Abstract
Oxygen vacancies in WO2.9 yield to formation of easy shear planes and they can potentially be applied in boundary lubrication conditions for reducing friction. Mechanical and tribological properties of pulsed electric current sintered monolithic WO2.9 were studied by nanoindentation and nanoscratch, and the composites of ZrO2 + WO2.9 with reciprocating wear tests. Hardness of WO2.9 at 25 °C was ~11 GPa and reduced elastic modulus was ~150 GPa. The ploughing dominated coefficient of friction as between 0.09 and 0.24 when measured against a Berkovich diamond tip. The composite n-ZrO2 + 10 vol% WO2.9 presented the lowest CoF, and wear rate 10−10 mm3/Nm measured under 10 N load against alumina ball (6 mm diameter) due to WO2.9 acting as a solid lubricant.
Highlights
The most common counter measure against wear and reducing friction in dry friction conditions is protecting surfaces of moving parts by hard coatings
The present study focuses first on the mechanical and friction properties of oxygen deficient tungsten oxide phase W20O58 (WO2.9) and seeks answer to the question if it is possible to utilize this phase in a ceramic matrix composite as a solid lubricant at room temperature
Based on the results presented the following conclusions can be made: I) Magneli phase oxide W20O58 was studied as a solid lubricant within a ceramic matrix
Summary
The most common counter measure against wear and reducing friction in dry friction conditions is protecting surfaces of moving parts by hard coatings. In either case, reducing friction of contacts by self-lubrication without surface modification can be beneficial This is even more distinct under boundary lubrication conditions where surfaces are in contact at asperity couples and wear and friction are determined by the interaction between the solid bodies that are in contact [7]. This interaction typi cally yields heat generation due to friction and is detrimental on the wear mechanism [6]. In presence of a metal constituent, the increase in surface temperature leads to the formation of an oxide layer This may either reduce the coefficient of friction (CoF), or increase it due to phase transformations and reactions occurring at counter materials’ surfaces [6]. Under static or dynamic loading conditions the surface oxide may deteriorate the mechanical properties of the material quickly
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