scholarly journals Rapid Alloy Surface Engineering through Closed-Vessel Reagent Pyrolysis

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1764
Author(s):  
Cyprian Illing ◽  
Zhe Ren ◽  
Anna Agaponova ◽  
Arthur Heuer ◽  
Frank Ernst
Keyword(s):  
Gas Phase ◽  
Surface Engineering ◽  
Surface Film ◽  
Alloy Surface ◽  
Second Phase ◽  
Closed Vessel ◽  
Laboratory Equipment ◽  
Carbon And Nitrogen ◽  
Subsurface Zone ◽  
Gas Atmosphere

For rapid surface engineering of Cr-containing alloys by low-temperature nitrocarburization, we introduce a process based on pyrolysis of solid reagents, e.g., urea, performed in an evacuated closed vessel. Upon heating to temperatures high enough for rapid diffusion of interstitial solute, but low enough to avoid second-phase precipitation, the reagent is pyrolyzed to a gas atmosphere containing molecules that (i) activate the alloy surface by stripping away the passivating Cr2O3-rich surface film (diffusion barrier) and (ii) rapidly infuse carbon and nitrogen into the alloy. We demonstrate quantitatively that this method can generate a subsurface zone with concentrated carbon and nitrogen comparable to what can be accomplished by established (e.g., gas-phase- or plasma-based) methods, but with significantly reduced processing time. As another important difference to established gas-phase processing, the interaction of gas molecules with the alloy surface can have auto-catalytic effects by altering the gas composition in a way that accelerates solute infusion by providing a high activity of HNCO. The new method lends itself to rapid experimentation with a minimum of laboratory equipment.

Current Status of Supersaturated Surface Engineered S-Phase Materials

2008 ◽  
Vol 373-374 ◽  
pp. 289-295 ◽  
Author(s):  
Thomas Bell
Keyword(s):  
Phase Formation ◽  
Surface Engineering ◽  
S Phase ◽  
Scientific Development ◽  
Current Status ◽  
Essential Requirement ◽  
Carbon And Nitrogen ◽  
Supersaturated Solid Solutions ◽  
Fcc Structure ◽  
Microstructural Studies

The present paper reviews the scientific development of our understanding of S-Phase. It is now known that S-Phase formation is an example of para equilibrium phenomena. A necessary but not sufficient condition for S-Phase formation is the presence of an fcc structure at least in part with structure in the starting alloy. An essential requirement is for a nitride forming element to be present particularly Cr. After surface engineering with carbon, nitrogen or carbon and nitrogen to generate supersaturated solid solutions, the various tribological, corrosion, mechanical and microstructural studies are reviewed for the various alloy systems. The current industrial status of S-Phase technology on an international basis is examined and the potential for its acceptance in china is discussed.

An Integrated Approach to Geological Disposal of UK Wastes Containing Carbon-14

2013 ◽  
Author(s):  
Sarah Vines ◽  
David Lever
Keyword(s):  
Radioactive Waste ◽  
Gas Phase ◽  
Alternative Treatment ◽  
Phase 1 ◽  
Project Team ◽  
Waste Stream ◽  
Second Phase ◽  
Geological Disposal ◽  
Carbon 14 ◽  
Design Options

Carbon-14 is a key radionuclide in the assessment of the safety of a geological disposal facility for radioactive waste because of the calculated assessment of the radiological consequences of gaseous carbon-14 bearing species [i]. It may be that such calculations are based on overly conservative assumptions and that better understanding could lead to considerably reduced assessment of the radiological consequences from these wastes. Alternatively, it may be possible to mitigate the impact of these wastes through alternative treatment, packaging or design options. The Radioactive Waste Management Directorate of the UK’s Nuclear Decommissioning Authority (NDA RWMD) has established an integrated project team in which the partners are working together to develop a holistic approach to carbon-14 management in the disposal system [ii]. For a waste stream containing carbon-14 to be an issue: • There must be a significant inventory of carbon-14 in the waste stream; AND • That waste stream has to generate carbon-14 bearing gas; AND • A bulk gas phase has to entrain the carbon-14 bearing gas: AND • These gases must migrate through the engineered barriers in significant quantities; AND • These gases must migrate through the overlying geological environment (either as a distinct gas phase or as dissolved gas); AND • These gases must interact with materials in the biosphere (i.e. plants) in a manner that leads to significant doses and risks to exposed groups or potentially exposed groups. The project team has developed and used this “AND” approach to structure and prioritise the technical work and break the problem down in a manageable way. We have also used it to develop our approach to considering alternative treatment, packaging and design options. For example, it may be possible to pre-treat some wastes to remove some of the inventory or to segregate other wastes so that they are removed from any bulk gas phase which might facilitate migration through the geosphere. Initially, the project team has undertaken a six month programme of work to examine the current understanding of these aspects and has captured this in the Phase 1 report [ii], in a modelling basis spreadsheet and in scoping assessments, which help us better understand the potential significance of carbon-14. Using the current modelling basis, but ignoring any potential benefits from the geosphere in retarding or preventing gas from reaching the surface, the calculated release of carbon-14 is dominated by: corrosion of irradiated reactive metals (in the operational and early post-closure time frame); corrosion of irradiated stainless steel and leaching of irradiated graphite (in the longer term). The Phase 1 work has shown that there is considerable scope for reducing the calculated radiological consequence for these wastes and a roadmap has been developed for a second Phase of work.

