Protective Scale Research Articles

The effect of Al and Ti on the microstructure, mechanical properties and oxidation resistance of γ′-Ni3(Al, Ti) strengthened austenitic stainless steels

Both Al and Ti are the key elements for the formation of γ′-Ni3(Al, Ti) phase and protective oxide scale in the γ′-Ni3(Al, Ti) precipitation strengthened austenitic stainless (AS) steels. To obtain good mechanical properties, especially at elevated temperatures, high volume fraction of γ′ phase is required, which is strongly dependent on the total amounts of Al and Ti. For a given concentration of (Al + Ti), changing Al or Ti addition also has significant effects on the microstructure, mechanical properties and oxidation resistance of alloys. In this study, three alloys are designed by moderately adjusting Al and Ti addition while keeping (Al + Ti) concentration constant (8.7 at.%). It is found that increasing Ti and decreasing Al addition lead to fine Laves precipitates and close spacing between them, which in turn refine grain size and enhance strength at temperature lower than 750 °C. But at about 800 °C, the strength of there alloys is almost the same. Increasing Al and decreasing Ti addition have no apparent influence on the γ′ phase but promote the formation of B2–NiAl phase, resulting in reduced ductility at elevated temperature. Besides, high Al addition facilitates the formation of continuous protective oxide layer (mainly alumina) and is beneficial for oxidation resistance at 750 °C for 500 h. As Ti replaces Al, the integrity of protective alumina layer is destroyed and the discontinuous Al-rich oxides are interlaced with Cr-rich and Ti-rich oxides.

The microstructure and high-temperature oxidation resistance of Si-rich Mo-Si-B coatings prepared by ultrasonic vibration assisted laser cladding

Si-rich Mo-Si-B powders (Mo-62Si-5B at%) were deposited on Nb-Si based alloy by laser cladding assisted with ultrasonic vibration. The obtained coatings mainly consist of MoSi2 and (Mo, X)5Si3 (X = Nb and Ti). With the introduction of ultrasonic vibration during laser cladding, the lath-shaped MoSi2 phase transforms into cellular gradually. Meanwhile, the discrepancy on the microstructure of the top region and the bottom region is eliminated gradually, indicating that the cavitation and acoustic streaming of ultrasonic vibration not only refines the microstructure, but also homogenizes the element and phase distribution in the coatings. High-temperature oxidation experiment at 1250 ℃ were conducted to assess the oxidation resistance of the coatings. Compared with Nb-Si alloy, the coated specimens have much lower oxidation weight increase. Furthermore, with the assistance of ultrasonic vibration, the oxidation resistance of the coating is enhanced further. The oxide scales on the coatings consist of two layers: an upper amorphous aluminoborosilica with TiO2 particles dispersed and a lower crystalline SiO2 layer. With the introduction of ultrasonic vibration, the microstructure of the coatings is refined, resulting in more phase and grain boundaries in the coatings. Therefore, the diffusion of the elements to the surface is accelerated and the protective oxide scale can be formed quickly.

Challenges in computationally designing high temperature Fe-based austenitic alloys: Addressing the role of Ni additions

Alumina-forming austenitic (AFA) alloys are relatively inexpensive high performance materials which combine the creep resistance of low-cost austenitic alloys and the oxidation resistance of expensive alumina forming alloys. However, a fundamental understanding of the role of key alloying elements such as Ni, Cr, Al, Nb, Ti, V, B and C in the experimentally observed oxidation behavior of these alloys is still lacking. The present work is a first in a series of studies aiming to quantitatively describe the role of Ni in promoting or disrupting protective Al2O3 scale formation on AFA alloys. Ternary Fe-Al-xNi model alloys with three different Ni contents were isothermally exposed in an atmosphere with a low partial pressure of oxygen between 800–1000 °C for 24 h to evaluate the role of Ni in the observed internal oxidation behavior. Increasing Ni contents had no impact on the internal oxidation behavior of the alloys. The experimental and theoretical analyses in the present work suggested a negligible effect of the internal oxide precipitates on the inward diffusion of oxygen, typically expected in these systems, while simultaneously highlighting the barriers in the development of reliable models for computation-assisted design of these alloys.

