Microstructure characterization and HCF fracture mode transition for modified 9Cr-1Mo dissimilarly welded joint at different elevated temperatures

Shao, Chendong; Lu, Fenggui; Xiongfei, Wang; Ding, Yuming; Li, Zhuguo

doi:10.1016/j.jmst.2016.12.001

Cited by 14 publications

(3 citation statements)

References 31 publications

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“…Other fatigue traits can also be clearly observed from the fracture surface, i.e., secondary cracks, under In the high cycle fatigue (HCF) regime, surface-induced cracking or large inclusion cracking is commonly observed [32,33]. For example, crack initiation sites were found at the surface, at detectable shrinkage porosities and at internal large inclusions (in 100 µm scale) in modified 9Cr-1Mo ferritic steel [34]. In the current study, because of the L-PBF process with optimized printing parameters and post treatment including HIP, large inclusions are not expected.…”

Section: Fatigue Fracturementioning

confidence: 99%

Cyclic Deformation Behavior of Additive-Manufactured IN738LC Superalloys from Virgin and Reused Powders

Chen

Segersäll

et al. 2022

Materials

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In laser powder bed fusion (L-PBF), most powders are not melted in the chamber and collected after the printing process. Powder reuse is appreciable without sacrificing the mechanical properties of target components. To understand the influences of powder reuse on mechanical performance, a nickel-based superalloy, IN738LC, was investigated. Powder morphology, microstructure and chemical compositions of virgin and reused powders were characterized. An increase in oxygen content, generally metallic oxides, was located on the surface of powders. Monotonic tensile and cyclic fatigue were tested. Negligible deterioration in strength and tensile ductility were found, while scattered fatigue performance with regard to fatigue life was shown. Deformation and fatigue crack propagation mechanisms were discussed for describing the powder degradation effects.

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Section: Fatigue Fracturementioning

confidence: 99%

Cyclic Deformation Behavior of Additive-Manufactured IN738LC Superalloys from Virgin and Reused Powders

Chen

Segersäll

et al. 2022

Materials

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“…They suggested that soft zone and micro-defects would be considered in fatigue design and welding material selection. Shao et al [23] discovered that HCF fracture mode for 9Cr-1Mo dissimilarly welded joint at different temperatures. However, there have been few reports on the welding and fatigue performance of 30Cr1Mo1V and 30Cr2Ni4MoV steels.…”

Section: Introductionmentioning

confidence: 99%

High cycle fatigue behavior of a dissimilar metal welded joint in ultra-supercritical steam turbine rotor

Wang

Zhu

et al. 2020

Mater. Res. Express

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The high cycle fatigue (HCF) property and microstructure of a dissimilar metal welded joint (DMWJ) for ultra-supercritical steam turbine rotor were systematically investigated in this paper. The DMWJ was fabricated using narrow gap submerged arc welding (NG-SAW) technique with buttering layer. Conditional fatigue strength of 30Cr1Mo1V (BM-1), buttering layer (BL), weld metal (WM) and 30Cr2Ni4MoV (BM-2) based on S-N curve was obtained by HCF tests at room temperature. The microstructure and second-phase carbide as well as fracture appearance of BM-1, BL, WM and BM-2 were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results show that the BL has lower fatigue strength, which are related to more content of the soft ferrite and less content of the hard carbide. The acicular ferrite represents better fatigue properties than massive ferrite due to barrier effect. Additionally, dislocation density sharply increases near the carbides, grain boundaries, and lath structures resulting in dislocation tangle after HCF test, which helps to improve the fatigue strength of the welded joint. The carbide precipitated, aggregated, and grown in the grain boundaries promoted crack nucleation, reduced the crack propagation rate and affected the crack propagation path.

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“…Table 1 shows the developing martensitic heat resistant steels over the years [34,35]. Recently, B containing 9% Cr martensitic heat resistant steel (9Cr-B steel) with excellent creep property was developed, i.e., B containing 9Cr-3W-3Co series steels developed by National Institute for Materials Science (NIMS) in Japan [36][37][38][39][40][41][42][43][44][45][46][47][48][49] and FB2 steel in the frame of the European Cooperation in Science and Technology (COST) program [50][51][52][53][54][55][56][57][58][59][60]. More specially, compared with conventional martensitic steel, the difference of creep strength between base metal and weld joint of 9Cr-B steel was negligible [61], as shown in Figure 2 [62].…”

Section: Introductionmentioning

confidence: 99%

A Review of Austenite Memory Effect in HAZ of B Containing 9% Cr Martensitic Heat Resistant Steel

Cai

et al. 2019

Metals

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During the welding process of B containing 9% Cr martensitic heat resistant steel (9Cr-B steel), austenite memory effect (referred to that the prior austenite grains in the heat affected zone (HAZ) after welding inherit the shape and size of prior austenite grains before welding) occurs in its normalized sub-zone of HAZ and the grain refinement is suppressed, which can effectively prevent type IV crack, and improve the service life of the welded joint at high temperatures. In the present article, α/γ reverse transformation behavior in the normalized sub-zone of 9Cr-B steel HAZ is reviewed. Austenite memory effect of 9Cr-B steel is derived from B addition. The main mechanisms of austenite memory effect during α/γ reverse transformation are discussed. Various models of boron causing austenite memory effect are discussed in detail. Matrix microstructure also plays an important role in austenite memory effect. Effects of heating rate, peak temperature, and holding time at peak temperature on austenite memory effect are also discussed.

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Microstructure characterization and HCF fracture mode transition for modified 9Cr-1Mo dissimilarly welded joint at different elevated temperatures

Cited by 14 publications

References 31 publications

Cyclic Deformation Behavior of Additive-Manufactured IN738LC Superalloys from Virgin and Reused Powders

Cyclic Deformation Behavior of Additive-Manufactured IN738LC Superalloys from Virgin and Reused Powders

High cycle fatigue behavior of a dissimilar metal welded joint in ultra-supercritical steam turbine rotor

A Review of Austenite Memory Effect in HAZ of B Containing 9% Cr Martensitic Heat Resistant Steel

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