Hot conditioning operation of the primary heat transport system is an important step prior to the... more Hot conditioning operation of the primary heat transport system is an important step prior to the commissioning of Pressurized Heavy Water Reactors. One of the major objectives of the operation is to develop a stable and protective magnetite layer on the inner surfaces of carbon steel ...
The various stages that the stainless steel tube undergoes in the course of fabrication decide th... more The various stages that the stainless steel tube undergoes in the course of fabrication decide the nature and level of residual stress induced in the final tubing. The effect of residual stress on the stress corrosion cracking susceptibility of 304 stainless steel was studied by ...
This study aims to understand the mechanism of increased SCC susceptibility of machined 304L stai... more This study aims to understand the mechanism of increased SCC susceptibility of machined 304L stainless steel in chloride environment. Austenitic stainless steel grade 304L was surface machined up to a depth of 0.5 mm from the surface. In depth characterization was carried out by optical, scanning electron microscopic technique, hardness measurement and by EBSD and XRD studies. The stress corrosion cracking (SCC) susceptibility was estimated by exposing constant strained samples made up of machined and unmachined stainless steel to 5 M H2SO4 + 0.5 M NaCl solution at room temperature (28 °C) until cracking. In addition strips of machined and unmachined stainless steel were exposed to boiling MgCl2 solution as per ASTM G36 to understand the effect of residual stress and strain generated due to machining on the SCC susceptibility. The study reveals that surface machining results in extensive grain refinement, strain induced martensite transformation and high magnitude of plastic deformation near the surface.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010
ABSTRACT Effect of plastic deformation induced by cold rolling or surface machining on the suscep... more ABSTRACT Effect of plastic deformation induced by cold rolling or surface machining on the susceptibility to chloride-induced stress corrosion cracking at ambient temperature of 304L austenitic stainless steel was investigated in this study. The test material was subjected to three treatments: (a) solution annealed, (b) cold rolled and (c) surface machined to induce different levels of strain/stresses in the material. Subsequently constant strained samples were produced as per ASTM G30 for each condition and these were exposed to 1M HCl at ambient temperature until cracking occurred. Subsequently the cracked samples were characterized using stereo microscopy, optical microscopy and atomic force microscopy to understand the effect of microstructural changes produced by straining on the susceptibility to stress corrosion cracking at ambient temperature. Strained surface produced by machining accelerated the process of crack initiation resulting in densely distributed shallow surface cracks in a very short period of time as compared to solution annealed and cold worked sample. Crack propagation in cold worked sample was along the slip lines and cracking occurred much earlier than in the solution annealed sample.
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2009
The aim of this report is to examine the influence of sensitization on the mechanical properties ... more The aim of this report is to examine the influence of sensitization on the mechanical properties of AISI grade 304LN stainless steel with special emphasis on its fracture toughness. A series of stainless steel samples has been sensitized by holding at 1023 K for different time periods ranging from 1 to 100 hours followed by water quenching. The degree of sensitization (DOS) for each type of the varyingly heat-treated samples has been measured by an electrochemical potentiodynamic reactivation (EPR) test. The microstructures of these samples have been characterized by optical metallography, scanning electron microscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses, together with measurements of their hardness and tensile properties. The fracture toughness of the samples has been measured by the ball indentation (BI) technique and the results are validated by conducting conventional J-integral tests. It is revealed for the first time that the fracture toughness and ductility of AISI 304LN stainless steel deteriorate significantly with increased DOS, while the tensile strength (TS) values remain almost unaltered. The results have been critically discussed in terms of the depletion of solid solution strengtheners, the nature of the grain boundary precipitations, and the strain-induced martensite formation with the increasing DOS of the 304LN stainless steel.
Hot conditioning operation of the primary heat transport system is an important step prior to the... more Hot conditioning operation of the primary heat transport system is an important step prior to the commissioning of Pressurized Heavy Water Reactors. One of the major objectives of the operation is to develop a stable and protective magnetite layer on the inner surfaces of carbon steel ...
The various stages that the stainless steel tube undergoes in the course of fabrication decide th... more The various stages that the stainless steel tube undergoes in the course of fabrication decide the nature and level of residual stress induced in the final tubing. The effect of residual stress on the stress corrosion cracking susceptibility of 304 stainless steel was studied by ...
This study aims to understand the mechanism of increased SCC susceptibility of machined 304L stai... more This study aims to understand the mechanism of increased SCC susceptibility of machined 304L stainless steel in chloride environment. Austenitic stainless steel grade 304L was surface machined up to a depth of 0.5 mm from the surface. In depth characterization was carried out by optical, scanning electron microscopic technique, hardness measurement and by EBSD and XRD studies. The stress corrosion cracking (SCC) susceptibility was estimated by exposing constant strained samples made up of machined and unmachined stainless steel to 5 M H2SO4 + 0.5 M NaCl solution at room temperature (28 °C) until cracking. In addition strips of machined and unmachined stainless steel were exposed to boiling MgCl2 solution as per ASTM G36 to understand the effect of residual stress and strain generated due to machining on the SCC susceptibility. The study reveals that surface machining results in extensive grain refinement, strain induced martensite transformation and high magnitude of plastic deformation near the surface.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010
ABSTRACT Effect of plastic deformation induced by cold rolling or surface machining on the suscep... more ABSTRACT Effect of plastic deformation induced by cold rolling or surface machining on the susceptibility to chloride-induced stress corrosion cracking at ambient temperature of 304L austenitic stainless steel was investigated in this study. The test material was subjected to three treatments: (a) solution annealed, (b) cold rolled and (c) surface machined to induce different levels of strain/stresses in the material. Subsequently constant strained samples were produced as per ASTM G30 for each condition and these were exposed to 1M HCl at ambient temperature until cracking occurred. Subsequently the cracked samples were characterized using stereo microscopy, optical microscopy and atomic force microscopy to understand the effect of microstructural changes produced by straining on the susceptibility to stress corrosion cracking at ambient temperature. Strained surface produced by machining accelerated the process of crack initiation resulting in densely distributed shallow surface cracks in a very short period of time as compared to solution annealed and cold worked sample. Crack propagation in cold worked sample was along the slip lines and cracking occurred much earlier than in the solution annealed sample.
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2009
The aim of this report is to examine the influence of sensitization on the mechanical properties ... more The aim of this report is to examine the influence of sensitization on the mechanical properties of AISI grade 304LN stainless steel with special emphasis on its fracture toughness. A series of stainless steel samples has been sensitized by holding at 1023 K for different time periods ranging from 1 to 100 hours followed by water quenching. The degree of sensitization (DOS) for each type of the varyingly heat-treated samples has been measured by an electrochemical potentiodynamic reactivation (EPR) test. The microstructures of these samples have been characterized by optical metallography, scanning electron microscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses, together with measurements of their hardness and tensile properties. The fracture toughness of the samples has been measured by the ball indentation (BI) technique and the results are validated by conducting conventional J-integral tests. It is revealed for the first time that the fracture toughness and ductility of AISI 304LN stainless steel deteriorate significantly with increased DOS, while the tensile strength (TS) values remain almost unaltered. The results have been critically discussed in terms of the depletion of solid solution strengtheners, the nature of the grain boundary precipitations, and the strain-induced martensite formation with the increasing DOS of the 304LN stainless steel.
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