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The corrosion resistance of laser surface alloyed stainless steels

Brytan Z.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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Vol. 91, nr 2

49--59

EN

Purpose: of this paper was to examine the corrosion resistance of laser surface alloyed (LSA) stainless steels using electrochemical methods in 1M NaCl solution and 1M H2SO4 solution. The LSA conditions and alloying powder placement strategies on the material's corrosion resistance were evaluated. Design/methodology/approach: In the present work the sintered stainless steels of different microstructures (austenitic, ferritic and duplex) where laser surface alloyed (LSA) with elemental alloying powders (Cr, FeCr, Ni, FeNi) and hard powders (SiC, Si3N4) to obtain a complex steel microstructure of improved properties. Findings: The corrosion resistance of LSA stainless steels is related to process parameters, powder placing strategy, that determines dilution rate of alloying powders and resulting steel microstructure. The duplex stainless steel microstructure formed on the surface layer of austenitic stainless steel during LSA with Cr and FeCr reveal high corrosion resistance in 1M NaCl solution. The beneficial effect on corrosion resistance was also revealed for LSA with Si3N4 for studied steels in both NaCl and H2SO4 solutions. Ferritic stainless steel alloyed with Ni, FeNi result in a complex microstructure, composed of austenite, ferrite, martensite depending on the powder dilution rate, also can improve the corrosion resistance of the LSA layer. Research limitations/implications: The LSA process can be applied for single phase stainless steels as an easy method to improve surface properties, elimination of porosity and densification and corrosion resistance enhancement regarding as sintered material. Practical implications: The LSA of single phase austenitic stainless steel in order to form a duplex microstructure on the surface layers result in reasonably improved corrosion performance. Originality/value: The original LSA process of stainless steels (austenitic, ferritic and duplex) was studied regarding corrosion resistance of the alloyed layer in chloride and sulphate solutions.

2

Leaching of manganese ores using corncob as reductant in H2SO4 solution

Ali S., Iqbal Y., Farooq U., Ahmad S.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 1

56--65

EN

In this study, corncob was used as reductant for sulfuric acid leaching of manganese ore from Daweezi, Upper Mohmand Agency, Pakistan. X-ray diffraction of representative powdered samples revealed the presence of manganese silicate MnSiO(SiO4), calcite (CaCO3), and -quartz (SiO2). X-ray diffraction and energy dispersive spectroscopy analyses indicated that the examined manganese ore was siliceous in nature. Three process parameters were investigated in the present study including the particle size of the ore, leaching temperature, and amount of corncob. Manganese extraction of 92.48 wt% was achieved for a leaching time of 60 min at 90 oC using 1.9 mol/dm3 H2SO4 concentration and 4 g of corncob. The present results demonstrated that corncob is a low cost, renewable, and non-hazardous reducing agent for manganese leaching under mild acid conditions in comparison to the other available reagents.

3

Aryl Chalcones as Efficient Precursors for Deriving Oxazine: Solvent-free Synthesis and Antimicrobial Activities of some Oxazine-2-amines

Thirunarayanan G., Sundararajan R., Arulkumaran R.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 4

82--97

EN

A series of some oxazine derivatives has been synthesised by fly-ash:H2SO4 catalyzed solvent-free cyclization of aryl chalcones and urea under microwave irradiation. The yields of the oxazines were more than 85 %. The synthesised oxazines were characterized by their physical constants, analytical and spectroscopic data. The antimicrobial activities of these oxazines have been studied using Bauer-Kirby method.