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Research Papers: Coatings & Solid Lubricants

Self Lubricating Composite Coatings Containing TiC–MnS or WC-MnS Compounds Prepared by the Plasma Transferred Arc (PTA) Technique

[+] Author and Article Information
P. Skarvelis, G. D. Papadimitriou

Department of Metallurgy and Materials Technology, School of Mining and Metallurgical Engineering, National Technical University of Athens, 9 Iroon Polytechniou Str., 15780 Athens, Greece

M. Perraki

Department of Geosciences, School of Mining and Metallurgical Engineering, National Technical University of Athens, 9 Iroon Polytechniou Str., 15780 Athens, Greece

J. Tribol 132(3), 031302 (Jun 16, 2010) (8 pages) doi:10.1115/1.4001649 History: Received November 02, 2009; Revised April 19, 2010; Published June 16, 2010; Online June 16, 2010

Composite coatings containing manganese sulphide as lubricating addition and enhanced with hard carbide particles (TiC, WC) were synthesized on a plain steel substrate using the plasma transferred arc technique. The coatings are well bonded to the substrate, have a thickness of about 1 mm, and are free of any visual defects. They consist mainly of a martensitic or ferritic matrix enhanced with titanium or tungsten carbides and a dispersion of MnS particles. The tribological properties of the composites are assessed using a pin-on-disk device. Both composites possess self lubricating properties, due to the formation of a thin layer of manganese sulphide on their wear tracks. The corresponding friction coefficients vary between 0.25 and 0.28, compared with 0.50–0.60 obtained from similar hard coatings without MnS addition. The wear rates are of the order of 105mm3/mN and are two orders of magnitude lower than those obtained from the substrate material with MnS addition, but without the presence of hard enhancing particles. The wear regime is mild abrasion due to the combined action of both lubricating (MnS) and hard (TiC or WC) particles.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Typical micrographs of series A (TiC/MnS) coatings: (a) cross section and (b) microstructure

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Figure 2

(a) BEI of the microstructure of series A coatings. The matrix is martensitic. Dark gray particles belong to TiC. MnS is present both as small individual (black) particles and as black layers on the surface of TiC particles. (b, c, d) EDS analyses on (b) MnS, (c) TiC particles, and (c) the martensitic matrix.

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Figure 3

X-ray diffraction spectrum of series A coating. The inserted XRD spectrum was performed between 2θ=47–57 deg, in order to show more clearly the presence of Ti2S.

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Figure 4

(a) Interface and (b) typical microstructure of series B coatings (BEI)

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Figure 5

X-ray diffraction spectrum for series B coatings

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Figure 6

Fe-rich corner of the Fe-W-C ternary diagram (19)

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Figure 7

(a) BEI of series B coatings, showing the microconstituents marked by arrows. (b, c, d) EDS analyses on (b) MnS, (c) WC particles, and (d) on the ferritic matrix.

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Figure 8

Friction coefficient for the experimental range of applied load and velocity examined, for both series A (TiC/MnS) and series B (WC/MnS) coatings

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Figure 9

(a) Secondary electron image (SEI) of the wear track at 19.6 N applied load and 0.9 m/s sliding velocity, (b) BEI of corresponding alumina pin scar, and (c) EDS diagram of the alumina pin scar

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Figure 10

(a) BEI of a globular inclusion of MnS in AISI 1522H steel, (b) corresponding EDS diagram of the inclusion, and (c) comparison of reference Raman spectra of the MnS inclusion and of different places on the wear track

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Figure 11

Wear rate for the experimental range of applied load and velocity examined, for both series A (TiC/MnS) and series B (WC/MnS) coatings

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Figure 12

Friction coefficient versus sliding distance, for the applied load of 19.6 N and sliding velocities of 0.3 m/s, 0.6 m/s, and 0.9 m/s

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Figure 13

Wear track of series B coatings for 19.6 N applied load and 0.6 m/s sliding velocity

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