scholarly journals Investigation of CoCr Dental Alloy: Example from a Casting Workflow Standpoint

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 849
Author(s):  
Dragana Majerič ◽  
Vojkan Lazić ◽  
Peter Majerič ◽  
Aleksa Marković ◽  
Rebeka Rudolf
Keyword(s):  
Chromium Oxide ◽  
Silicon Oxide ◽  
Casting Process ◽  
Elemental Content ◽  
Dental Alloy ◽  
Cobalt Chromium ◽  
Alloy Matrix ◽  
X Ray ◽  
Cocr Alloy ◽  
The One

Cobalt-chromium (CoCr) alloys have been used in dentistry for dental bridges, crowns and implants for decades. When using CoCr alloys, a number of fractures have occurred in the Dental Laboratory, both when handling the castings and after they have been placed in the patient’s mouth. It is assumed that the key cause of the resulting fractures of CoCr dental bridges is the casting process, which includes the preparation and mixing of the basic components of the CoCr dental alloy, unstable solidification and the final treatment of the tooth casting surface. The aim of this study was, therefore, to examine three castings differently prepared from the CoCr alloy. For the initial CoCr alloy, we selected the one supplied directly from the manufacturer; three test samples were CoCr alloy remelted four times in the same crucible, while the fourth sample was the remaining solidified alloy from the crucible, taken at the last remelting. Characterisation of the microstructure of all four samples was performed by optical and scanning electron microscopy equipped with an energy dispersive X-ray spectroscope and X-ray diffractometry. Microhardness measurements were also performed. The investigation revealed that the microstructure of the castings is composed of a CoCr alloy matrix with a eutectic interdendritic composition and interdendritic precipitates, which were rich in W and Mo. The two oxides were identified as chromium oxide with silicon content and chromium oxide, which originated from the CoCr alloy as casting residue. The high content of silicon in the chromium oxide can be attributed to the silicon oxide from the ceramic melting crucible, mixed in with the remains from the CoCr alloy melting. The second oxide showed a more regular elemental content for chromium oxide, mixed with a small quantity of impurities and the casting CoCr alloy. Based on this research, some recommendations were made for working with CoCr alloys in the Dental Laboratory, with the aim of reducing the risk of dental bridge fractures in the future.

Detailed Studies on the High Temperature Corrosion Reactions between Potassium Chloride and Metallic Chromium

2011 ◽  
Vol 696 ◽  
pp. 218-223 ◽  
Author(s):  
Juho Lehmusto ◽  
Patrik Yrjas ◽  
Bengt Johan Skrifvars ◽  
Mikko Hupa
Keyword(s):  
Potassium Chloride ◽  
Chromium Oxide ◽  
Alkali Metals ◽  
Potassium Dichromate ◽  
Potassium Chromate ◽  
Detailed Knowledge ◽  
Tube Material ◽  
X Ray ◽  
The One ◽  
Alkali Chlorides

Recovery of energy from biomass and various waste–derived fuels by combustion has become important due to reduction of detrimental CO2 emissions. Biomass does, however, release significant amounts of chlorine and alkali metals, as e.g. HCl(g), KCl(g), KOH(g) and NaCl(g), into the gas phase during combustion. The alkali chlorides may cause deposits on superheater tubes, which interfere with operation and can lead to corrosion and/or blockage of the gas path. To prevent and diminish the problems mentioned above, better and more detailed knowledge of the reactions between potassium chloride and the tube materials during combustion is needed. These materials commonly contain, among other metals, chromium, which is thought to protect the rest of the material since it forms a very dense but thin oxide layer on the surface of the tube material. It has been suggested that the reaction between solid or partly molten KCl and chromium oxide is the one responsible for starting the complex series of corrosion reactions. In this work, the overall reaction between potassium chloride and chromium was studied through partial reactions with compounds known to participate to the overall reaction or to be formed during it. The reactions were studied in synthetic air by heating sample mixtures in a DTA/TGA (Differential Thermal Analysis/ Thermogravimetric Analysis) apparatus. Selected samples were also studied and analyzed with a scanning electron microscope equipped with an energy dispersive x-ray analyzer (SEM/EDXA). Under the used conditions both potassium chloride and potassium chromate reacted with pure chromium and chromium oxide. In the case of chromium, chromium oxide was formed via the formation of potassium chromate. In reactions including chromium oxide as reactant also potassium dichromate was detected.

