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

Abstract

WC/Y–TZP–Al2O3 hybrid ceramic–matrix composites (CMCs) with dispersed Hadfield steel particles were sintered and then tested at sliding speeds in the range of 7–37 m/s and contact pressure 5 MPa. Fast and low-temperature sinter-forging allowed obtaining micron-sized WC grains, submicron-sized alumina-reinforced yttria partially stabilized polycrystalline tetragonal zirconia (Y–TZP–Al2O3), and evenly distributed Hadfield steel grains. Such a microstructure provided new hybrid characteristics combining high hardness with high fracture toughness and tribological adaptation. The CMCs demonstrated low friction and high wear resistance that were better than those demonstrated by other composite materials such as, for example, MAX-phase composites, zirconia-base ceramics, ZrB2-SiC ceramics, and metal matrix WC–(Fe–Mn–C) composites. These good tribological characteristics were obtained due to the in situ mechanochemical formation of iron tungstates FeWO4 and Fe2WO6 on the worn surfaces of composite samples. These mixed oxides were included in multilayer subsurface structures that provided the self-lubricating and self-healing effects in high-speed sliding because of their easy shear and quasi-viscous behavior.

In-Situ Al-Mg Alloy Base Composite Reinforced by Oxides and Intermetallic Compounds Resulted from Decomposition of ZrW2O8 during Multipass Friction Stir Processing

“…Tribological adaptation mechanisms show the effect of tribo-oxidation of W and Fe contained in either one or both counterbody materials with in-situ formation of lubricative FeWO 4 and Fe 2 WO 6 mixed oxides [ 37 , 38 , 39 ]. For example, it was established that some quasi-viscous subsurface multilayer structures have been formed on the WC/Y–TZP–Al 2 O 3 /Hadfield steel composites rubbed against an HSS counterbody at high sliding speeds.…”

“…For example, it was established that some quasi-viscous subsurface multilayer structures have been formed on the WC/Y–TZP–Al 2 O 3 /Hadfield steel composites rubbed against an HSS counterbody at high sliding speeds. These structures consisted of FeWO 4 and Fe 2 WO 6 which encapsulated wear debris and carbide fragments thus forming microcomposite mechanically mixed layers capable of healing the voids and cracks as well as simultaneously reducing wear and friction [ 38 ].…”

Evidence of Tribological Adaptation Controlled by Tribosynthesis of FeWO4 on an WC-Reinforced Electron Beam M2 Steel Coating Rubbed against a HSS Disk in a Range of Sliding Speeds

“…The study of tribological adaptation mechanisms in new composite materials is necessary for their successful application in various industries [1][2][3][4][5][6][7]. There is a well-known, but insufficiently studied, tribological adaptation mechanism for materials containing elements such as W and Fe that is related to the formation of a tribochemically synthesized FeWO 4 mixed oxide on a worn surface, which can serve as a solid lubricant due to the presence of crystallographic easy slip planes [8][9][10][11][12]. The tribosynthesis of iron tungstates was found during sliding on a WC-(Fe-Mn-C) composites [10] and then was used for developing a wear-resistant hybrid WC/Y-TZP-Al 2 O 3 composite with dispersed Hadfield steel particles [9].…”

“…There is a well-known, but insufficiently studied, tribological adaptation mechanism for materials containing elements such as W and Fe that is related to the formation of a tribochemically synthesized FeWO 4 mixed oxide on a worn surface, which can serve as a solid lubricant due to the presence of crystallographic easy slip planes [8][9][10][11][12]. The tribosynthesis of iron tungstates was found during sliding on a WC-(Fe-Mn-C) composites [10] and then was used for developing a wear-resistant hybrid WC/Y-TZP-Al 2 O 3 composite with dispersed Hadfield steel particles [9]. Another example of tribological adaptation is tribosynthesis of a copper tungstate CuWO 4 on the worn surface of W-31 wt.% Cu magnetic pulse consolidated samples at 400-450 • C that also allowed reducing friction [13].…”

“…An elemental composition of the MMCs is an important issue in view of tribological adaptation when in-situ forming mixed oxides may not simply mitigate the adhesive interaction between the surfaces but considerably improve the lubrication especially at elevated temperatures. Tungsten is an element that is capable of forming not only hard, wear-resistant carbides but also the FeWO 4 and Fe 2 WO 6 oxides characterized by reduced friction, especially at high temperature sliding [9]. However, there is still lack of reliable data of formation of these oxides in sliding the W/Fe containing materials.…”