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Academics and industry have sought after combining the exceptional properties of diamonds with the toughness of steel. Since the early 1990s several partial solutions have been found but chemical vapor deposition (CVD) diamond deposition on steel substrate continues to be a persistent problem. The main drawbacks are the high carbon diffusion from gas phase into substrate, the transition metals on the material surface that catalyze sp 2 bond formation, instead of sp 3 bonds, and the high thermal expansion coefficient (TEC) mismatch between diamond and steels. An intermediate layer has been found necessary to increase diamond adhesion. Literature has proposed many efficient intermediate layers as a diffusion barrier for both, carbon and iron, but most intermediate layers shown have not solved TEC mismatch. In this review, we briefly discuss the solutions that exclusively work as diffusion barrier and discuss in a broader way the ones that also solve, or may potentially solve, the TEC mismatch problem. We examine some multilayers, the iron borides, the chromium carbides, and vanadium carbides. We go through the most relevant results of the last two and a half decades, including recent advances in our group. Vanadium carbide looks promising since it has shown excellent diffusion barrier properties, its TEC is intermediary between diamond and steel and, it has been thickened to manage thermal stress relief. We also review a new deposition technique to set up intermediate layers: laser cladding. It is promising because of its versatility in mixing different materials and fusing and/or sintering them on a steel surface. We conclude by remarking on new perspectives.

The objective of this work is the Hot Filament Chemical Vapor Deposition (HFCVD) of diamond films on stainless steel substrates using a new technique for intermediate barrier forming, made by laser cladding process. In this technique, a powder layer is irradiated by a laser beam to melt the powder layer and the substrate surface layer to create the interlayer. The control of the laser beam parameters allows creating homogeneous coating layers, in rather large area in few seconds. In this work, the silicon carbide powder (SiC) was used to create an intermediate layer. Before the diamond growth, the samples were subjected to the seeding process with diamond powder. The diamond deposition was performed using Hot-Filament CVD reactor and the characterizations were Scanning Electron Microscopy, X-ray diffraction, Raman Scattering Spectroscopy and Scratch Test.

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Silicon Nitride is largely used as the base material to manufacture cutting tools. Due to its low thermal expansion coefficient it is ideal candidate for CVD diamond deposition. In this work, we functionalized the surface of silicon nitride inserts (Si3N4) with a polymer (PDDA Poly (diallyldimethylamonium chloride - Mw 40000)) to promote seeding with nanodiamond particles. The seeding was performed in water slurry containing 4 nm diamond particles dispersed by PSS Poly (sodium4-styrenesulfonate) polymer. CVD diamond films, with high nucleation density, were deposited in a hot filament reactor. Film morphology was characterized by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Diamond film quality was determined by Raman Spectroscopy. CVD diamond film adherence was evaluated using Rockwell C indentation.