June/July 2013

Canadian Metallurgical Quarterly

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Excerpts taken from abstracts in CMQ, Vol. 50, No. 2.
To subscribe – www.cmq-online.ca

Assessment of slag and copper equilibrium in a vaniukov two-zone converter

Oxide nickel ores smelting of ferronickel in two-zone vaniukov furnace

Heterogeneous electrospark deposition of nicocraly

Effect of electrolyte additives on microstructure and properties of electroplated chromium coatings

Solvent refining of silicon using nickel as impurity getter

Influence of cooling rate and composition on the formation of intermetallic phases in solidifying al–fe–si melts

Investigation of corrosion-enhanced erosion of carbon steel in slurries using nano-indentation

Kinetics of mild steel corrosion in aqueous formic acid solutions

Ti/TiO2/Ni2+ interface: unexpected protection of Ti by Ni2+ cations in hot sulphuric acid


Assessment of slag and copper equilibrium in a vaniukov two-zone converter

L.B. Tsymbulov, JS Gipronickel Institute, 11 Grazhdansky Prospect, Saint-Petersburg, Russia

ABSTRACT A brand new process of blister copper production from copper matte and concentrates in the two-zone Vaniukov converter has been developed at the Gipronickel Institute facility. Thermodynamic analysis of exchange interaction has been performed for the “slag melt-metal phase formed in the over-the-lance area of the Vaniukov converter reduction zone” system and for “slag melt-bottom phase of blister copper located in the bottom (under-the-lance) area of the Vaniukov converter” system. Based on the thermodynamic analysis data, the original design of the two-zone Vaniukov converter has been proven to be able to create conditions ensuring production of blister copper of higher quality, as compared to the one-zone Vaniukov converter process, copper concentration in slag being substantially lower.

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Oxide nickel ores smelting of ferronickel in two-zone vaniukov furnace

L.B. Tsymbulov, M.V. Knyazev and L.Sh. Tsemekhman, JS Gipronickel Institute, 11 Grazhdansky Prospect, Saint-Petersburg, Russia

ABSTRACT Gipronickel Institute is developing a brand new process of Kempirsay Deposit’ nickel oxide ore treatment to ferronickel based on Vanuikov furnace smelting technology. Results of the extended laboratory scale tests using pilot Vanuikov two-zone furnace are presented. It is demonstrated that treatment of relatively poor nickel oxide ore (Ni – 1.05 mass %) according to the said technology can result in production of high grade ferronickel (Ni3≥20%) at high rate nickel recovery into ferronickel (>90%). Technological peculiarities of the processes taking place in the furnace’ smelting and reduction areas are considered.

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Heterogeneous electrospark deposition of nicocraly

G. Goodall, C. Kaplin and M. Brochu, McGill University, Mining and Materials Engineering Department, Montreal, Quebec, Canada

ABSTRACT GElectrospark deposition (ESD) is a micro-arc welding process that has been successfully used to deposit an autogenous ultrafine NiCoCrAlY coating. Primary solidification of the β phase shows epitaxial growth where orientation and heat flux coincide. ECCI imaging of the deposits show a homogeneous distribution of non-stochiometric phases from the rapid solidification of the ESD process. EBSD mapping of the deposit indicates an ultra fine β structure can grow epitaxially where favourable conditions prevail. The equiaxed structure associated with the γ to β solidification shift was not observed and is believed to result from the homogeneous electrode and substrate compositions. Oxidation of the deposit shows advantageous alumina growth stemming from the ultra fine aluminum rich phase. The transition from θ to α alumina was nearly complete in only 6 hours at 1000°C in air.

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Effect of electrolyte additives on microstructure and properties of electroplated chromium coatings

I. Makarov, Inotec Coatings and Hydraulics Inc, Edmonton, Alberta, Canada; J. Chen, Department of Chemical & Materials Engineering, University of Alberta, Edmonton, Alberta, Canada; E. Yurasovskaya, Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada; J. McCracken, Inotec Coatings and Hydraulics Inc, Edmonton, Alberta, Canada; and H. Henein, Department of Chemical & Materials Engineering, University of Alberta, Edmonton, Alberta, Canada

ABSTRACT Recent progress in environmental science provides an incentive to explore the use of hexavalent chromium for anti-corrosion and wear protection purposes. To this end, this work aims to explore the evolution of the microstructure of chromium coatings as a function of electric current through the electrolyte in the presence of organic and nonorganic additives. In this study, the fundamental properties of electroplating related to hard chromium such as hardness (wear resistance) and cathode efficiency are reviewed with respect to cathode current. The results obtained show that the microstructure is sensitive to the presence of organic admixtures in the plating solution. In addition, the effect of hard micro particles on the plating process at enhanced values of cathode current is reported. The cathode efficiency for different plating speeds and in different chromium electrolytes is calculated from the experimental results.

