Distortion and residual stresses in electron beam-welded hydroelectric turbine materials

Sarafan, Sheida; Lévesque, Jean-Benoît; Wanjara, P.; Gholipour, Javad; Champliaud, Henri

doi:10.1080/13621718.2015.1132127

Cited by 10 publications

(7 citation statements)

References 19 publications

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“…is volumetric expansion then contributes significantly towards the development of compressive residual stresses and can compensate for the tensile residual stress transpiring from the accumulated thermal contraction strains due to EBW [38]. As the authors observed previously for as-welded CA6NM [11], the core FZ region in the heavy section weld can thus develop very high compressive residual stresses (− 500 MPa) relative to the HAZ that experiences high tensile residual stresses (600 MPa). During PWHT, stress relaxation mechanisms [39] reduce both the compressive and tensile residual stresses in the CA6NM EB weld.…”

Section: Residual Stress Distribution In Eb Welded Ca6nm Aftermentioning

confidence: 52%

“…e mechanical performance data generated for both materials indicated that the welds exhibited high strength and toughness [9,10] without PWHT. However, the residual stresses after EBW (∼600 MPa) CA6NM [11] were 110% of the YS of the alloy and greater than that recommended to prevent the initiation of unstable/premature failure. us, understanding the role of PWHT on the characteristics and properties of CA6NM EB welds is crucial for comprehensive assessment of the process feasibility to guide industrial practice for manufacturing low-carbon 13% Cr-4% Ni martensitic stainless steels.…”

Section: Introductionmentioning

confidence: 79%

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Through‐Thickness Residual Stresses, Microstructure, and Mechanical Properties of Electron Beam‐Welded CA6NM Martensitic Stainless Steel after Postweld Heat Treatment

Sarafan

Wanjara

Lévesque

et al. 2020

Advances in Materials Science and Engineering

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In this study, the integrity of electron beam- (EB-) welded CA6NM—a grade of 13% Cr-4% Ni martensitic stainless steel—was assessed through the entire joint thickness of 90 mm after postweld heat treatment (PWHT). The joints were characterized by examining the microstructure, residual stresses, global mechanical properties (static tensile, Charpy impact, and bend), and local properties (yield strength and strain at fracture) in the metallurgically modified regions of the EB welds. The applied PWHT tempered the “fresh” martensite present in the microstructure after welding, which reduced sufficiently the hardness (<280 HV) and residual stresses (<100 MPa) to meet the requirements for hydroelectric turbine assemblies. Also, the properties of the EB joints after PWHT passed the minimum acceptance criteria specified in ASME sections VIII and IX. Specifically, measurement of the global tensile properties indicated that the tensile strengths of the EB welds in the transverse and longitudinal directions were on the same order as that of the base metal (BM). Evaluation of the local tensile properties using a digital image correlation (DIC) methodology showed higher local yield strengths in the fusion zone (FZ) and heat-affected zone (HAZ) of 727 MPa and 740 MPa, respectively, relative to the BM value of 663 MPa. Also, the average impact energies for the FZ and HAZ were 63 J and 148 J, respectively, and attributed to the different failure mechanisms in the HAZ (dimples) versus the FZ (quasi-cleavage consisting of facets and dimples). This study shows that the application of PWHT plays an important role in improving the weld quality and performance of EB-welded CA6NM and provides the essential data for validating the design and manufacturing process for next-generation hydroelectric turbine products.

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Section: Residual Stress Distribution In Eb Welded Ca6nm Aftermentioning

confidence: 52%

Section: Introductionmentioning

confidence: 79%

Through‐Thickness Residual Stresses, Microstructure, and Mechanical Properties of Electron Beam‐Welded CA6NM Martensitic Stainless Steel after Postweld Heat Treatment

Sarafan

Wanjara

Lévesque

et al. 2020

Advances in Materials Science and Engineering

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“…The slitting method (Cheng and Finnie, 2007;Hill, 2013;Lee and Hill, 2007) was used to measure the thickness-averaged circumferential stress on a plane along the rolling direction (Pagliaro, 2008). A cross-sectional map of residual circumferential stress was measured on a plane along the transverse direction using the contour method (Hill and Olson, 2014;Hosseinzadeh and Bouchard, 2013;Kartal et al, 2016;Prime and DeWald, 2013;Sarafan et al, 2016;Withers et al, 2008;Xie et al, 2015;Zhang et al, 2003;Zhang et al, 2015), and the details for this specimen have been reported previously (Pagliaro et al, 2011). After the contour measurements, the radial stresses were measured on the exposed surface using x-ray diffraction and hole drilling, and superposition was…”