Applying the Protective Gambling Beliefs Scale (PGBS) among Chinese gamblers and testing its association with responsible gambling

ABSTRACT Accurate and rational gambling beliefs have been found to play a protective role against gambling disorder (GD) and add unique insights into the prevention and intervention of gambling-related harms. Adopting the Protective Gambling Beliefs Scale (PGBS) as a measurement tool of these gambling beliefs, this study tested its psychometric properties and whether these gambling beliefs were associated with responsible gambling (RG) behaviors with a probability community sample of adult gamblers (N = 464) in Macao, China. Consistent with the past studies, PGBS was found unidimensional with high reliability. The construct validity of PGBS was verified by its negative associations with gambling-related interpretive biases and GD symptoms. Moreover, we found a significant and positive association between protective gambling beliefs and RG behaviors after controlling for the effects of gambling-related interpretive biases and demographic variables. Conventional approaches to gambling harm reduction focus more on maladaptive cognition. Our findings may offer empirical evidence that protective gambling beliefs also help reduce gambling-related harms and enable gamblers to keep their gambling at a relatively safe level. PGBS is not only a valid and reliable instrument to measure gamblers’ protective gambling beliefs but also a potential means to promote RG practices.

How to balance protection and development? A comprehensive analysis framework for territorial space utilization scale, function and pattern

The harmonious coexistence of man and nature is a universally recognized standard to test the rational utilization of multifunctional territorial space, and the planning of territorial space adapted to nature is a scientific guide to balance ecological protection and human development. This study focuses on the inevitable relationship between the scale, function and pattern of territorial space utilization (TSU), and puts forward a process research framework of “background evaluation-advantage comparison-optimization conduction”. Based on the evaluation of resource and environment suitability, this paper determines the scale of multifunctional territorial space through the potential conflict identification model of TSU. The location entropy method is used to identify the advantageous functions of the county level, and the matching characteristics of the research results and the current situation are obtained by comparing them with the current plan. Finally, from the county functional zoning to the regional TSU pattern, the corresponding optimization conduction path is designed to form a new development and protection pattern. The empirical results of research area show that: (1) The study area is suitable for urban construction and agricultural production as a whole. The ecological protection is mainly at the general important level, and there is a moderate potential conflict between the development and protection of territorial space. The space scale of urban construction, agricultural production and ecological protection are accounted for 8.77%, 78.71% and 12.52%, respectively. (2) The advantageous function of TSU in county-level administrative units is dominated by single advantageous function, and the number of composite advantageous functions is generally small. The advantageous functional types determined by this research have a high matching with the current plan. (3) Based on the analysis of the scale structure and functional use of territorial space, this paper defines the ecological space that should be strictly protected and the agricultural and urban space that should be moderately developed for production and construction, and sets up elastic development areas. Finally, a strategic pattern of “one corridor, two screens, three circles and four zones” is conducive to the realization of the beautiful vision of the unification of protection and development.

Effect of oxygen doping on the corrosion behavior of nanocrystalline coating under the synergy of solid NaCl deposit and water vapor