scholarly journals Electrochemical Oxidation of Ti15Mo Alloy—The Impact of Anodization Parameters on Surface Morphology of Nanostructured Oxide Layers

Nanomaterials ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 68
Author(s):  
Magdalena Jarosz ◽  
Leszek Zaraska ◽  
Marcin Kozieł ◽  
Wojciech Simka ◽  
Grzegorz D. Sulka
Keyword(s):  
Surface Morphology ◽  
Pure Titanium ◽  
Elemental Content ◽  
Potential Range ◽  
Oxide Layers ◽  
X Ray ◽  
Nanostructured Oxide ◽  
One Step ◽  
The One ◽  
The Impact

It is well-known that the structure and composition of the material plays an important role in the processes occurring at the surface. In this paper, a surface morphology of nanostructured oxide layers electrochemically grown on Ti15Mo, tuned by applying different anodization parameters, was investigated in detail. The one-step anodization of Ti15Mo alloy was performed at room temperature in an ethylene glycol-based electrolyte containing 0.11 M NH4F and 1.11 M H2O. Different anodization times (ranging from 5 to 60 min) and applied potentials (40–100 V) were tested, and the surface morphology, elemental content, and crystalline structure were monitored by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffractometry (XRD), respectively. The results showed that contrary to the multistep anodization of titanium foil, the surface morphology of anodic oxide obtained via the one-step process contains the nanoporous outer layer covering the nanotubular structure. What is more, the pore diameter (Dp) and interpore distance (Dint) of such layers exhibit different trends than those observed for anodization of pure titanium. In particular, at a certain potential range, a decrease in both Dp and Dint with increasing potential was observed. However, independently on the used anodization conditions, the elemental content of oxide layers remained similar, showing the amount of molybdenum at c.a. 15 wt.%. Finally, the amorphous nature of as-anodized layers was confirmed, and their optical band-gap was determined from the diffuse reflectance UV–Vis spectra. It was found that Eg is tunable to some extent by changing the anodizing potential. However, further thermal treatment in air at 400 °C resulted in the anatase phase formation that was accompanied by a significant Eg reduction. Therefore, we believe that the presented results will greatly contribute to the understanding of anodic formation of nanostructured functional oxide layers with tunable properties that can be applied in various fields.

DELORO STELLITE 25

Alloy Digest ◽  
2021 ◽  
Vol 70 (11) ◽  
Keyword(s):  
Wear Resistance ◽  
Corrosion Resistance ◽  
Base Alloy ◽  
Chromium Alloy ◽  
Cobalt Chromium ◽  
Alloy Matrix ◽  
Cobalt Base Alloy ◽  
Cocr Alloy ◽  
Cobalt Base ◽  
Cobalt Chromium Alloy

Abstract Deloro Stellite 25 is a cobalt-chromium-tungsten-nickel alloy. This tungsten strengthened cobalt-chromium alloy is the cast version of the wrought cobalt-base alloy L605. Deloro Stellite 25 is resistant to wear, galling, and corrosion and retains this resistance at high temperatures. Its exceptional wear resistance is due mainly to the unique inherent characteristics of the hard carbide phase dispersed in a CoCr alloy matrix. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as machining. Filing Code: Co-142. Producer or source: Deloro Wear Solutions GmbH.

scholarly journals Effects of Al2O3 Addition on the Microstructure and Properties of CoCr Alloys