Section: Residual Stress and Strain Measurementsmentioning

confidence: 99%

Amplified effect of mild plastic anisotropy on residual stress and strain anisotropy

Prime

2017

International Journal of Solids and Structures

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Highlights Axisymmetric indentation produced residual stresses in a disk of 2024 Aluminum  Mild plastic anisotropy caused severe anisotropy in residual stress and strain  Modeling showed that constraint effects caused the amplified stress anisotropy  Hookean elasticity explained the even more amplified residual strain anisotropy AbstractAxisymmetric indentation of a geometrically axisymmetric disk produced residual stresses by non-uniform plastic deformation. The 2024 aluminum plate used to make the disk exhibited mild plastic anisotropy with about 10% lower strength in the transverse direction compared to the rolling and through-thickness directions. Residual stresses and strains in the disk were measured with neutron diffraction, slitting, the contour method, xray diffraction and hole drilling. Surprisingly, the residual-stress anisotropy measured in the disk was about 40%, the residual-strain anisotropy was an impressive 100%, and the residual stresses were higher in the weaker direction. The high residual stress anisotropy relative to the mild plastic anisotropy and the direction of the highest stress is explained by considering the mechanics of indentation: constraint on deformation provided by the material surrounding the indentation and preferential deformation in the most compliant direction for incremental deformation. By contrast, the much larger anisotropy in residual strain compared to that in residual stress is independent of the fabrication process and is instead explained by considering Hookean elasticity. For Poisson's ratio of 1/3, the relationship simplifies to the residual strain anisotropy equaling the square of the residual stress anisotropy, which matches the observed results (2 ≈ 1.4^2). A lesson from this study is that to accurately predict residual stresses and strains, one must be wary of seemingly reasonable simplifying assumptions such as neglecting mild plastic anisotropy.

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“…Figure 10 shows a schematic of Goldak's model with its geometrical parameters: a and b for the lateral extent of the ellipsoid and its penetration depth, whereas c f and c r are the front and rear extents of the semi-ellipsoids, respectively. Equations [22] and [23] give the power density within the double-ellipsoid. [43]…”

Section: A Finite Element Model and Simulation Parametersmentioning

confidence: 99%

“…A volumetric expansion is associated with this transformation which induces compressive residual stresses. [20][21][22][23] Most studies on residual stress calculation in materials subjected to martensitic transformation during welding found in the literature [24][25][26][27] use the Koistinen-Marburger [28] (K-M) relation to address the austenite to martensite phase transformation problem. Since then, subsequently derived models have been proposed within the same framework.…”

Section: Introductionmentioning

confidence: 99%

Modeling Solid-State Phase Transformations of 13Cr-4Ni Steels in Welding Heat-Affected Zone

Lévesque

Lanteigne

Champliaud

et al. 2019

Metall Mater Trans A

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Fatigue damage is commonly encountered by operators of Francis type hydraulic turbine runners made of 13Cr-4Ni soft martensitic stainless steel. These large and complex welded casting assemblies are subjected to fatigue crack initiation and growth in the vicinity of their welded regions. It is well known that fatigue behavior is influenced by residual stresses and the microstructure. By including solid-state phase transformation models in welding simulations, phase distribution can be evaluated along with their respective volumetric change and their effect on residual stresses. Thus, it enables the assessment of welding process on fatigue crack behavior by numerical methods. This paper focuses on modeling solid-state phase transformations of 13Cr-4Ni soft martensitic stainless steel, used for manufacturing hydraulic turbine runners, occurring upon welding. It proposes to determine the material parameters of the models for both the austenitic and the martensitic transformation by nonisothermal dilatometry tests. The experiments are conducted in a quenching dilatometer with applied thermal conditions as experienced in the heat-affected zone of homogeneous welds. The activation energy and the kinetic parameters of the austenitic transformation from fully martensitic state are measured from the experimental results. The martensitic transformation modeling from a fully austenitic domain is also presented.

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Distortion and residual stresses in electron beam-welded hydroelectric turbine materials

Cited by 10 publications

References 19 publications

Through‐Thickness Residual Stresses, Microstructure, and Mechanical Properties of Electron Beam‐Welded CA6NM Martensitic Stainless Steel after Postweld Heat Treatment

Through‐Thickness Residual Stresses, Microstructure, and Mechanical Properties of Electron Beam‐Welded CA6NM Martensitic Stainless Steel after Postweld Heat Treatment

Amplified effect of mild plastic anisotropy on residual stress and strain anisotropy

Modeling Solid-State Phase Transformations of 13Cr-4Ni Steels in Welding Heat-Affected Zone

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