Preet Singh

Austenitic carbon steels that exhibit excellent mechanical properties due to the twinning-induced plasticity effect have been studied extensively. On the other hand, austenitic stainless steels usually achieve good strength and ductility via transformation-induced plasticity. However, relying on martensite transformation for strength may cause problems such as delayed cracking. Therefore, the twinning behavior of a stable low-nickel high-manganese austenitic stainless steel (Type 201Cu) was studied. The steel showed extensive twin formation during deformation, which was observed using SEM-EBSD and HR-TEM. Consequently, a high strain hardening rate was seen, which can be attributed to the dynamic Hall-Petch effect. However, the yield strength was low as is typical for austenitic steels in the annealed condition. The yield strength was increased markedly by taking advantage of the twinned microstructure and the stability of the twins during annealing. Cold-rolling to a 33% reduction a...

Kraft recovery boilers experience localized accelerated corrosion in mid furnace areas. Corrosion patterns may vary from one boiler to other depending upon the operation parameters and general design of the boiler. Local gaseous environments were characterized in areas with corrosion and equivalent areas without accelerated corrosion in a selected boiler over the period of two years. Results from this study indicated that in the areas with accelerated corrosion there was a large variation in the local gas composition at the waterwall surface. Reducing and sulfidizing gases were found in the areas with accelerated corrosion whereas the gas compositions were more oxidizing in the low corrosion areas. Observations during field tests have indicated that the local waterwall temperature may also vary in the mid furnace due to localized combustion and air flow patterns. Mid-furnace environments were simulated in laboratory to evaluate the effect of gas composition and fluctuations on corro...

Condensate of black liquor vapors is known to cause corrosion in pulp mill equipment like digesters, flash tanks, storage tanks, evaporator domes, and other equipment handling black liquor condensate. This type of corrosion typically occurs in parts of equipment where the black liquor vapors can condense on a metal surface. Generally organic acids and other wood extractives in the condensate are thought to be responsible for the vapor phase corrosion of pulp mill equipment. Different wood species have different extractives at varying concentrations. Black liquor from softwood and hardwood were used in this study to characterize the corrosive constituents in different condensates. Seven alloys were tested in this study. Carbon steel corrodes at higher rates in the softwood condensate compared to the hardwood condensate. Austenitic stainless steel coupons experienced localized attack in both condensates. Chemical analysis of condensates have shown that although the hardwood condensate...

The Institute of Paper Science and Technology is an independent graduate school, research organization, • and information center for science and technology mainly concerned with manufacture and uses of pulp, paper, paperboard, and other forest products and byproducts. Established in 1929 as The Institute of Paper Chemistry, the Institute provides research and information services to the wood, fiber, and allied industries in a unique partnership between education and business. The Institute is supported by 40 member companies. The purpose of the Institute is fulfilled through four missions, which are: • to provide a multidisciplinary graduate education to students who advance the science and technology of the industry and who rise into leadership positions within the industry; • to conduct and foster research that creates knowledge to satisfy the technological needs of the industry; • to provide the information, expertise, and interactive learning that enable customers to improve job...

Wettability control of stainless steel surfaces has wide applicability due to the extensive use of stainless steels in industries that handle liquids. However, previous studies to achieve hydrophobicity on stainless steel surfaces rely on artificial roughness by added particles and residue formation that could compromise mechanical stability of the modified surface. In this study, water-repellent stainless steel surfaces were fabricated via the controlled topographical enhancement of intrinsic grain structures to achieve the required surface roughness. Electrochemical etching was used to control the relative etch rate between grains and grain boundaries by applying an anodic potential to stainless steel 316 (SS316). At low potential (1.2 V vs. Saturated Calomel Electrode), high selectivity between grain and grain boundary etching was observed, which resulted in significant etching at grain boundaries and smooth top grain surfaces. Morphologies with significant microscale roughness, and slight nanoscale roughness, were achieved with intermediate applied potentials (1.3–1.5 V). As the potential increased further (1.8 V), etch selectivity decreased and yielded microscopically smooth surfaces with sponge-like nanoscale roughness; at even higher potentials (2.4 V), electro-polishing was observed with surfaces that are smooth at the nanoscale. Based upon the relationship between anodic potential and topography, we designed a nano/microscale hierarchical SS316 surface by a two-step electrochemical etching combining low and high anodic potentials. The hierarchical SS316 surface resulted in a water contact angle of 137.5 ± 5.0°. Plasma-assisted deposition of a fluorocarbon film further reduced the wettability, with a contact angle of 163.9 ± 1.2° and a roll-off angle of 10.7 ± 1.8° for 4 μL water droplets, thereby rendering the modified SS316 surfaces superhydrophobic. Due to the inherently robust intrinsic grain structure of SS, we expect that this simple approach to generate water-repellent SS316 surfaces will display improved mechanical robustness relative to previous approaches.

