Microstructure and dry sliding wear evaluation of functionally graded coating deposited via atmospheric plasma spray

Surfaces are commonly enhanced with wear-resistant coatings to improve their resistance to abrasion, erosion, and other forms of wear. These coatings play a crucial role in extending the lifespan and improving the performance of materials and components exposed to challenging conditions. The objective of the current study is to deposit thermally sprayed 3-layer TiC-12Co-10ZrO₂/NiCoCrAlMo functionally graded coatings on SS410 substrates using atmospheric plasma spray. The results revealed that by employing appropriate ceramic proportions, the microhardness of graded coatings increased to 990.4 HV, which is approximately 3.21 times higher than that of the substrate. Furthermore, the tribological properties of graded coating exhibited superior resistance compared to the substrate, where process settings were varied. Specifically, graded coating samples subjected to the applied load, sliding distance, and sliding velocity showed improved wear resistance of 78.51%, 68.42%, and 76.66% respectively in extreme conditions compared with uncoated samples. The characterization of the worn surface revealed a sequential occurrence of wear mechanisms: abrasive, adhesive, and delamination. The formation of TiO₂ and Cr₂O₃ tribo-oxide film protects the surface against the wear mechanism and is applicable in extreme wear environments.