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1074 ◽  
Author(s):  
Qin Hong ◽  
Peikang Bai ◽  
Jianhong Wang
Keyword(s):  
Structural Characteristics ◽  
Biological Properties ◽  
Elemental Distribution ◽  
Cobalt Chromium ◽  
X Ray ◽  
Al2o3 Addition ◽  
Columnar Grains ◽  
Alloy Microstructure ◽  
Cocr Alloy ◽  
Equiaxed Grains

Aluminum oxide (Al2O3) powder can be added to typical cobalt-chromium (CoCr) alloy powders. In the present study, we successfully prepared alloyed samples of various powder ratios by laser cladding and analyzed their microstructure and carbide structural characteristics, including the microhardness, biological properties, morphology (using scanning electron microscopy), and crystal structure (using X-ray powder diffraction). The elemental distribution was also determined by energy-dispersive X-ray spectroscopy. The results showed that an Al2O3 addition caused the alloy microstructure to change from slender columnar crystals to columnar grains that were similar in shape to equiaxed grains. In addition, Al2O3 agglomeration zones appeared, and carbide structures were altered. The mechanism of the observed performance changes was also analyzed.

Chemical partitioning of elements in Ni-base MC-carbide reinforced eutetic superalloys

1983 ◽  
Vol 41 ◽  
pp. 250-251
Author(s):  
E. F. Koch ◽  
E. L. Hall ◽  
S. W. Yang
Keyword(s):  
Alloy Composition ◽  
Volume Fraction ◽  
Lattice Mismatch ◽  
Turbine Blades ◽  
Eutectic Alloys ◽  
Alloy Matrix ◽  
X Ray ◽  
Gas Turbine Blades ◽  
Analytical Electron ◽  
Analytical Electron Microscope

The plane-front solidified eutectic alloys consisting of aligned tantalum monocarbide fibers in a nickel alloy matrix are currently under consideration for future aircraft and gas turbine blades. The MC fibers provide exceptional strength at high temperatures. In these alloys, the Ni matrix is strengthened by the precipitation of the coherent γ' phase (ordered L12 structure, nominally Ni3Al). The mechanical strength of these materials can be sensitively affected by overall alloy composition, and these strength variations can be due to several factors, including changes in solid solution strength of the γ matrix, changes in they γ' size or morphology, changes in the γ-γ' lattice mismatch or interfacial energy, or changes in the MC morphology, volume fraction, thermal stability, and stoichiometry. In order to differentiate between these various mechanisms, it is necessary to determine the partitioning of elemental additions between the γ,γ', and MC phases. This paper describes the results of such a study using energy dispersive X-ray spectroscopy in the analytical electron microscope.

Analytical Electron Microscopy Study of Second-Phase Particles in 7075 and 7475 Aluminum Alloys

1985 ◽  
Vol 43 ◽  
pp. 348-349
Author(s):  
M. Raghavan ◽  
J. Y. Koo ◽  
J. W. Steeds ◽  
B. K. Park
Keyword(s):  
Aluminum Alloys ◽  
Silicon Oxide ◽  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Partial Substitution ◽  
Second Phase ◽  
X Ray ◽  
Second Phase Particles ◽  
Almost All

X-ray microanalysis and Convergent Beam Electron Diffraction (CBD) studies were conducted to characterize the second phase particles in two commercial aluminum alloys -- 7075 and 7475. The second phase particles studied were large (approximately 2-5μm) constituent phases and relatively fine ( ∼ 0.05-1μn) dispersoid particles, Figures 1A and B. Based on the crystal structure and chemical composition analyses, the constituent phases found in these alloys were identified to be Al7Cu2Fe, (Al,Cu)6(Fe,Cu), α-Al12Fe3Si, Mg2Si, amorphous silicon oxide and the modified 6Fe compounds, in decreasing order of abundance. The results of quantitative X-ray microanalysis of all the constituent phases are listed in Table I. The data show that, in almost all the phases, partial substitution of alloying elements occurred resulting in small deviations from the published stoichiometric compositions of the binary and ternary compounds.