Nanocrystalline coating with the same chemical composition as the nickel-based superalloys was proved to possess high resistance to oxidation and scale spallation, meanwhile avoid notable elements interdiffusion. It opens up a new direction for the development of protective coatings. However, in a worse environment containing chlorine and water vapor, the ultrafine grains act like a double-edged sword, which can promote the formation of a protective scale of Al2O3 or Cr2O3, but also favor the inward diffusion of Cl and H2O to accelerate corrosion. In order to solve this problem, moderate amount of oxygen was doped into nanocrystalline coating during magnetron sputtering. Then, corrosion behavior of the two nanocrystalline coatings with or without oxygen doping was studied in the O2 + 38% H2O environment with solid NaCl deposit. Results indicated that the doped oxygen can attract active elements of Ti and Al to form TiO2 and θ-Al2O3, which pinned at grain boundaries to keep the ultrafine grains stable at high temperature while prevent inward diffusion of the corrosive media. Accordingly, a dense and pure chromia scale was formed quickly at surface, ensuring that the oxygen-doped nanocrystalline coating provided the highest corrosion resistance under the synergy of solid NaCl deposit and water vapor. In contrast, the coating without oxygen doping suffered from severe internal corrosion.

Phosphate Chemical Use for Sequestration, Scale Inhibition, and Corrosion Control

Water utilities commonly dose phosphates to potable water to (1) reduce aesthetic problems by sequestration, (2) inhibit calcium carbonate scale formation via threshold inhibition, and (3) reduce corrosion of lead or copper plumbing materials by forming protective pipe scales. Despite widespread use and increasing importance of phosphates, significant gaps in fundamental understanding still exist. This is partly due to the proprietary nature of some phosphate chemicals, causing experimental data and acquired knowledge for public water supplies to be considered trade secrets. Here, we summarize the current state of the science, provide operational guidance, and identify knowledge gaps regarding the use of ortho- and polyphosphates. The goal is to empower water scientists to improve phosphate chemical performance and to avoid unintended adverse consequences.

Increasing access to water through flexible entitlements?

This article discusses 2 ideas for reforming abstraction of water from the natural environment in order to provide a balance between environmental protection and secure, sustainable access to water also for future generations. This matters in light of an increased risk of water scarcity and drought due to growth and a changing climate. The first of these ideas – a sliding scale of legal protection for abstractions seeks to match the strength of legal protection through the abstraction licence to how much water is abstracted, as well as to how critical to business use, and environmentally beneficial the abstraction is. The second idea – ‘bubble licensing’ – involves capping the amount of water available for abstraction in a catchment and to promote exchanges of water between abstractors, not just through trading, but also through reciprocity exchanges and bartering. This collective action approach is intended to transcend an individual fixed entitlement approach to abstracting water. The article develops its argument through an analysis of literature on water rights, pollution trading, water charges, as well as a reference to ongoing reform debates about abstraction licensing in England.

Effect of silicon on the formation of protective scale on Fe-10Ni-10Cr-4Al alloy pre-oxidized at low oxygen pressure

Effect of silicon on the formation of protective scale on Fe-10Ni-10Cr-4Al alloy pre-oxidized at low oxygen pressure

Effect of pressure on high-temperature oxidation of Ni alloys in supercritical CO2 containing impurities

Direct supercritical CO2 (sCO2) power cycles require structural materials compatible with hot sCO2 containing high levels of water and oxygen impurities. Chromia-forming Ni-based superalloys, which are leading candidates at temperatures > 600 °C, have shown good compatibility in pure sCO2, however potential impurity effects are not well understood. Herein we exposed several commercial Ni-based alloys to 95%CO2-4%H2O-(1−3)%O2 at 750 °C and 0.1 or 20 MPa for 2500 h. Protective chromia scales formed in all cases. Nevertheless, water vapor-assisted oxide volatilization clearly occurred at high pressure. The volatilization rates decreased with time, but still represent a potentially serious compatibility issue in real, high-velocity, sCO2 systems.