The purpose of the overall research project is to determine methods which may be applied economically to mitigate corrosion of reinforcement in precast prestressed concrete piles in Georgia’s marine environments. The overall goal is to improve the durability of bridge piles so that a design life of 100 years may be achieved. The research has four specific objectives. The first objective is to determine the extent of corrosion damage in Georgia’s structural concrete bridge piling and the success of methods used to improve the durability of bridge piles in Georgia. The second objective is to fully document past research and investigations on the durability of structural concrete in the marine environment with particular emphasis on the corrosion of reinforcement and its mitigation. The latter includes learning from state departments of transportation: finding from their experiences with corrosion mitigation including the effect of concrete quality and cover and with regard to types of...

Duplex stainless steels (DSS) have generally performed very well in the pulp mill environment. However, some corrosion and stress corrosion cracking (SCC) of duplex stainless steels has been reported in different pulping liquors. Studies have shown that corrosion ...

... Stefanie L. Asher School of Materials Science and Engineering Georgia Institute of Technology Atlanta, GA 30332 Preet M. Singh School of Materials Science and Engineering Georgia Institute of Technology Atlanta, GA 30332 Jeffery A. Colwell Battelle 505 King Ave Columbus ...

Pressurized water reactor of integral configuration (iPWR) offers inherent safety features, such as the possibility to completely eliminate large-break LOCA and control rod ejection. However, integral configuration implemented using the current PWR technology leads to a larger reactor vessel, which in turn, due to the vessel manufacturability and transportability restrictions, limits the reactor power. It is reflected in the fact that there are many proposed iPWR SMR concepts, with power levels up to approximately 300 MWe, but not many iPWR concepts with power level corresponding to that of large traditional PWR NPPs (900 MWe or higher). While SMRs offer certain advantages, they also have specific challenges. Moreover, large energy markets tend to prefer NPPs with larger power. The Integral Inherently Safe Light Water Reactor (I2S-LWR) concept is an integral PWR, of larger power level (1000 MWe), that at the same time features integral configurations, and inherent safety features ty...

High Velocity Oxy-Fuel (HVOF) thermal spraying is extensively used in industry to produce high-density, low porosity functional coatings to resist severe wear and corrosion. Increasingly there is a need to provide high-quality coatings that resist both wear and corrosion at high temperatures at the same time. Very few engineering data exist on such coatings. In this paper, a study of HVOF coatings of Co-Cr-Mo alloys, that relies on Laves phases or on carbides for wear and corrosion resistance is reported. The paper covers the basic metallurgy of the alloys, their design and microstructure. The oxidation and sulfidation resistances of the coatings are evaluated at 600 C. The high-temperature hardness and the room-temperature abrasion resistance, hardness and bond strengths are compared to assess their utility in high-temperature corrosion and wear-resistant applications. The test results indicate that these alloys are strong candidate materials for providing protection in the form of...

This article reviews the tensile properties and toughness characteristics of discontinuously reinforced aluminum (DRA) composites in terms of particle spacing, particle size, volume fraction, matrix alloy, and matrix microstructure. Both fracture toughness data and impact toughness data of the DRA composites are summarized. The article discusses the effects of confining pressure on the ductility of the DRA materials. It describes the fatigue behavior, such as stress-life behavior, strain-life behavior, and fatigue crack propagation, of the DRA.

