Self-Lubricating Effect of FeWO4 Tribologically Synthesized from WC-(Fe-Mn-C) Composite during High-Speed Sliding against a HSS Disk

Abstract

WC-(Fe-Mn-C) composites with γ-iron and γ + α’ matrices were sintered and then tested at sliding speeds in the range 7–37 m/s. The coefficient of friction was exponentially reduced as a function of sliding speed reaching its minimum at 37 m/s. This behavior was provided by the mechanochemical formation of iron tungstate FeWO4 on the worn surfaces of composite samples. The lubricating effect of iron tungstate did not, however, allow for a reduction in wear. The worn surface was represented by a 3–10 μm-thickness tribological layer composed of fine WC and iron particles cemented by FeWO4. This layer provided the self-lubricating effect in high-speed (high-temperature) sliding because of its easy shear and quasi-viscous behavior. The underlying 25–65 μm of thickness layer was composed of only heat-affected WC and recrystallized iron grains.

Self-Lubricating Effect of WC/Y–TZP–Al2O3 Hybrid Ceramic–Matrix Composites with Dispersed Hadfield Steel Particles during High-Speed Sliding against an HSS Disk

“…In our case, there is another factor facilitating the agglomeration because sinter-forging was carried out at 1350 °C , i.e., above the 1143 °C that is the WC-Fe eutectic point [37]. Therefore, some liquid phase sintering might have occurred when Hadfield steel preferentially interacted with the WC grains, and possibly partially infiltrated into the already formed WC grain agglomerates due to its better wettability of the WC [7,10,47] as compared to that of ZrO2 [48] or Al2O3 [49], i.e., of Y-TZP-Al2O3 components, which formed their own agglomerates outside of the regions occupied by WC-Hadfield steel cermet. From the viewpoint of its chemical composition, the TrZ looks like a transition from undeformed as-sintered base material to the TL.…”

“…High-speed (high-temperature) sliding is gaining more and more interest in tribology in connection with studying tribological characteristics and behavior of new composite materials, especially if prospecting for those capable of demonstrating adaptation mechanisms [1][2][3][4][5][6][7][8][9]. These adaptation mechanisms are usually related to the generation of anti-friction or/and anti-wear films on the worn surfaces from the components of materials used in the tribological testing as well as active environmental elements such as oxygen [1][2][3][4][5][6][7][8][9].…”

“…High-speed (high-temperature) sliding is gaining more and more interest in tribology in connection with studying tribological characteristics and behavior of new composite materials, especially if prospecting for those capable of demonstrating adaptation mechanisms [1][2][3][4][5][6][7][8][9]. These adaptation mechanisms are usually related to the generation of anti-friction or/and anti-wear films on the worn surfaces from the components of materials used in the tribological testing as well as active environmental elements such as oxygen [1][2][3][4][5][6][7][8][9]. The first stage of such an adaptation mechanism can be intense deformation or grain refining, generation of wear debris, adhesive transfer, and high-temperature tribo-oxidation of them with the mechanochemical formation of low-friction and self-lubricating products such as solid or liquid mixed oxides, etc.…”

“…The first stage of such an adaptation mechanism can be intense deformation or grain refining, generation of wear debris, adhesive transfer, and high-temperature tribo-oxidation of them with the mechanochemical formation of low-friction and self-lubricating products such as solid or liquid mixed oxides, etc. [1][2][3][4][5][6][7][8][9].…”

“…High-speed sliding usually means unlubricated sliding at speeds in the range of 5-90 m/s and only a limited number of materials can be capable of sustaining that harsh condition [7][8][9][10][11][12][13][14][15][16][17][18][19]. Those may be hybrid sliding pairs with ceramics, ceramic matrix (CMCs), or metallic matrix (MMCs) composites rubbed against hardened alloyed steel counterbodies [7][8][9][10][11][12][13][14][15][16][17][18][19]. It is worthwhile noting that despite temperatures as high as 1500-3000 • C that the melted Hadfield steel.…”