Thickness Effects on Oxidation Behavior and Consequent γ’ Degradation of a High-Al Ni-Based Single Crystal Superalloy

High temperature oxidation is considered to play an essential role in the thickness debit effect on the creep rupture life of Ni-based single crystal (SC) superalloys. In order to clarify thickness effects, thin-walled specimens of different thickness (t = 0.1, 0.3, 1.0 mm) were prepared. Cyclic and isothermal oxidation tests of a high-Al Ni-based SC superalloy IC21 were carried out at 900 °C and 1100 °C in order to study the thickness effects on the oxidation behavior and consequent microstructural degradation. Thin-walled specimens of S01-N exhibited a good oxidation resistance when the protective scale-forming elements were enough in the matrix. Specimen thickness tuned the oxidation kinetics by changing the spallation behavior but had few influences on the thermodynamics. The easier stress relief via creep deformation in thin specimens is the main reason behind this phenomenon. Moreover, the obvious temperature effects on the multilayer oxide scales caused the different thickness-related spallation behaviors. Weaker microstructural degradation appeared and was further mitigated by reduced specimen thickness. Sufficient Al content is considered to be indispensable for the formation of protective α-Al2O3 scale with less degradation of matrix during the high temperature oxidation of thin-walled Ni-based SC superalloy castings.

Oxidation-Limited Lifetime of ODS-FeCrAl Alloys: Observations on Influence of Surface Shape

Oxide dispersion-strengthened (ODS) FeCrAl ferritic steels constitute a class of alloys with a combination of mechanical strength capabilities and environmental resistance that permits operation at temperatures significantly higher than available classes of wrought alloy. A significant issue for these ODS alloys is that, because of the extreme operating temperatures, unexpected failure of the protective scale in service could lead to catastrophic degradation of high-temperature, high-pressure components. In the absence of handbook data for quantification of their high-temperature environmental degradation, significant efforts have been made to develop approaches for predictive oxidation lifetime modeling. The main basis for such models is an aspect of oxidation behavior peculiar to these alloys at very high temperatures, specifically, their ability to maintain a protective alumina scale until practically all available Al in the alloy has been consumed. At the high temperatures involved the concentration profile for Al throughout the component remains flat while the alumina scale is intact, so that knowledge of the oxidation kinetics provides a basis for calculating the time to exhaustion of the alloy’s Al reservoir, hence service life. Difficulties arise when unanticipated gradients in the Al concentration profile are introduced following, for instance, premature local mechanical failure of the protective scale. The intent of this work was to consider if and how scale failures change with differences in surface shape, and how related mechanistic understanding of the actual oxidation behavior may be used to extend the utility of the modeling approaches. Experimental results for coupons of different shapes were very largely in agreement with the basic tenets of the lifetime modeling approaches, but a notable finding was that cylindrical shapes reproducibly exhibited a reduction in unexpected early scale failures, leading to more consistent oxidation-limited lifetimes.

A Study on the Characteristics of Buds and Flowers in Pomegranate: Differences among Cultivars

The growing cultivation of pomegranate and the interest of consumers in the nutraceutical properties of the fruit have not yet spurred similar increases in the knowledge base of some important botanical and physiological aspects of this species, such as bud differentiation. The aim of this research was to study the bud morphology of four pomegranate cultivars (‘Comune S. Giorgio’, ‘Wonderful’, ‘Ki-Zakuro’, and ‘Haku Botan’) to better clarify the bud differentiation process. In all four cultivars, the number and the position of the buds were variable, from a typical two buds per node to a single bud or more (3). Two types of buds were observed: small and thin on the twigs (short, medium, and long) and large and round on the spurs; large buds were also observed on twigs but in a reduced number. Flowers showed differences among the cultivars, with a larger number of petals in ‘ornamental’ cultivars because of the petaloidy. Hermaphrodite flowers were larger and longer than the staminate flowers and also more abundant. Moreover, flowers developing from a flower bud were longer than flowers developing from mixed buds. The presence of an undifferentiated meristem, starch grains in the protective scales, and two small transition leaves were observed in all the types of buds from summer to the end of endodormancy in all cultivars. However, a dome-shaped meristem was observed in a few flower buds. Our observations indicate pomegranate behaves as a species for warm, sub-tropical, and tropical areas more than for temperate ones.

