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Stanishevsky A.V.,University of Alabama at Birmingham | Walock M.J.,University of Alabama at Birmingham | Walock M.J.,Arts et Metiers ParisTech | Zou Y.,University of Alabama at Birmingham | And 4 more authors.

Tungsten carbide-based coatings have been used in a wide variety of industrial applications such as high speed cutting tools, extrusion dies, drills, aerospace industries, and more. A few reports on ternary and quaternary coatings of WC with other elements indicate good prospects for these material systems. The present study focuses on the formation of quaternary WC-Cr-N and WC-Al-N coatings during the simultaneous reactive RF-magnetron sputtering of tungsten carbide and Al or Cr targets in an argon/nitrogen gas mixture. The resulting coatings, with thicknesses of 3.5 μm-8.2 μm, were characterized by using several analytical techniques including X-ray diffraction, SEM/EDS, AFM, and X-ray photoelectron spectroscopy. WC-Cr-N and WC-Al-N coatings with high levels of tungsten (i.e. more than 50 at.% of the total metal content) demonstrated dense microstructure. Coatings with lower tungsten content formed columnar grain microstructure, with different surface morphologies depending on the process parameters. It was proposed that crystalline tungsten carbide (with partial N-substitution of C atoms) and chromium (or aluminum) nitride phases coexist in the coatings when the amount of tungsten was greater than 50 at.% of the total metal content; while at lower tungsten content, the dominating crystalline phase is either W-doped CrN1-y or AlN1-y solid solution, with WC1-x and small amounts of free sp2-bonded carbon present as X-ray amorphous phases. © 2012 Elsevier Ltd. All rights reserved. Source

Jouini N.,Laboratoire Of Mecanique Materiaux Et Procedes | Revel P.,CNRS Roberval Laboratory (Mechanical Research Unit) | Mazeran P.-E.,CNRS Roberval Laboratory (Mechanical Research Unit) | Bigerelle M.,University of Valenciennes and HainautCambresis
Tribology International

In this paper, precision hard turning is proposed for the finishing of the AISI 52100 bearing components to improve rolling contact fatigue life. This finishing process induces a homogenous microstructure at surface and subsurface layers. Fatigue life tests performed on a twin-disk machine show that rolling contact fatigue life increases as Ra value decreases. The bearing components reached 0.32 million cycles for Ra=0.25 μm and 5.2 million cycles for Ra=0.11 μm. In comparison, the bearing components achieved 1.2 million cycles with grinding (Ra=0.2 μm) and 3.2 million cycles with grinding followed by honing (Ra=0.05 μm) respectively. © 2012 Elsevier Ltd. Source

Khaldi C.,Laboratoire Of Mecanique Materiaux Et Procedes | Boussami S.,Laboratoire Of Mecanique Materiaux Et Procedes | Rejeb B.B.,Laboratoire Of Mecanique Materiaux Et Procedes | Mathlouthi H.,Laboratoire Of Mecanique Materiaux Et Procedes | Lamloumi J.,Laboratoire Of Mecanique Materiaux Et Procedes
Materials Science and Engineering B: Solid-State Materials for Advanced Technology

The thermodynamic parameters, electrochemical capacity, equilibrium potential and the equilibrium pressure, of LaNi3.55Mn 0.4Al0.3Co0.75 and LaNi3.55Mn 0.4Al0.3Fe0.75 alloys have been evaluated from the electrochemical isotherms (C/30 and OCV methods) and CV technique. A comparative study has been done between the parameter values deduced from the electrochemical methods and the solid-gas method. The parameter values deduced from the electrochemical methods are influenced by the electrochemical corrosion of the alloys in aqueous KOH electrolyte. The corrosion behaviour of the LaNi3.55Mn0.4Al0.3Co0.75 and LaNi3.55Mn0.4Al0.3Fe0.75 electrodes after activation was investigated using the method of the potentiodynamic polarization. The variation of current and potential corrosion values with the state of charge (SOC) show that the substitution of cobalt by iron accentuates the corrosion process. The high-rate dischargeability (HRD) of the LaNi 3.55Mn0.4Al0.3Co0.75 and LaNi 3.55Mn0.4Al0.3Fe0.75 alloys was examined. By increasing the discharge current the (HRD) decrease linearly for both the alloys and for the LaNi3.55Mn0.4Al 0.3Fe0.75 compound is greater then for the LaNi 3.55Mn0.4Al0.3Co0.75 one. © 2010 Elsevier B.V. All rights reserved. Source

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