• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2591-2599
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• 2021

The effect of thermal aging at 475 ℃ and 750 ℃ of Z3CN20.09M cast duplex stainless steel (CDSS) on microstructure, mechanical and intergranular corrosion properties were investigated by transmission electron microscope (TEM), nano indenter, scanning electron microscope (SEM) and corrosion fatigue test system. The result indicated that the spinodal decomposition and G precipitated were occurred after aged at 475 ℃, as well as sigma precipitated at 750 ℃. The microstructure degeneration of ferrite was saturated after aged for 2000h and 200 h at 475 ℃ and 750 ℃ respectively. The mechanical properties, intergranular corrosion resistance and corrosion fatigue lives were continuing deteriorated with increasing the aging time at both temperatures. The difference of the degeneration mechanisms of Z3CN20.09M CDSS aged at 475 ℃ and 750 ℃ was analyzed.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.141-148
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• 1995

Fatigue tests were carried out by a rotary bending testing machine of cantilever type. M.E.F.(ferrite encapsulated islands of martensite) materials were made by a series of heat treatment from a low carbon steel(SM 20 C). The fatigue tests were conducted at stress levels of 302 MPa and with frequencies of 25Hz, 2.5 Hz and 0.5 Hz in 3% NaCl solution. The fatigue strength increased with frequency got higher. The microcracks and corrosion pits were generated at the boundary between the matrix and the 2nd phase. The cracks generated by the corrosion pits were coalesced with the pits around the notch and became the initial crack. The $N_i/N_f$ ratio increased as the frequency and stress level decreased. The interference phenomenon increased with stress level and frequency gots higher. The crack propagation rate was delayed as the stress level lowers and the frequency gets higher, however, the range of the stress intensity factor depended only on a stress level.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1381-1389
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• 2012

The object of this study considers corrosion fatigue improvement of 7075-T6 aluminum by using shot peening treatment on 3.5% NaCl solution at room temperature. Aluminum alloy is generally used in aerospace structural components because of the light weight and high strength characteristics. Many studies have shown that an aluminum alloy can be approximately 50% lighter than other materials. Mostly, corrosion leads to earlier fatigue crack propagation under tensile conditions and severely reduces the life of structures. Therefore, the technique to improve material resistance to corrosion fatigue is required. Shot peening technology is widely used to improve fatigue life and other mechanical properties by induced compressive residual stress. Even the roughness of treated surface causes pitting corrosion, the compressive residual stress, which is induced under the surface layer of material by shot peening, suppresses the corrosion and increases the corrosion resistance. The experimental results for shot peened specimens were compared with previous work for non treated aluminum alloy. The results show that the shot peening treatment affects the corrosion fatigue improvement of aluminum alloys and the induced compressive residual stress by shot peening treatment improves the resistance to corrosion fatigue.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.363-368
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• 2024

Steel structures used in marine environments, such as ships, offshore structures or sub-structures in wind power generation facilities are prone to corrosion. In this study, the corrosion fatigue crack propagation characteristics due to the environmental load are examined by experiment at -1050 mV vs. SCE, which is equivalent to the anti-corrosion potential of zinc anodes that are widely used as sacrificial anodes. In this study, for this purpose, an experimental study is conducted on the effect of cathodic protection on the propagation of fatigue cracks in the seawater environment under the condition of -1050 mV vs. SCE, considering the wave period in synthetic seawater. Cathodic protection prevents corrosion; however, excessive protection generates hydrogen through chemical reactions as well as calcareous deposits. The fatigue crack propagation rate appeared to be faster than the rate in a seawater corrosion environment at the early stages of the experiment. As the crack length and stress intensity factor K increased, the crack propagation rate became slower than the fatigue crack propagation rate in seawater. However, the crack growth rate was faster than that in the atmosphere.

