria is proposed based on two methods of evaluating crack growth resistance of materials, namely, the Vickers indentation method and SENB method.

UNITEMP HX

Alloy Digest ◽  
1964 ◽  
Vol 13 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Base Material ◽  
Heat Treating ◽  
Operating Conditions ◽  
High Temperature Strength ◽  
Temperature Performance ◽  
Nickel Base

Abstract Unitemp-HX is a nickel-base material recommended for high temperature applications. It has outstanding oxidation resistance at high temperatures under most operating conditions, and good high-temperature strength. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-91. Producer or source: Universal Cyclops Steel Corporation.

WAUKESHA ALLOY 88

Alloy Digest ◽  
1993 ◽  
Vol 42 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
High Temperature ◽  
Physical Properties ◽  
Base Alloy ◽  
Heat Treating ◽  
Nickel Base Alloy ◽  
Corrosion Resistant ◽  
Temperature Performance ◽  
Nickel Base

Abstract WAUKESHA METAL NO. 88 is a corrosion resistant nickel-base alloy compounded to run against stainless steel without galling or seizing. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on high temperature performance as well as casting, heat treating, machining, and joining. Filing Code: Ni-84. Producer or source: Waukesha Foundry Company. Originally published July 1963, revised February 1993.

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