The Role of Copper in Resisting Metal Dusting of Ni-Base Alloys

2006 ◽  
Vol 522-523 ◽  
pp. 581-588 ◽  
Author(s):  
Yoshitaka Nishiyama ◽  
Nobuo Otsuka
Keyword(s):  
Oxide Scale ◽  
Metal Surfaces ◽  
Binary Alloys ◽  
Material Design ◽  
Coke Deposition ◽  
Metal Dusting ◽  
Cu Content ◽  
Pit Formation ◽  
A New Technique

The present study focuses on a new technique for the prevention of metal dusting in carbonaceous gas environments at intermediate temperature. Preliminary laboratory metal dusting test was conducted for Ni-x%Cu binary alloys and Ni-Cr alloys with various Si and Cu content in a simulated 60%CO-26%H2 -11.5%CO2-2.5%H2O (in vol.%) gas mixture at 650°C. Specimens of the binary alloys containing low Cu were entirely covered with coke and showed rough metal surfaces due to the degradation of metal. Alloys of 20% and more Cu, on the contrary, had no coke deposition and smooth metal surfaces, suggesting alloys with an adequate Cu do not react with CO in the syngas mixture without an oxide scale barrier. Based on these results, we conclude that Cu does not protect by formation of the oxide scale but has a “Surfactant-Mediated Suppression” against metal dusting. This effect can be explained in terms of atomistic interaction of CO with transition-metal surfaces by electronic structure analyses. For the Ni-Cr alloy, both addition of Si and Cu played a role of preventing pit formation in the simulated syngas atmosphere. The concept can be also useful for the practical material design of Ni-Cr-Si-Cu alloy with excellent metal dusting resistance.

scholarly journals The Effect of Cu Content and Surface Finish on the Metal Dusting Resistance of Additively Manufactured NiCu Alloys

2021 ◽  
Author(s):  
Katrin Jahns ◽  
Anke S. Ulrich ◽  
Clara Schlereth ◽  
Lukas Reiff ◽  
Ulrich Krupp ◽  
...  
Keyword(s):  
Surface Finish ◽  
Powder Bed Fusion ◽  
Metal Dusting ◽  
Laser Powder Bed Fusion ◽  
Roughness Measurement ◽  
Powder Bed ◽  
Cu Content ◽  
Binary Model ◽  
Interesting Candidate ◽  
Nicu Alloys

AbstractDue to the inhibiting behavior of Cu, NiCu alloys represent an interesting candidate in carburizing atmospheres. However, manufacturing by conventional casting is limited. It is important to know whether the corrosion behavior of conventionally and additively manufactured parts differ. Samples of binary NiCu alloys and Monel Alloy 400 were generated by laser powder bed fusion (LPBF) and exposed to a carburizing atmosphere (20 vol% CO–20% H2–1% H2O–8% CO2–51% Ar) at 620 °C and 18 bar for 960 h. Powders and printed samples were investigated using several analytic techniques such as EPMA, SEM, and roughness measurement. Grinding of the material after building (P1200 grit surface finish) generally reduced the metal dusting attack. Comparing the different compositions, a much lower attack was found in the case of the binary model alloys, whereas the technical Monel Alloy 400 showed a four orders of magnitude higher mass loss during exposure despite its Cu content of more than 30 wt%.

scholarly journals Getting ahead of the Arms Race: Hothousing the Coevolution of VirusTotal with a Packer

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 395
Author(s):  
Héctor D. Menéndez ◽  
David Clark ◽  
Earl T. Barr
Keyword(s):  
Machine Learning ◽  
Evolutionary Computation ◽  
Malware Detection ◽  
Cloud Service ◽  
False Positives ◽  
Arms Race ◽  
System Calls ◽  
A New Technique ◽  
Coevolutionary Arms Race

Malware detection is in a coevolutionary arms race where the attackers and defenders are constantly seeking advantage. This arms race is asymmetric: detection is harder and more expensive than evasion. White hats must be conservative to avoid false positives when searching for malicious behaviour. We seek to redress this imbalance. Most of the time, black hats need only make incremental changes to evade them. On occasion, white hats make a disruptive move and find a new technique that forces black hats to work harder. Examples include system calls, signatures and machine learning. We present a method, called Hothouse, that combines simulation and search to accelerate the white hat’s ability to counter the black hat’s incremental moves, thereby forcing black hats to perform disruptive moves more often. To realise Hothouse, we evolve EEE, an entropy-based polymorphic packer for Windows executables. Playing the role of a black hat, EEE uses evolutionary computation to disrupt the creation of malware signatures. We enter EEE into the detection arms race with VirusTotal, the most prominent cloud service for running anti-virus tools on software. During our 6 month study, we continually improved EEE in response to VirusTotal, eventually learning a packer that produces packed malware whose evasiveness goes from an initial 51.8% median to 19.6%. We report both how well VirusTotal learns to detect EEE-packed binaries and how well VirusTotal forgets in order to reduce false positives. VirusTotal’s tools learn and forget fast, actually in about 3 days. We also show where VirusTotal focuses its detection efforts, by analysing EEE’s variants.

