Unveiling the wear behavior of multi-component ultra-high temperature ceramic thin coatings with pulsed electro-spark deposition

The study presents a novel approach using pulsed electro-spark deposition (PED) to apply a thin protective coating of multi-component ultra-high temperature ceramics (MC-UHTCs) on a steel substrate. A single solidsolution phase of (TaNbHfTi)C-based MC-UHTC electrode is prepared using spark plasma sintering (SPS). The coating process involves melting, rapid re-solidification, and forming nano-grains (15-20 nm) resembling splashlike features. MC-UHTC coating remains stable without oxidation and any phase transformation. The bonding between the coating and the substrate is strong, regardless of the coating thickness, which can vary from <1 mu m to over 25 mu m. Scratch testing along the interface demonstrates that the MC-UHTC coating exhibits improved wear resistance compared to the uncoated steel substrate. This improvement is attributed to the significantly higher hardness of the coating, which is up to 4.5 times greater than substrate. The dominant wear mechanisms observed include plowing in the substrate, micro-cracking at the interface, lateral cracking and brittle fracture in the MC-UHTC coating. Overall, this study presents promising opportunities for developing innovative protective MC-UHTC coatings without needing expensive environmental chambers while preserving their chemical functionality. By employing the PED technique and utilizing MC-UHTCs, the wear resistance of structural metallic components can be enhanced effectively.