Functionalization of metallic powder for performance enhancement

The oxidation state and surface properties of powder particles play a major role in the final properties of powder manufactured components. In the present study, the coating of a non-stainless low alloy (SA508 Grade 3) steel powder was explored to protect it from progressive oxidation while also studying the effects on powder flowability and electrical charging. The protective coating was applied by magnetron sputtering of chromium. The surface chemistries of both as-received and Cr coated powders were studied using X-ray photo electron spectroscopy (XPS). Accelerated oxidation tests were carried out on both uncoated and Cr coated powders to study the effects of coating on oxidation resistance. Hard X-ray photoelectron spectroscopy (HAXPES) analysis was used to measure oxygen pick up near the surface, showing significant reductions for the case of the Cr coated powder. The conductivity of the powder was found to increase with Cr coating. The flowability of the powder was characterised by the tapped density, the angle of repose (AOR) and a powder rheometer, and it was found to improve with a Cr coating, which can be attributed to reduced tribo-electrical charging and reduced cohesivity of the powder particles

Evolution of grain boundary network topology in 316L austenitic stainless steel during powder hot isostatic pressing

The grain boundary network evolution of 316L austenitic steel powder during its densification by hot isostatic pressing (HIPing) was investigated. While the as-received powder contained a network of random high angle grain boundaries, the fully consolidated specimen had a large fraction of annealing twins, indicating that during densification, the microstructure evolves via recrystallization. By interrupting the HIPing process at different points in time, microstructural changes were tracked quantitatively at every stage using twin boundary fractions, distribution of different types of triple junctions, and the parameters associated with twin related domains (TRDs). Results revealed that, with increase in temperature, (i) the fraction of annealing twins increased steadily, but they mostly were not part of the grain boundary network in the fully consolidated specimen and (ii) the average number of grains within a TRD, the length of longest chain, and twinning polysynthetism increased during HIPing and (iii) the powder characteristics and the HIPing parameters have a strong influence on the development of grain boundary network. Based on the results obtained, possible alterations to the HIPing process are discussed, which could potentially allow twin induced grain boundary engineering

Solid State Phase Transformations in Uranium-Zirconium Alloys

Uranium-10wt% zirconium (U-10Zr) alloy nuclear fuels have been used for decades and new variations are under consideration ranging from U-5Zr to U-50Zr. As a precursor to understanding the fission gas behavior in U-Zr alloys using ion implantation, a basic study on the U-Zr metallurgy was completed using EPMA, DSC, XRD, Optical microscopy, and TEM with a focus on solid state phase transformations in alloys containing 2, 5, 10, 20, 30, and 50wt% zirconium. Alloys were cast by crucible melting using high temperature furnace under argon atmosphere in yttrium oxide crucibles and various thermal profiles were used to study phase transformations in these alloys. Using TEM, XRD, and DSC data, it was ascertained that athermal-ω, along with martensitic α1, formed in all alloys quenched from γ phase. XRD could detect the presence of athermal-ω only in U-20, 30 and 50wt%Zr alloys. BSE images for as-cast alloys of 2, 5, 10, 20, and 30wt%Zr had lamellar microstructure with lamellae rich in zirconium. All alloy samples clearly showed a heating transformation pertaining to δ → γ in DSC data while XRD could only confirm the presence of δ phase in U-20, 30, and 50wt%Zr alloys. An explanation is offered for the absence of δ phase peaks in uranium-rich alloys based on its formation mechanism. Alloy samples of U-2, 5, and 10wt%Zr were step-cooled from γ phase by annealing in the (α + δ) phase field before cooling to room temperature revealed broad peaks for δ phase indicating incomplete collapse of {111}γ planes. Both as cast and γ- quenched alloys were annealed at 600degreeC, in the (α + δ) phase field for 1, 3, 7, and 30 days. Microstructures of the samples in both cases contained uranium-rich matrix and zirconium-rich precipitates and WDS analyses were consistent with their being α-U and δ phase respectively. However, XRD data for annealed alloys never showed peaks for δ phase even though it’s area fraction was within the detection limits. Moreover, the peaks which were present in U-20wt%Zr vanished after annealing for 7 days. Based on the data obtained, it is suggested that it is more appropriate to consider the presence of metastable diffusional-ω instead of a stable δ in the as-cast alloys and that it is not stable at 600degreeC

Thermodynamic assessment of the uranium-zirconium alloy system for nuclear energy applications

Uranium – 10 wt% zirconium (U-10Zr) alloy nuclear fuels have been used for many decades and new variations are under consideration ranging from U-5Zr to U-50Zr. The thermophysical behavior of the uranium-zirconium system has been revisited using differential scanning calorimetry (DSC) and other methods. Alloys containing 0.1, 2, 5, 10, 20, 30, and 50 wt% zirconium were prepared by melt-casting ~40 g samples in yttrium oxide crucibles. The phase transitions observed using DSC analyses are in general agreement with the established phase diagram with a few notable exceptions that may, in part, be due to impurities. Most notably, the transition from the ??(U)+?? phase field to the ??(U)+?? phase field at ~662??C was never observed in these experiments. This observation is consistent with earlier experimental assessments of the U-Zr binary phase diagram as compared with the more recent computational assessments