Structural role of copper in the minerals of the pearceite-polybasite group: the case of the new minerals cupropearceite and cupropolybasite

2007 ◽  
Vol 71 (06) ◽  
pp. 641-650 ◽  
Author(s):  
L. Bindi ◽  
M. Evain ◽  
P. G. Spry ◽  
K. T. Tait ◽  
S. Menchetti
Keyword(s):  
Chemical Characterization ◽  
Sample Space ◽  
The Other ◽  
Crystal Chemical ◽  
Structural Position ◽  
Space Group ◽  
Cu Content ◽  
Own Name

Abstract The pearceite-polybasite group of minerals, general formula [M6T2S7][Ag9CuS4] with M = Ag, Cu; and T = As, Sb, show a crystal structure which can be described as the succession, along the c axis, of two pseudo-layer modules: a [M6T2S7]2– A module layer and a [Ag9CuS4]2+ B module layer. Copper is present in one structural position of the B module layer and replaces Ag in the only fully occupied M position of the A module layer. When the Cu content is >4.00 a.p.f.u., the structural position of the A module layer becomes Cu-dominant and, consequently, the mineral deserves its own name. In this paper we report the crystal-chemical characterization of two Cu-rich members exhibiting the 111 unitcell type (corresponding to the Tac polytype). One sample (space group (P )m1, a 7.3218(8), c 11.8877(13) Å, V 551.90(10) Å3, Z = 1) having As >Sb and with the structural position of the A module layer dominated by Cu, has been named cupropearceite and the other sample (space group (P3̄)m1, a 7.3277(3), c 11.7752(6) Å, V 547.56(8) Å3, Z = 1) having Sb >As has been named cupropolybasite. Both the new minerals and mineral names have been approved by the IMA-CNMNC.

The role of Cu content on structure and magnetic properties of Fe–Si–B–P–Cu nanocrystalline alloys

2018 ◽  
Vol 54 (5) ◽  
pp. 4400-4408 ◽  
Author(s):  
Xingjie Jia ◽  
Yanhui Li ◽  
Licheng Wu ◽  
Yan Zhang ◽  
Lei Xie ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Nanocrystalline Alloys ◽  
Cu Content

Trends in water-promoted oxygen dissociation on the transition metal surfaces from first principles

2017 ◽  
Vol 19 (3) ◽  
pp. 2364-2371 ◽  
Author(s):  
Ming Yan ◽  
Zheng-Qing Huang ◽  
Yu Zhang ◽  
Chun-Ran Chang
Keyword(s):  
Transition Metal ◽  
First Principles ◽  
Metal Surfaces ◽  
Oxygen Dissociation ◽  
Transition Metal Surfaces

The trend of O2 dissociation on the nine transition metal surfaces and the promotional role of water were systematically investigated.

scholarly journals A review of fungal influenced corrosion of metals

2021 ◽  
Vol 62 (4) ◽  
pp. 333-339
Author(s):  
Imo Okorie ◽  
Romanus Nwokorie
Keyword(s):  
Growth Pattern ◽  
Metal Surfaces ◽  
Structural Integrity ◽  
Great Influence ◽  
Fungal Growth ◽  
Corrosive Media ◽  
Electrochemical Processes ◽  
Single Mechanism ◽  
Growth Of Fungi

The growth of fungi on the surface of metals has great influence on their structural integrity and failure. Their growth on metal surfaces is determined by their secreted metabolites which enable them to adapt to new environmental and nourishment conditions. Although information on the capacity of fungi to adapt to metal surfaces is scarce, most fungi growing on metal surfaces alter the composition of the metals involving it in the process of functional growth and metabolism. Changes in the composition and colour of the metals are some of the evidences confirming that fungus has penetrated the metal surfaces and use it to satisfy its nutritional need with resultant corrosion. In this work we tried to explain different mechanisms of fungal influenced corrosion from different perspectives ranging from the role of biofilms, corrosive media generation by fungal metabolism processes to electrochemical processes generated by fungal growth on metal surfaces. Finally, no single mechanism can conclusively explain all forms of fungal influenced corrosion because every mechanism is unique and applies to individual fungus, its metabolic biproducts or the growth pattern.

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