Magnetic Barkhausen emissions and microstructural degradation study in 1.25 Cr–0.50 Mo steel during high temperature exposure (original) (raw)
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Ndt & E International, 2007
Magnetic hysteresis loop and Barkhausen emissions were recorded and analysed for 5Cr-0.5Mo steel after ageing at 600 1C for various lengths of time. At the initial stage of ageing the interstitial carbon diffuses towards the grain boundary making the matrix magnetically softer. During this stage, extending up to 200 h of ageing, magnetic softness was found to be increasing. This was associated with a decrease in coercivity and increase in Barkhausen voltage. Beyond 200 h of ageing the precipitation of alloy carbides attain subsequent growth, making the material magnetically harder. The evolution of carbides was studied using SEM-EDAX analysis. It was observed that most of the carbides transformed into M 23 C 6 type after ageing for 400 h. r
Effect of hardness and composition gradients on Barkhausen emission in case hardened steel
Journal of Magnetism and Magnetic Materials, 2006
The effect of gradients in hardness, structure and composition in the surface layers on magnetic Barkhausen noise (MBN) was investigated in two widely used low alloy steels. One material was case hardened by induction hardening. The other was case carburised. Similar hardness profiles were produced by the two treatments. It was found that the variation in structure and hardness through the case in the induction-hardened steel had a minor effect on the MBN profile. In contrast, the inhomogeneity in the case-carburised material showed up clearly. This took the form of a broadened or two-peak MBN profile. When the surface layer containing the case was removed by etching, the broadened profile was replaced by a profile with a single peak. It is concluded that the shape and position of the MBN profile is significantly affected when a gradient in microstructure is induced by a gradient in carbon content. On the other hand, a gradient in microstructure induced by heat treatment with a constant carbon level has much less affect on the MBN profile for the induction-hardened steel.
Scripta Metallurgica Et Materialia, 1990
Morphological and compositional changes of carbides during service can produce deterioration in the creep strength. Their study and characterization are important since they can help residual life assessment[l-3]. The present paper describes the results of T~EDS investigation to study the morphological and compositional changes of carbides in a main steam pipe of ICr-0.3Mo-0.25V ferritic steels after ten years of service.
Microstructural Degradation in Power Plant Steels and Life Assessment of Power Plant Components
Procedia Engineering, 2013
Extensive creep testing was carried out on 1Cr1Mo¼ tempered) and aged condition. Both the steels exhibit the temperature range between 813 and 873 K (540°C higher temperature ranges. Casting steel showed wedge of forged steel, the voids were elliptical and flat which deformation and creep ductility of the two steels investi tertiary stage. Based on detailed microstructural investi damage mechanisms such as structural transformation, applied for remaining life assessment of the two steels. slightly on aging; both for rotor forging and casing Mo 2 C carbides and coagulation of others resulting in aging times was due to recovery in ferrite, gradual de and transitional character of precipitated carbides. Cre assessment calculations have also been carried out using
Magnetic characterization of HSLA steel by power-law decay exponents of Barkhausen emission signal
Journal of Magnetism and …, 2009
The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Microstructural evolution of 9Cr–1Mo steel during long term exposure at 550 °C
Thermal exposure changes in the microstructure of the 9Cr-1Mo steel, largely used in thermal power plants and petrochemical industry, have been investigated, through long term experience at 550 • C in furnace, up to 7000 hours. Detailed analysis of the microstructural evolution and changes in secondary carbides (M 23 C 6) were carried out through SEM, XRD and EDX analysis. Electrochemical extractions were done because of the small volume of carbides. A progressive restoration of the tempered martensite matrix was observed. Moreover, a continuous increase of M 23 C 6 size is revealed until stabilization after about 5000 hours of exposure. The nucleation of Laves phases is here found ; two inverse contributions may be concluded. When nucleating far from secondary precipitates, these phases grow by consuming matrix elements, which can trigger creep damages. Nevertheless, by surrounding the M 23 C 6 carbides like a shell, Laves phases can slow down their growth and so contribute in solid solution hardening. X-ray diffraction analysis lead to determine the temperature-time dependence of the matrix and M 23 C 6 lattice parameter.
Degradation Structures of the Steels Applied in Energetics
Manufacturing Technology, 2018
Currently, it is in the power industry exerted the pressure in terms of environmental impact and economics. That means requirements focussed on the development of high efficiency and low emission systems. Both of these requirements leads to the increasing of the thermal efficiency of a power plant and that means also increasing of the working temperatures. In the future, it will be necessary to develop materials that can withstand these demanding conditions and requirements. Strength of steel used at high temperatures is one of the properties which affect the life time of the power equipment. These properties strongly depend on microstructure of material. However, useful initial microstructures are unstable in service conditions. The changes come gradually at temperature-dependent rate through processes of thermal degradation. Many of these processes are caused by changes in the carbide structure of the steels and other phase transformations.This contribution deals with the degradation structures of the steels applied in energetics.
Nondestructive Characterization of Thermal Ageing Behaviour at 753 K in M250 Maraging Steel
Maraging steel M250 is widely used in aerospace industry for fabrication of critical rocket motor casings. Specific heat-treatment is given to these parts before they are put into service. Qualification of the heat treatments is presently based on the microscrostructural examination carried out on test coupons, which is indirect tedious, destructive in nature and only limited sampling based. For the complete, faster, accurate and insitu qualification of the actual heat treatment given to the actual component, non-destructive inspection techniques based methodology has been developed. Two NDE techniques, magnetic Barkhausen emission (MBE) and ultrasonic techniques have been used for the characterization of thermal ageing behaviour of the steel at 753 K. The MBE technique has been chosen due to the ferromagnetic nature of the maraging steel. While the MBE technique provides the near surface information, the ultrasonic technique characterizes the bulk of the component. The present study has clearly brought out the complementary nature of these two techniques for the characterization of thermal ageing behaviour in M250 maraging steel. Ultrasonic measurements have been found to be more sensitive to the precipitation of intermetallics, whereas, MBE could clearly identify the onset of austenitic reversion.
Nondestructive characterization of thermal ageing behavior at 753 K in M250 Maraging Steel
Maraging steel M250 is widely used in aerospace industry for fabrication of critical rocket motor casings. Specific heat-treatment is given to these parts before they are put into service. Qualification of the heat treatments is presently based on the microscrostructural examination carried out on test coupons, which is indirect tedious, destructive in nature and only limited sampling based. For the complete, faster, accurate and insitu qualification of the actual heat treatment given to the actual component, non-destructive inspection techniques based methodology has been developed. Two NDE techniques, magnetic Barkhausen emission (MBE) and ultrasonic techniques have been used for the characterization of thermal ageing behaviour of the steel at 753 K. The MBE technique has been chosen due to the ferromagnetic nature of the maraging steel. While the MBE technique provides the near surface information, the ultrasonic technique characterizes the bulk of the component. The present study has clearly brought out the complementary nature of these two techniques for the characterization of thermal ageing behaviour in M250 maraging steel. Ultrasonic measurements have been found to be more sensitive to the precipitation of intermetallics, whereas, MBE could clearly identify the onset of austenitic reversion.