Reactive air aluminizing of a nickel-based superalloy (IN738LC): Coating formation mechanism

Reactive air aluminizing (RAA) based on a slurry route is a low-cost method with high efficiency to form aluminide coatings on surfaces where final coating microstructures are temperature and time-dependent. This study aims to incorporate the RAA method into standard heat-treatment cycles of IN738LC. Painted samples are solutionized, solutionized then aged, and only aged. Different samples are prepared at different stages of aluminide formation. FE-SEM surface morphology, BSE-SEM cross-sectional observations, surface XRD characterization, and comparing EDS elemental composition with Al-Ni-Cr phase diagrams are utilized to discuss the formation mechanism thoroughly. A classical high activity type of aluminide coatings with a triple-layered structure of β-NiAl and Cr-rich precipitates at the top coat, β-NiAl in the middle coat, and an IDZ is formed by the RAA method. A three-stage formation mechanism, including the reactive stage (interaction between molten Al and solid substrate), Al-inward diffusion at low and Ni-outward, and Al-inward diffusions at high temperatures, is proposed in detail. After heat-treatment cycles, a ~3 μm aluminum oxide protective scale is detected on the sample surfaces. γ-Al2O3 and α-Al2O3 are formed during only aging at 845 °C and solutionizing at 1120 °C on sample surfaces, respectively.

Development and Validation of the Adolescent and Children in Risk of Abuse and Maltreatment Protective Factors Scale (ACRAM-PFS)

BackgroundChild maltreatment is a significant global problem concerning over 25% of children around the world. Traditionally, the assessment of children’s welfare was characterized by the creation of instruments and models from the deficit-based theoretical framework.PurposeThis study aims to develop an instrument to measure protective factors (the Adolescent and Children Risk of Abuse and Maltreatment Protective Factors Scale, ACRAM-PFS) and gather evidence on its psychometric properties. ACRAM-PFS is an 18-items scale for the assessment of protective factors of child maltreatment developed from the socioecological framework.MethodStructural validity, reliability and convergent-related validity were studied for this measure in a sample of 616 children and adolescents, with age ranging from 0 to 18 years old (M = 12.14; SD = 5.22). Cases were informed by 286 child welfare workers. The sample was split in two subsamples, one to perform an Exploratory Factor Analysis (EFA) and the second to perform a Confirmatory Factor Analysis (CFA).ResultsThe CFA corroborate the three-factor structure that includes the children and adolescents’ resources, the family/caregiver’s resources and the community resources (χ2 = 278.005, df = 132, p < .001, CFI = 0.955, SRMR = .084, RMSEA = .061, [90% CI: .051-.071]). Results of convergent-related validity indicated significant correlation with CTQ-SF and protective factors dimension of C-CAPS.DiscussionThe results support that ACRAM-PFS is a rigorous measure for assessing protective factors for child maltreatment. The scale can serve as a key tool for designing strengths-based intervention strategies tailored to the actual needs of children and adolescents. The present study provides the implications for the development of protective factor scales in the field of child welfare.

Alterations induced by Tortrimosaica polypodivora on the stems of Microgramma vacciniifolia: simple or complex galls?

Abstract Microgramma vacciniifolia, an epiphyte fern, hosts of two stem galls. One is induced by Tortrimosaica polypodivora (Lepidoptera), which can also induce galls in M. squamulosa and M. mortoniana. The alterations induced by T. polypodivora on M. vacciniifolia stem were compared to non-galled organs to evaluate the anatomical potentials of host ferns in response to a galling Lepidoptera. Histochemical and histometrical comparisons between galled and non-galled stems were performed to assess the processes leading to gall formation. M. vacciinifolia and M. squamulosa galls were anatomically similar, although their sizes differ, reflecting the growth potential of each host species. Simple structural alterations, such as hyperplasia of cortical and pericycle cells, occur during gall formation, while cell hypertrophy, common in more complex galls, was only detected on the pericycle. Meristele size remained unaltered in galls, but the pericycle appeared hyperplasic. The protective scales were broader in galls. A nutritive tissue with lipids, typical to Lepidoptera galls, was observed around the larval chamber, with small cells and meristematic activity. Starch, proteins, and reducing sugars accumulated in nutritive cells are uncommonly found in Lepidoptera galls. Despite simple structural alterations, T. polypodivora induced a gradient of primary metabolites, similar to angiosperm galls.