Preparation of cultured astrocytes for x-ray microanalysis

1989 ◽  
Vol 47 ◽  
pp. 988-989
Author(s):  
N.K.R. Smith ◽  
K.E. Hunter ◽  
P. Mobley ◽  
L.P. Felpel
Keyword(s):  
Cultured Cells ◽  
Elemental Content ◽  
Elemental Distribution ◽  
Sprague Dawley ◽  
X Ray ◽  
Cultured Astrocytes ◽  
Freeze Dried ◽  
Ultimate Objective

Electron probe energy dispersive x-ray microanalysis (XRMA) offers a powerful tool for the determination of intracellular elemental content of biological tissue. However, preparation of the tissue specimen , particularly excitable central nervous system (CNS) tissue , for XRMA is rather difficult, as dissection of a sample from the intact organism frequently results in artefacts in elemental distribution. To circumvent the problems inherent in the in vivo preparation, we turned to an in vitro preparation of astrocytes grown in tissue culture. However, preparations of in vitro samples offer a new and unique set of problems. Generally, cultured cells, growing in monolayer, must be harvested by either mechanical or enzymatic procedures, resulting in variable degrees of damage to the cells and compromised intracel1ular elemental distribution. The ultimate objective is to process and analyze unperturbed cells. With the objective of sparing others from some of the same efforts, we are reporting the considerable difficulties we have encountered in attempting to prepare astrocytes for XRMA.Tissue cultures of astrocytes from newborn C57 mice or Sprague Dawley rats were prepared and cultured by standard techniques, usually in T25 flasks, except as noted differently on Cytodex beads or on gelatin. After different preparative procedures, all samples were frozen on brass pins in liquid propane, stored in liquid nitrogen, cryosectioned (0.1 μm), freeze dried, and microanalyzed as previously reported.

scholarly journals Rapid classification of commercial teas according to their origin and type using elemental content with X-ray fluorescence (XRF) spectroscopy

2021 ◽  
Vol 4 ◽  
pp. 45-52
Author(s):  
Cia Min Lim ◽  
Manus Carey ◽  
Paul N. Williams ◽  
Anastasios Koidis
Keyword(s):  
Elemental Content ◽  
X Ray ◽  
Xrf Spectroscopy

scholarly journals Surface Analysis of Chamber Coating Materials Exposed to CF4/O2 Plasma

Coatings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 105
Author(s):  
Seung Hyun Park ◽  
Kyung Eon Kim ◽  
Sang Jeen Hong
Keyword(s):  
Photoelectron Spectroscopy ◽  
Yttrium Aluminum Garnet ◽  
Silicon Oxide ◽  
Ceramic Materials ◽  
High Plasma ◽  
Coating Materials ◽  
Continuous Increase ◽  
X Ray ◽  
Bonding Structure ◽  
Manufacturing Environments

Coating the inner surfaces of high-powered plasma processing equipment has become crucial for reducing maintenance costs, process drift, and contaminants. The conventionally preferred alumina (Al2O3) coating has been replaced with yttria (Y2O3) due to the long-standing endurance achieved by fluorine-based etching; however, the continuous increase in radio frequency (RF) power necessitates the use of alternative coating materials to reduce process shift in a series of high-powered semiconductor manufacturing environments. In this study, we investigated the fluorine-based etching resistance of atmospheric pressure-sprayed alumina, yttria, yttrium aluminum garnet (YAG), and yttrium oxyfluoride (YOF). The prepared ceramic-coated samples were directly exposed to silicon oxide etching, and the surfaces of the plasma-exposed samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. We found that an ideal coating material must demonstrate high plasma-induced structure distortion by the fluorine atom from the radical. For endurance to fluorine-based plasma exposure, the bonding structure with fluoride was shown to be more effective than oxide-based ceramics. Thus, fluoride-based ceramic materials can be promising candidates for chamber coating materials.

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