Deposition of diamond-like carbon coatings: Conventional to non-conventional approaches for emerging markets

Diamond-like carbon (DLC) coatings are recognized for a broad range of industrial applications due to their superior mechanical properties such as high hardness, low friction, and promising wear resistance. DLC coatings are commonly produced with physical vapour deposition (PVD) and plasma-enhanced chemical vapour deposition (PECVD) methods. New DLC markets are emerging in electronics, biomedical, additive manufacturing and textiles sectors with industrial transformations. The conventional PVD and PECVD methods may have limited usage for depositing emerging DLC products due to their elevated thermal and high vacuum environment, lack of localized deposition function, and production throughput restrictions. This review begins by briefly describing DLC coatings background, the volume of research outcomes and the global revenue in the past decade and projections for the future. DLC structural designs made with conventional deposition methods and corresponding operational parameters are then discussed in detail and enhancement in conventional methods to improve DLC coating quality and to resolve unaddressed problems are summarized. The emerging DLC applications and potential of non-conventional methods to produce DLC coatings are critically analysed with specific attention to scientific, technological and economical aspects. Representative investigations suggest that DLC coatings can be produced with hardness values up to ~20 GPa using dielectric-barrier-discharge deposition, hydrophobicity up to ~167° with electrospray assisted plasma jet coating, high deposition rates up to ~6 μm/min with microwave resonator deposition, and critical load of ~30 N with a friction coefficient of ~0.1 when deposited with the plasma gun technique. The review concludes by recommending systematic investigations to optimize geometric and operational parameters of non-conventional DLC deposition methods which can produce high-quality DLC coatings at low temperatures and atmospheric pressures with scalability to meet emerging market demands.