• Journal of Ocean Engineering and Technology
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• v.17 no.3 s.52
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• pp.39-45
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• 2003

Shot peening is an effective method of improving the fatigue strength of components and structures. The compressive residual stress produced by surface plastic deformation with shot peening is usually regarded as the major factor in increasing fatigue strength. In this study, the influence of shot peening on corrosion was investigated. Spring steel immersed in $3.5\%$ NaCl prior was used to evaluate the effect of shot peening on fatigue properties. The immersion test was performed on the five kinds of specimens with shot peened and unpeened. The distributions of residual stresses of shot peened spring steels were measured in an X-ray diffraction apparatus, using the two-point method. Corrosion potential, polarization curve, residual stress, etc. were investigated, based on the experimental results. From test results, the effect of shot peening on the corrosion was evaluated.

• Corrosion Science and Technology
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• v.10 no.3
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• pp.77-79
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• 2011

The research trend in the corrosion behaviour of stainless steel weldment has been reviewed. The welding technology plays an important role in the fabrication of structure such as chemical plant, power plant, because welding can influence various factors in the performance of plant and equipment. This has led to an increasing attention towards the corrosion behaviour of weldment which has been one of the major issues for both welding and corrosion research engineers. The aim of this paper is to give a short survey of the recent technical trends of welding and corrosion including the electrochemical corrosion, stress corrosion cracking, and corrosion fatigue in connection with the welding materials, welding process, and welding fabrication. This study covers the corrosion behaviour of stainless steel weldment collected from the COMPENDEX DB analysis of published papers, research subject and research institutes.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.173-178
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• 2008

Recently an electrochemical noise method (ENM) with three electrodes has gained attention as a corrosion monitoring system in chemical plants. So far a few studies have been carried out for localized corrosion and environmental cracking of chemical plant materials. In this paper the ENM system is briefly summarized. Then an application of ENM to general corrosion for chemical plant materials is described. The emphasis is focused upon the analysis of stress on the corrosion cracking process of austenitic stainless steel in 30% $MgCl_2$ aqueous solution and the corrosion fatigue crack initiation process of 12 Cr stainless steel in 3% NaCl aqueous solution by ENM. Finally future problems for ENM to monitor regarding corrosion and environmental cracking in chemical plants are discussed.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.139.1-146
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• 2001

Contact lines are necessary to supply electric locomotives with electric power. As most railways are gradually electrified with modernized electric cars, the demand for catenary wires and their facilities are also increased. Catenary wires made by metallic materials are generally used in the open air. They are exposed to the marine area with air-borne salt or severely polluted industrial area with much corrosive emission gases depending on the railway locations. In urban area, acid rain may cause a degradation of catenary wire system. Corrosion of catenary wires can make their actual lifetime shorter than that originally designed. Thus, the messenger wires, a kind of catenary wire system, were investigated with respect to corrosion, which include new and the used one collected at the field. They are also vibrated with some amplitude everytime the train passes through the railway. The frequent cyclic load on the wire any result in a fatigue damage, Surface damage by corrosion can make fatigue crack initiate with ease. In the present study, the fatigue life of the used wire was measured 40 to 50% shorter than that of new one in average.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.102-107
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• 2004

Suspension part should have enough endurance during its lifetime to protect passenger. Therefore, the coil spring is one of the major suspension part of an automobile. Corrosion fatigue strength of the coil spring depends on many factors including mechanical and environmental properties. In this paper, residual stresses by shot peening was analyzed using finite element analysis and evaluated its effect on corrosion fatigue strength.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.558-567
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• 2003

The catenary wires are damaged by periodic running of train as well as repeated stress. The wires are also degraded by atmosphere corrosion at fields. Corrosion of wires increased surface roughness and deteriorated mechanical properties by providing fatigue crack initiation sited resulting in a bad effect on service life of the wires. Fatigue test of catenary wires performed to estimate service lifetime. Also, simulation to analyze stress on catenary wires was conducted through modelling the finite elements for dynamic behaviors of wires. Fatigue life of catenary wires was estimated with fatigue and simulation tests.