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Article
Publication date: 13 March 2019

Guo Yi, Junhua Xu and Chuanbo Zheng

There are obvious differences in corrosion resistance of different 2205 welding joints with different ratios of austenite and ferrite, from the top to the bottom, the austenite…

162

Abstract

Purpose

There are obvious differences in corrosion resistance of different 2205 welding joints with different ratios of austenite and ferrite, from the top to the bottom, the austenite content decreased gradually while the ferrite increased. In each region of welded joint, the pitting resistance number of ferrite is higher than that of austenite; pitting corrosion is more likely to occur in austenite phase first on the top region of the weld and in the secondary phase precipitates on the other regions of the weld. The fluctuation of the ratio of austenite and ferrite has a great influence on performance of passive film in 3.5 per cent NaCl solution.

Design/methodology/approach

To study the corrosion behavior of welded joint, the samples were obtained by laser hybrid welding. Pitting corrosion was studied in different area of welded joint. The Mott–Schottky curves of welded joints were measured to study the passive film on the different welded joint area.

Findings

Due to the difference of heat input and the limit of filler depth of the wire, the microstructure of duplex stainless steel laser welding joint has obvious difference in the thickness direction. In addition, there will be harmful secondary phase (such as chromium nitride and σphase) precipitates in the lower part of the joint. For the welded joint, the corrosion resistance decreases with the increase in the difference of the microstructure. Pitting corrosion usually takes the two phases as the nucleation point and grows up. The surface of 2205 duplex stainless steel laser hybrid welding joint cannot form a complete passive film in 3.5 per cent NaCl solution, and the more the ratios of austenite and ferrite deviate from equilibrium position (50:50), the worse the performance of passive film is.

Originality/value

In this paper, the authors attempt to establish the correlation between the semiconductor electronic properties of passive film and the difference of microstructures and the component in a joint welded by laser hybrid welding. The effect of passive film on the corrosion resistance of the weld was further investigated.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 17 April 2020

Chuanbo Zheng, Jiayan Huang and Gua Yi

This paper aims to study the effect of current density of hydrogen charging on the semiconductor properties and pitting initiation of 2205 duplex stainless steel (DSS) passivation…

188

Abstract

Purpose

This paper aims to study the effect of current density of hydrogen charging on the semiconductor properties and pitting initiation of 2205 duplex stainless steel (DSS) passivation film.

Design/methodology/approach

In this work, the 2205 DSS is pre-hydrogenated and passivated. Then, the passivation film is tested by electrochemical impedance method, Mott–Schottky curve method and dynamic potential scanning method. The influences of hydrogen on the properties of the passivation film and the corrosion behavior of the matrix were studied by analyzing the curves obtained in the electrochemical test. The surface of the passivation film after pre-hydrogenation and anodic polarization was observed by using the ultra-depth three-dimensional microscopy and the scanning electron microscope. The integrity, density and corrosion morphology of the passivation film were studied and discussed.

Findings

With the increase of the hydrogen current density, the growth of the passivation film is hindered, the concentrations of donor and acceptor in the film are increased, the conductivity of the passivation film increases. In the anodic polarization, the dimensional passive current density increases with the increase of the hydrogen current density, and the pitting potential is reversed, the more likely the sample is pitting. In general, hydrogen hinders the formation of the passive film on duplex stainless steel, which increases the concentration of point defects in the passive film. Finally, the passive film is easy to crack and pitting.

Originality/value

The performance of passive film is an important condition to influence the corrosion behavior of stainless steel. However, little research has been done on the effects of hydrogen on the electrochemistry and pitting sensitivity of 2205 DSS passivation films. The effect of hydrogen on semiconductor properties and pitting initiation of 2205 DSS passivation film is needed to be investigated.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 18 August 2021

Chuanbo Zheng, Cheng Zhang, Xiao Yong Wang and Jie Gu

Duplex stainless steel is composed of equal amounts of austenite and ferrite, which has excellent corrosion resistance and strength. However, after the metal was welded, the ratio…

151

Abstract

Purpose

Duplex stainless steel is composed of equal amounts of austenite and ferrite, which has excellent corrosion resistance and strength. However, after the metal was welded, the ratio of austenite and ferrite in the joint is unbalanced, and secondary phase precipitates are produced, which is also an important cause of pitting corrosion in the joint.

Design/methodology/approach

This paper aims to study the mechanical and corrosion behavior of welded joints, by adjusting the welding parameters of laser hybrid welding, dual heat sources are used to weld 2205 duplex stainless steel. The two-phase content of different parts of the welded joint is measured to study the influence of the ratio of the two-phase on the mechanical and corrosion properties of the joint.

Findings

The ratio of austenite and ferrite in different welded joints has an obvious difference, and from top to bottom, the austenite content decreased gradually, and the ferrite content increased gradually. The harmful phases are precipitated in the middle and lower part of the joint. The strength of welded joints is slightly lower than that of base metal. At the same time, the fracture analysis shows that some ferrite phases are affected by the precipitate in the grain and produce quasi-cleavage fracture. The corrosion results show that the corrosion resistance of the welded joints is lower than that of the base metal, and the concentration of chloride ions affects the corrosion resistance.

Originality/value

In this paper, the authors use the influence of different welding processes on the two-phase ratio of the joint to further study the influence of the microstructure on the corrosion resistance and mechanical properties of the weld.

Details

Anti-Corrosion Methods and Materials, vol. 68 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 4 July 2016

Ping Jiang, Qi Zhou, Xinyu Shao, Ren Long and Hui Zhou

The purpose of this paper is to present a modified bi-level integrated system collaborative optimization (BLISCO) to avoid the non-separability of the original BLISCO. Besides, to…

216

Abstract

Purpose

The purpose of this paper is to present a modified bi-level integrated system collaborative optimization (BLISCO) to avoid the non-separability of the original BLISCO. Besides, to mitigate the computational burden caused by expensive simulation codes and employ both efficiently simplified and expensively detailed information in multidisciplinary design optimization (MDO), an effective framework combining variable fidelity metamodels (VFM) and modified BLISCO (MBLISCO) (VFM-MBLISCO) is proposed.

Design/methodology/approach

The concept of the quasi-separable MDO problems is introduced to limit range of applicability about the BLISCO method and then based on the quasi-separable MDO form, the modification of BLISCO method without any derivatives is presented to solve the problems of BLISCO. Besides, an effective framework combining VFM-MBLISCO is presented.

Findings

One mathematical problem conforms to the quasi-separable MDO form is tested and the overall results illustrate the feasibility and robustness of the MBLISCO. The design of a Small Waterplane Area Twin Hull catamaran demonstrates that the proposed VFM-MBLISCO framework is a feasible and efficient design methodology in support of design of engineering products.

Practical implications

The proposed approach exhibits great capability for MDO problems with tremendous computational costs.

Originality/value

A MBLISCO is proposed which can avoid the non-separability of the original BLISCO and an effective framework combining VFM-MBLISCO is presented to efficiently integrate the different fidelities information in MDO.

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