A novel Mo-W interlayer approach for CVD diamond deposition on steel

Abstract

Steel is the most widely used material in engineering for its cost/performance ratio and coatings are routinely applied on its surface to further improve its properties. Diamond coated steel parts are an option for many demanding industrial applications through prolonging the lifetime of steel parts, enhancement of tool performance as well as the reduction of wear rates. Direct deposition of diamond on steel using conventional chemical vapour deposition (CVD) processes is known to give poor results due to the preferential formation of amorphous carbon on iron, nickel and other elements as well as stresses induced from the significant difference in the thermal expansion coefficients of those materials. This article reports a novel approach of deposition of nanocrystalline diamond coatings on high-speed steel (M42) substrates using a multi-structured molybdenum (Mo) – tungsten (W) interlayer to form steel/Mo/Mo-W/W/diamond sandwich structures which overcome the adhesion problem related to direct magnetron sputtering deposition of pure tungsten. Surface, interface and tribology properties were evaluated to understand the role of such an interlayer structure. The multi-structured Mo-W interlayer has been proven to improve the adhesion between diamond films and steel substrates by acting as an effective diffusion barrier during the CVD diamond deposition.

Diamond Deposition on Iron and Steel Substrates: A Review

“…Each layer has a specific function: Ni could increase the Cu adhesion to steel substrate, a thick Cu layer accommodated the shear stresses induced by the films/substrate thermal expansion coefficient mismatch, while Ti promoted the CVD diamond nucleation and chemical bonding. A multi-structured Mo-W interlayer was experimented with by Kundrat et al, which could improve the adhesion between diamond films and steel substrates by acting as an effective diffusion barrier during the CVD diamond deposition [28,29].…”

Early stages of diamond growth on substrates with different carbon diffusivity

“…However, for 1 hour of deposition a continuous deposit with ballas-like morphology was found even on Fe and no delamination occurred after substrate cooling. This observation is significant for the specific case of iron, since Fe-based materials are extensively considered non-ideal substrates for direct coating of diamond without the deposition of an appropriate interfacial layer with the aim of increasing diamond adhesion and preventing its peeling off after cooling; Fe has indeed a catalytic behaviour with respect to sp 2 formation, and this is worsened by the high diffusivity that carbon has in this material, leading the formation of cluster of critical size for diamond nucleation difficult and long-time [39][40][41][42][43]. In the literature some positive results have been conversely reported on stainless steel, where problems in diamond growth on ferrous materials such as the surface graphitization, long incubation time, substrate softening and poor adhesion were overcome without the need of interfacial layer but with a low temperature deposition process [44].…”

Low-stress diamond films deposited on stainless steel by a two-step dropped power process in chemical vapor deposition

“…Diamond is a kind of carbon material which has lots of outstanding chemical and physical properties, such as excellent corrosion resistance, extremely high thermal conductivity, biocompatibility, etc [1][2][3]. Stainless steel is a kind of important metal materials, which is widely used in food industry, medical apparatus and so on.…”