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Solvent refining of silicon using nickel as impurity getter

Z. Yin, A. Oliazadeh, S. Esfahani, M. Johnston and M. Barati, Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario, Canada

ABSTRACT The effectiveness of Ni as an impurity trapper in refining of silicon has been studied. Metallurgical grade silicon was alloyed with Ni and the molten alloy solidified by slow cooling at various cooling rates. Silicon dendrites grown during solidification of the alloy were subsequently recovered from the matrix by employing a heavy media separation technique. The process efficiency was studied in terms of the effectiveness of the physical separation technique and the degree of purification of Si.

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Influence of cooling rate and composition on the formation of intermetallic phases in solidifying al–fe–si melts

D. Panahi and D.V. Malakhov, Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada; and M. Gallerneault and P. Marois, Novelis Global Technology Centre, Kingston, Ontario, Canada

ABSTRACT Aluminum alloys containing 0.3% Fe and 0.05% Si, 0.3% Fe and 0.15% Si, 0.3% Fe and 0.45% Si, 0.5% Fe, and 0.2% Si were solidified with different cooling rates. Shapes of intermetallic particles and their spatial distribution in the alloys were characterized by optical and scanning electron microscopy. X-ray diffraction analysis was used to establish the types of intermetallic phases extracted from the alloys by dissolving the FCC matrix in boiling phenol. The influence of melt superheating on the microstructure was analyzed by comparing phase portraits of alloys solidified from melts whose temperatures prior to casting were 100°C and 350°C above the liquidus.

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Investigation of corrosion-enhanced erosion of carbon steel in slurries using nano-indentation

K. Wang, B.T. Lu and J.L. Luo, Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada

ABSTRACT When cathodic protection is applied, there is no impact of slurry chemistry on either the erosion behavior of carbon steel or the in situ surface hardness. Anodic dissolution of the steel surface reduces the surface hardness and promotes erosion. The corrosion-enhanced erosion behavior is slurry chemistry dependent. The erosion wastage in acidic slurries is much higher than that in neutral and alkaline ones. The slurry chemistry effect on corrosion-enhanced erosion behavior correlates well with surface hardness degradation as determined using nano-indentation technique. The increase in surface hardness degradation in acidic chemistry is greater than that in neutral and alkaline ones, in which there is similar surface hardness reduction. The results suggest that both corrosion current density and electrolyte chemistry affect the mechanical properties of surface layers, and that leads to corrosion-enhanced erosion.

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Kinetics of mild steel corrosion in aqueous formic acid solutions

S.K. Singh, Department of Applied Chemistry, Institute of Technology, Banaras Hindu University, Varanasi, India, and Department of Chemistry, University of Delhi, Delhi; and A.K. Mukherjee and M.M. Singh, Department of Applied Chemistry, Institute of Technology, Banaras Hindu University, Varanasi, India

ABSTRACT The kinetics of the corrosion of mild steel in formic acid solutions of different concentrations has been studied at 25, 35 and 45° C. The corrosion rate was evaluated by weight loss and electrochemical polarization techniques. There is good agreement between the data obtained by the two techniques. The maximum corrosion rate was observed in close vicinity of 20% formic acid solution. The anodic polarization curves show active corrosion behaviour of mild steel over the whole range of potential at each concentration and temperature. The shape of anodic and cathodic polarization curves was found to be almost independent of the temperature and the concentration of formic acid. However, the curves bodily shift towards lower or higher current density side with change in the concentration of the electrolyte. With rise in temperature, the shift of polarization curve regularly occurs towards higher current density side. The surface morphology of the specimens has been studied by scanning electron microscopy. The micrographs indicate uniform corrosion of mild steel in formic acid solution.

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Ti/TiO2/Ni2+ interface: unexpected protection of Ti by Ni2+ cations in hot sulphuric acid

O. Yépez and J. Shirokoff, Faculty of Engineering and Applied Sciences, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada

ABSTRACT The processing of nickel ores involves: high temperatures (>100ºC), high [H2SO4] and high [Cl-]. Despite the severity of this service pure titanium can be used because it presents very low corrosion rates. Looking for the fundamental causes of this behaviour, it was found that the potential of the couple Ti4+ /Ti3+ shifted to more negative potentials than the couple Ni2+/Ni in these conditions. Thus, Ni2+ was reduced to Ni metal oxidizing Ti3+ to Ti4+. This increased the concentration of Ti4+ which is critical for the formation of the protective TiO2 layer. In turn, the TiO2 passivates the active titanium dissolution. Also, the deposited Ni catalyzes the cathodic kinetics producing a mixed potential in the passive region for titanium. This process involves Ti/TiO2/Ni2+ and Ti/Ni2+ interface systems and Ti/Ni2+ behaviour is somewhat like a titanium-nickel alloy.

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