Metallurgical characterization of the delta phase formation in uranium-zirconium alloy fuels

Uranium – 10 wt% zirconium (U-10Zr) alloy nuclear fuels have been used for many decades and new variations are under consideration ranging from U-5Zr to U-50Zr. As a precursor to studying fission gas behavior using ion implantation, a basic study of U-Zr metallurgy was completed. The initial focus was to clarify literature ambiguity regarding the formation of the UZr<SUB>2</SUB> delta phase. Sample alloys were created containing 0.1, 2, 5, 10, 20, 30, and 50 wt% zirconium. Initial structures were created via ???furnace-cooled??? and ???gamma-quenched??? temperature profiles. Samples of each composition and thermal profile were annealed under argon at 600??C for 24, 72, and 168 hours. Quantitative analyses were completed using an electron microprobe. The delta phase formed readily in annealed furnace-cooled samples whereas gamma-quenched samples exhibited sluggish transformations. The rate of cooling U-Zr alloys has a profound impact on the kinetics of delta phase formation

Decomposition of the ?? phase in as-cast and quenched U-Zr alloys

An investigation of the decomposition of the high temperature gamma phase in as-cast and quenched U-Zr alloys was conducted. Differential scanning calorimetry data clearly showed delta reversible arrow g transformations in alloys with <10 wt% Zr while XRD data did not contain any peaks which uniquely identify it's presence. Since delta phase forms via omega transformation, a comparison of the theoretical diffraction patterns for omega and delta revealed that the intensities of the peaks which uniquely identify the existence of delta when alpha-U is present, were either very weak, or were zero in omega, suggesting that the ambiguity can be explained if the phase present in these alloys is omega as opposed to delta. Our data are consistent with the presence of delta and omega in as-cast and quenched U-50Zr alloy, respectively, and (alpha+omega) in rest of the as-cast and quenched alloys. Based on the experimental data, the transformation sequence from gamma phase in U-Zr alloys is proposed.clos

Toiminnanohjausjärjestelmän kuvaaminen ja kehittäminen

Opinnäytetyön tavoitteena oli kuvata ja kehittää toimeksiantajaorganisaation toiminnanohjausjärjestelmää. Toimeksiantajana tutkimustyölle toimi Turussa sijaitseva Storm Motor Oy. Organisaation käytössä oli työn aikana vuoden 2007 Microsoft Business Solutions-Navision versio 4.00 SP3. Tutkintotyön aikana kuvattiin organisaation Turun toimipisteen myymälän, varaston sekä hankinnan toimintoja. Jokainen osa-alue käsiteltiin toiminnanohjausjärjestelmän käyttäjän näkökulmasta. Toiminnanohjausjärjestelmän toimintojen kuvaamisen lisäksi tutkimustyön ohella kuvattiin tärkeimmät organisaation toiminnot. Toiminnanohjausjärjestelmän kehittämisen lisäksi tutkintotyön ohessa suoritettiin kaksi kehitysprojektia organisaatiolle, jotka on liitetty tämän tutkintotyön yhteyteen. Opinnäytetyötä hyödynnetään tulevaisuudessa perehdytysmateriaalina henkilökunnalle.The main purpose of this thesis was to describe and develop the ERP-system used by the client. The client for this Thesis was Storm Motor Oy located in Turku. During the time of thesis organization was using Microsoft Business Solutions-Navision version 4.00 SP3 from the year 2007. During the thesis organizations store, warehouse and purchasing department were described from the ERP-system user’s point of view. Due to the nature of the thesis, most important operational functions of the organization were also described and recorded. In addition, two improvement projects were successfully completed during this thesis, which have been attached to this study. The thesis will be utilized in the future as an introductory material for the staff.Tutkintotyöhön on liitetty opinnäytetyön aikana kehitetty uudistettu kassalaskenta- ja seurantataulukko toimipisteiden käyttöön sekä reklamaatio-ohjeistus

Nature of Gallium Focused Ion Beam induced phase transformation in 316L austenitic stainless steel

AbstractThe microstructural evolution and chemistry of the ferrite phase (α), which transforms from the parent austenite phase (γ) of 316L stainless steel during gallium (Ga) ion beam implantation in Focused Ion Beam (FIB) instrument was systematically studied as a function of Ga+ ion dose and γ grain orientations. The propensity for initiation of γ → α phase transformation was observed to be strongly dependent on the orientation of the γ grain with respect to the ion beam direction and correlates well with the ion channelling differences in the γ orientations studied. Several α variants formed within a single γ orientation and the sputtering rate of the material, after the γ → α transformation, is governed by the orientation of α variants. With increased ion dose, there is an evolution of orientation of the α variants towards a variant of higher Ga+ channelling. Unique topographical features were observed within each specific γ orientation that can be attributed to the orientation of defects formed during the ion implantation. In most cases, γ and α were related by either Kurdjumov-Sachs (KS) or Nishiyama-Wassermann (NW) orientation relationship (OR) while in few, no known OR's were identified. While our results are consistent with gallium enrichment being the cause for the γ → α phase transformation, some observations also suggest that the strain associated with the presence of gallium atoms in the lattice has a far field stress effect that promotes the phase transformation ahead of gallium penetration