Magnesium Corrosion in Different Solutions

2011 ◽  
Vol 690 ◽  
pp. 369-372 ◽  
Author(s):  
Nor Ishida Zainal Abidin ◽  
Darren Martin ◽  
Andrej Atrens
Keyword(s):  
Room Temperature ◽  
Surface Film ◽  
Mg Alloys ◽  
Second Phase ◽  
Corrosion Mechanism ◽  
Nacl Solution ◽  
Second Phases ◽  
Hank’S Solution ◽  
Protective Surface Film ◽  
Extra Resistance

The corrosion mechanism of Mg alloys in Hank’s solution was elucidated by comparing the corrosion of typical Mg alloys (AZ91, ZE41 and Mg2Zn0.2Mn) and high purity Mg in Hank’s solution at room temperature and in 3% NaCl saturated with Mg(OH)2. Corrosion was characterised by the evolved hydrogen and the surfaces after the immersion tests. Corrosion in Hank’s solution was weakly influenced by microstructure in contrast to corrosion in the 3% NaCl solution, where second phases cause strong micro-galvanic acceleration. This is attributed to the formation of a more protective surface film in Hank’s solution, causing extra resistance between the alpha-Mg matrix and the second phase. The incubation period in Hank’s solution was alloy dependent.

The effect of natural convection on the gas-phase Sal'nikov reaction in a closed vessel

2004 ◽  
Vol 6 (8) ◽  
pp. 1687 ◽  
Author(s):  
S. S. S Cardoso ◽  
P. C. Kan ◽  
K. K. Savjani ◽  
A. N. Hayhurst ◽  
J. F. Griffiths
Keyword(s):  
Natural Convection ◽  
Gas Phase ◽  
Closed Vessel

Influence of Laser Parameters on Magnesium Alloy Surface Modification

2011 ◽  
Vol 704-705 ◽  
pp. 1216-1218
Author(s):  
Kai Sun ◽  
Sen Yang ◽  
Feng Xia Liu
Keyword(s):  
Corrosion Resistance ◽  
Surface Modification ◽  
Magnesium Alloy ◽  
Laser Power ◽  
Surface Engineering ◽  
Laser Surface ◽  
Alloy Surface ◽  
Technological Parameters ◽  
Az91d Magnesium Alloy ◽  
Surface Modified

It’s an important content to treat on the magnesium alloy surface for improving it’s abrasion performance and corrosion resistance in the field of surface engineering nowerdays. This research takes the AZ91D magnesium alloy and Aluminum as a substrate and powdered alloy respectively.It takes the laser surface modified technology as the method so that to enhance the corrosion resistance of the magnesium alloy surface.The optimization technological parameters are obtained by discussing the influence rule on laser power to corrosion resistance of AZ91D substrate and Mg-Al modified level.

Comparative Tribocorrosion Resistance in Physiological Solution of Untreated and Modified Ti-6Al-4V Alloy Surface by Electrodeposition of Hydroxyapatite Coatings into Nanoporous Titania Layers

2016 ◽  
Vol 1139 ◽  
pp. 64-68
Author(s):  
Eliza Dănăilă ◽  
Lidia Benea
Keyword(s):  
Biomedical Applications ◽  
Surface Engineering ◽  
Physiological Solution ◽  
Alloy Surface ◽  
Fluid Solution ◽  
Medical Implants ◽  
Hard Tissue ◽  
Hydroxyapatite Coatings ◽  
Titania Layer ◽  
Metallic Biomaterial

Metallic biomaterial are the most suitable for replacing failed hard tissue up to now and for that is important to know the tribocorrosion resistance of these materials before use in biomedical applications. Surface engineering can play a significant role in extending the performance of medical implants made of titanium and its alloys. In this work was chosen electrodeposition of hydroxyapatite (HA) coatings into nanoporous titania layer formed by anodic oxidation as modified Ti-6Al-4V alloy surface. The comparative tribocorrosion behavior of untreated Ti-6Al-4V alloy surface, anodic nanoporous TiO2 surface and electrodeposited hydroxyapatite (HA) coatings into nanoporous TiO2 layers has been investigated in a bio-simulated fluid solution. The results of these investigations have shown that both surface treatments applied have improved the tribocorrosion resistance and friction coefficients as compared to the untreated Ti–6Al–4V alloy surface.

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