Degradation of metallic materials in biofuel environments has recently become an emergent problem due to the increasing demand of the renewable biomass-based energy source. In simulated fuel-grade ethanol environment (SFGE), stress corrosion cracking 1-3 and pitting corrosion 4 were reported as major corrosion failures on carbon steel. The anodic activity of carbon steel in ethanolic environment is very different from that in the aqueous environment. It has been widely concluded that the anodic behavior of carbon steel, such as surface film growth kinetics and dissolution, can be largely changed due to a slight change in ethanol chemistry. Compared to the study in the anodic behavior, there is much less work which has been done towards understanding the cathodic activity on the steel surface in ethanolic environment. In methanolic environment, Brossia et. al reported a unique proton hopping mechanism to explain the cathodically controlled corrosion process 5 . But no similar systematic work has been reported in ethanolic environments. In a corrosion system, the kinetics of cathodic reaction can form as a limiting step to determine the corrosion rate. Hydrogen activity can also lead to hydrogen embrittlement in a certain environment. In this contribution, we report our investigation on the cathodic activity of carbon steel in SFGE. The reaction type and kinetics were studied in details. Environmental parameters and stress conditions of the hydrogen embrittlement on carbon steel in SFGE were discussed and analyzed. Due to the high resistivity in SFGE, a specially-designed electrochemical cell was used to enable the reliable electrochemical measurement for this study. Potentiodynamic polarization and potentiostatic polarization were employed to understand the cathodic activities in SFGE using both carbon steel and platinum electrodes. The kinetics of reaction steps were further discussed using electrochemical impedance spectroscopy (EIS) and its equivalent circuit modeling. Hydrogen permeation test and slow strain rate test (SSRT) were carried out under open-circuit potential (OCP) and various conditions to study the possible hydrogen embrittlement of carbon steel in SFGE. As shown in Figure 1, the cathodic behaviors of the platinum electrode in SFGE are shown under aeration and de-aeration conditions. Under aeration, cathodic reaction follows oxygen reduction line at relatively higher potentials. These results show that the O2 is the major cathodic reactant to support the corrosion reaction in aerated SFGE. When the SFGE solution was de-aerated using N2, as shown in Figure 1, much lower cathodic potentials and clear limiting currents are present. Without O2, hydrogen evolution from free proton in the solution, as well as the further reduction of alcohols and other organic solvents at higher overpotential, may participate in the cathodic reaction. The products from these

Abstract Nonlinear ultrasound (NLU) has been shown to be sensitive to microstructural features including precipitates and dislocations. The heat-affected zone (HAZ) of welded austenitic stainless steels can be susceptible to intergranular stress corrosion cracking (IGSCC). This research uses NLU to evaluate the microstructure of the HAZ with an emphasis on dislocations, precipitates, grain size/morphology and sensitization, which is the formation of chromium carbide precipitates at the grain boundaries. The results show that there is a large increase in the measured acoustic nonlinearity parameter in the vicinity of the HAZ, which can be used to monitor changes in microstructure such as sensitization.

"March 8, 2000." Project F018. Recovery boiler corrosion / Preet M. Singh ... [et al.] ; Project F019. Corrosion in closed cycle mills / Preet M. Singh Greg Fonder, Jamshad Mahmood ; Project F036. Mechanisms and prevention of stress-assisted waterside corrosion in recovery boilers / Preet Singh, Greg Fonder, Jamshad Mahmood ; Project F037. Corrosivity of black liquors / Preet Singh, Greg Fonder, Jamshad Mahmood -- Slide Material.

ABSTRACT The steam oxidation of austenitic steel 10Cr18Ni9Cu3NbN at about 605 °C after in service for 12,000 h and 34,696 h in a 660 MW USC power plant was investigated. Results show that a double layer structure consisting of a magnetite outer layer and Cr-rich inner layer was observed. After 12,000 h, shot blasting treatment improved the steam oxidation resistance of 10Cr18Ni9Cu3NbN steel compared with previous report. Scale oxide which was beneficial from shot blasting treatment spalled off within a short time before 34,696 h. After initial scale exfoliation, the newly formed scale oxide was more likely to be the oxide in 9–12%Cr steels, which was attributed to the low chromium under the initial oxide.

AC impedance spectroscopy was used to investigate copper plated-through-holes (PTH) in glass fiber reinforced epoxy substrates (FR4) at different stages of temperature-humidity-bias driven electrochemical migration failure. The test vehicles consisted of PTHs arranged in an alternate anode and cathode configuration in FR4 boards. The test vehicles were subjected to accelerated stress testing [130 °C, 85 % relative humidity (RH) and 100 V DC] to initiate a specific sub-surface electrochemical failure mode referred to as conductive anodic filament (CAF) formation. The test vehicle variations included a control with no exposure, test vehicle with electrical insulation failure (resistance change to 1 MΩ during the test) and test vehicle with initiation of CAF to compare the impedance characteristics at different stages of electrochemical migration failure. AC impedance measurements were carried out on the test vehicle variations at ambient and in an in situ humidity chamber as a function of RH at 14–85 %. The prior exposure condition of the test vehicles was found to have a strong effect on the impedance characteristics at different RH values. The accelerated testing results and impedance characteristics of the PTHs in epoxy-glass fiber substrates are discussed.

ABSTRACT The stress corrosion cracking (SCC) susceptibility of carbon steel in fuel grade ethanol varies as a function of major and minor constituents in ethanol. The results of a round-robin testing on six different ethanol batches are presented. Significant variations in test results between the laboratories may result from apparently minor differences in test procedures. The variation in SCC susceptibility of different ethanol chemistries appear to be small.