Hot corrosion effect of the vacuum arc melted (a2/γ)Ti-48Al-2Nb-0.7Cr-0.3Si alloy under an environment of NaCl-Na2SO4 salt

The Ti-48Al-2Nb-0.7Cr-0.3Si alloy comprising of α2-Ti3Al and γ-TiAl phases was successfully fabricated using vacuum arc melting. To study its hot corrosion behaviour, the alloy was subjected to cyclic thermal loading under a Na2SO4 + 25wt.%NaCl molten salt mixture at 900 °C for up to 60 h. Mass change per unit surface was measured to determine the corrosion kinetics of the alloy. The alloy experienced severe hot corrosion attacks up to -50.94 mg/cm2. SEM indicated the formation of a mixture of TiO2/Al2O3 scales on the alloy's surface. XRD confirmed the presence of hot corrosion products such as Na2Ti3O7, TiO2, Al2O3, and Cr2O3. The presence of chlorine gas in the hot corrosion environment resulted in the delamination of the protective scale on the surface, indicating its detrimental effect.

Factor structure and psychometric proprieties of the COVID-19 prevention behaviours (COV19-PB) scale.

We sought to test the COVID19-PB scale's psychometric properties and its dimensionality in a sample composed of 1107 Italian adults aged from 18 to 80 years (M = 39.59; SD = 16.36), 75% (n = 830) females, and 25% (n = 277) males. Exploratory, Confirmatory factor analysis and parallel analysis were used to validate the instrument that resulted from the Ebola Virus protective behaviours scale adaptation. Fear of covid-19 and a 1-item level of adherence to the Covid-19 protection scale were used to test the measure's convergent validity. A four-factor structure emerged from exploratory and confirmatory factor analysis: direct avoidance, avoidance of public spaces, avoidance of social interaction, and talking about the virus as protection. COVID-19PB was a valuable measure to assess individuals' competencies in assuming correct behaviours during the pandemic.

Structural and electrochemical properties of scales formed on steel surface in CO2-rich brine at high pressure

The corrosion of API L80 steel used for oil wellbore is investigated in CO2-rich brine at high pressure and temperature. The effect of protective corrosion scales associated with different variables in CO2 environments is also discussed. Analyses of corrosion products formed on steel surface is conducted using FE-SEM/EDS, Raman spectroscopy and XRD. Potentiodynamic polarization and EIS are performed on corroded specimens and electrical equivalent circuit is proposed to describe the behavior of scales. Mass loss tests conducted on specimens corroded at 50 °C and 90 °C in brine saturated with CO2 at 15 MPa showed that corrosion rates are higher at lower temperatures. The scales formed on the steel surface are predominantly composed of FeCO3 enriched with calcium. The electrochemical protective performance of the scales is enhanced with increasing temperature. It was concluded that a long-term satisfactory performance of the scale also depends on the time and temperature of exposure to CO2 environment.

The Oxidation Properties of a NiCrAlY Coating Fabricated by Arc Ion Plating

The microstructures, phase compositions, and high-temperature oxidation behavior of a NiCrAlY coating fabricated by arc ion plating were investigated by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), atomic force microscope (AFM), and X-ray diffractometer (XRD). The results indicate that the NiCrAlY coating was covered by a protective Al2O3 scale with excellent oxidation resistance after oxidation at 1050 °C for 100 h; the β phase rich in Al in the as-deposited coating was transformed into a γ/γ’ phase; the interdiffusion zone (IDZ), secondary reaction zone (SRZ), and needle-like TCP phases were detected in the superalloy substrate beneath the coating.