Origin of the Significant Impact of Ta on the Creep Resistance of FeCrNi Alloys

Heat resistant FeCrNi alloys are widely used in the petrochemical industry because they exhibit a unique combination of creep and oxidation resistance at temperatures exceeding 900$^\circ$C. Their creep properties are often optimized by micro-additions of carbide forming elements. In the present work, the influence of Ta micro-additions has been experimentally investigated both on as-cast and aged microstructures to understand the origin of the significant impact of this element on the creep resistance. Calculations with thermocal software were also carried out to support experimental data. It is shown that a small addition of Ta is beneficial as it increases the volume fraction of stable MC carbides. We demonstrate also that additions of Ta may have a dramatic effect on the thermal stability of microstructures. This is attributed to a smaller equilibrium volume fraction of M23C6 and more pronounced heterogeneous precipitation at MC/matrix interfaces. The influence on the creep properties in then discussed

Utjecaj Nb i Ti na mikrostrukturu i mehanička svojstva lijevanog čelika 30 % Ni / 18 % Cr nakon žarenja

The study discusses the microstructure and mechanical properties of eight tested 0.3 % C -30 % Ni - 18 % Cr cast steels stabilized with niobium and titanium after annealing in the cycle of 900 °C / 300 h. The niobium content in the cast steels varied from 0.0 to 2.0 % and that of titanium from 0.0 to 1.2 % by weight. Microstructure was examined using both light microscope and a scanning electron microscope with Link IS-IS attachement as well as an X-ray diffractometer. Depending on the chemical composition of cast steel, the following phases were identified: carbides of MC and M23C6 type and a phase rich in silicon, nickel, niobium and / or titanium, which was supposed to be a phase G. Relationships between the microstructure and mechanical properties of cast steel at 20 and 900 °C were examined as well.Studija raspravlja o mikrostrukturi i svojstvima osam testiranih lijevanih čelika - 0,3% C, 30 % Ni, 18 % Cr stabiliziranih niobijem i titanijem nakon žarenja u ciklusu od 900 °C / 300 h. Težinski udio niobija u lijevanim čelicima je varirao od 0,0 do 2,0 % a titanija od 0,0 do 1,2 %. Mikrostruktura se ispitivala i svjetlosnim mikroskopom i skener-elektronskim mikroskopom s priključkom na link IS-IS kao i na rentgenski difraktometar. Ovisno o kemijskom sastavu lijevanog čelika, identificirane su slijedeće faze: karbidi tipa MC i M23C6 i faze bogate silicijem, niklom, niobijem i / ili titanijem, a koju se smatra da je faza G. Također se ispitivao i odnos između mikrostrukture i mehaničkih svojstava lijevanog čelika na temperaturi od 20 i 900 °C

Measurements of Gas Pressure into the MV Arc Plasma Environment

Current interrupters equipped with arc quenching system based on combination of forced air flow and gassing material were the object of the research described in this paper. Arc quenching gas pressure inside the extinguishing chamber in direct vicinity of plasma arc was recorded by means of developed measurement system resistant for heavy duty conditions existent inside the chamber during breaking. Gas pressure was estimated for several values of load current at 12/24 kV source voltage

Prev Chronic Dis

IntroductionThe objective of this cross-sectional study was to examine the nutrition literacy status of adults in the Lower Mississippi Delta.MethodsSurvey instruments included the Newest Vital Sign and an adapted version of the Health Information National Trends Survey. A proportional quota sampling plan was used to represent educational achievement of residents in the Delta region. Participants included 177 adults, primarily African Americans (81%). Descriptive statistics, \ucf\u20212 analysis, analysis of variance, and multivariate analysis of covariance tests were used to examine survey data.ResultsResults indicated that 24% of participants had a high likelihood of limited nutrition literacy, 28% had a possibility of limited nutrition literacy, and 48% had adequate nutrition literacy. Controlling for income and education level, the multivariate analysis of covariance models revealed that nutrition literacy was significantly associated with media use for general purposes (F = 2.79, P = .005), media use for nutrition information (F = 2.30, P = .04), and level of trust from nutrition sources (F = 2.29, P = .005). Overall, the Internet was the least trusted and least used source for nutrition information. Only 12% of participants correctly identified the 2005 MyPyramid graphic, and the majority (78%) rated their dietary knowledge as poor or fair.ConclusionCompared with other national surveys, rates of limited health literacy among Delta adults were high. Nutrition literacy status has implications for how people seek nutrition information and how much they trust it. Understanding the causes and consequences of limited nutrition literacy may be a step toward reducing the burden of nutrition-related chronic diseases among disadvantaged rural communities