A critical review on dissimilar welds joint between martensitic and austenitic steel for power plant application

Laves phases with their comparably simple crystal structure are very common intermetallic phases and can be formed from element combinations all over the periodic table resulting in a huge number of known examples. Even though this type of phases is known for almost 100 years, and although a lot of information on stability, structure, and properties has accumulated especially during the last about 20 years, systematic evaluation and rationalization of this information in particular as a function of the involved elements is often lacking. It is one of the two main goals of this review to summarize the knowledge for some selected respective topics with a certain focus on non-stoichiometric, i.e., non-ideal Laves phases. The second, central goal of the review is to give a systematic overview about the role of Laves phases in all kinds of materials for functional and structural applications. There is a surprisingly broad range of successful utilization of Laves phases in functional applications comprising Laves phases as hydrogen storage material (Hydraloy), as magneto-mechanical sensors and actuators (Terfenol), or for wear- and corrosion-resistant coatings in corrosive atmospheres and at high temperatures (Tribaloy), to name but a few. Regarding structural applications, there is a renewed interest in using Laves phases for creep-strengthening of high-temperature steels and new respective alloy design concepts were developed and successfully tested. Apart from steels, Laves phases also occur in various other kinds of structural materials sometimes effectively improving properties, but often also acting in a detrimental way.

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Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

Microstructure and fatigue properties of fiber laser welded dissimilar joints between high strength low alloy and dual-phase steels

Role of evolving microstructure on the mechanical behaviour of P92 steel welded joint in as-welded and post weld heat treated state

Microstructural characterization of an SA508–309L/308L–316L domestic dissimilar metal welded safe-end joint

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Microstructure and mechanical properties of dissimilar materials joints between T92 martensitic and S304H austenitic steels

This paper reports the creep rupture behaviors of T92/HR3C dissimilar materials joints. HR3C austenitic steel is welded with T92 martensitic steel to obtain T92/HR3C dissimilar materials joints. After welding, creep test is carried out at 625 °C in the stress range 110–180 MPa. The rupture locations of creep specimens are examined by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the creep rupture mechanism of the joint is dependent on stress. When stresses ≥140 MPa, rupture location is at the T92 base material part and the connection of adjacent dimples results in transcrystalline fracture. For stresses 23 C 6 particles grown up as well as Laves phase ((Fe, Cr) 2 (W, Mo)) precipitation on grain boundaries leads to the creep cavities and intergranular fracture.

Microstructural analysis on creep properties of dissimilar materials joints between T92 martensitic and HR3C austenitic steels

Dissimilar steels welded joints, between ferritic steel and austenitic stainless steel, are always encountered in high-temperature components in power plants. As two new grade ferritic steel and austenitic stainless steel, T92 (9Cr0.5Mo2WVNb) and HR3C (TP310HCbN), exhibit superior heat strength at elevated temperatures and are increas- ingly applied in ultra-supercritical (USC) plants around the world, a complete assessment of the properties for T92/HR3C dissimilar steels welded joints is urgently required. In this paper, metallographic microstructures across the joint were inspected by optical mi- croscope. Particularly, the creep rupture test was conducted on joints under different load stresses at 625 ◦ C to analyse creep strength and predict their service lives, while their fractograph were observed under scanning electron microscope. Additionally, finite element method was employed to investigate residual stress distribution of joints. Results showed that the joints were qualified under USC conditions, and T92 base material was commonly the weakest part of them.

Assessment of creep rupture properties for dissimilar steels welded joints between T92 and HR3C

Grade 316L is a type of austenitic stainless steel with ultra-low carbon content and it exhibits superior corrosion resistance. However, pitting is always observed in 316L steel when it is exposed to media containing halide ions. In the present study, we found that in the presence of acetate acid (HAc) containing chloride or bromide ions, pitting occurred on the surface of the rotary steam pipes with the matrix material of 316L steel in terephthalic acid (TA) dryer. In order to identify the causes of the failure, metallographic structures and chemical compositions of the matrix material were inspected by an optical microscope (OM) and a photoelectric direct reading spectrometer. Beside these, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) as well as ion chromatography (IC) were used to analyze the micromorphologies of the corrosion pits and the chemical compositions of the corrosion deposits within them. Analysis of the results revealed the sources of halide ions and the factors accelerating the corrosion rate. Beside these, detailed mechanisms of pitting were discussed and six out of all the seven theoretical morphologies of pitting features were obtained in practice.

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Yi Gong

Papers

Microstructure and mechanical properties of dissimilar materials joints between T92 martensitic and S304H austenitic steels

Microstructural analysis on creep properties of dissimilar materials joints between T92 martensitic and HR3C austenitic steels

Assessment of creep rupture properties for dissimilar steels welded joints between T92 and HR3C

Pitting corrosion on 316L pipes in terephthalic acid (TA) dryer

Creep fracture behavior of dissimilar weld joints between T92 martensitic and HR3C austenitic steels