Machine-tool life is one limiting factor affecting productivity. The requirement for wear-resistant materials for cutting tools to increase their longevity is therefore critical. Titanium diboride (TiB₂) coated cutting tools have been successfully employed for machining of AlSi alloys widely used in the automotive industry. This paper presents a methodological approach to improving the self-lubricating properties within the cutting zone of a tungsten carbide milling insert precoated with TiB₂, thereby increasing the operational life of the tool. A unique hybrid Physical Vapor Deposition (PVD) system was used in this study, allowing diamond-like carbon (DLC) to be deposited by filtered cathodic vacuum arc (FCVA) while PVD magnetron sputtering was employed to deposit WS₂. A series of ~100-nm monolayer DLC coatings were prepared at a negative bias voltage ranging between −50 and −200 V, along with multilayered DLC-WS₂ coatings (total thickness ~500 nm) with varying number of layers (two to 24 in total). The wear rate of the coated milling inserts was investigated by measuring the flank wear during face milling of an Al-10Si. It was ascertained that employing monolayer DLC coating reduced the coated tool wear rate by ~85% compared to a TiB₂ benchmark. Combining DLC with WS₂ as a multilayered coating further improved tool life. The best tribological properties were found for a two-layer DLC-WS₂ coating which decreased wear rate by ~75% compared to TiB₂, with a measured coefficient of friction of 0.05.

The lifetimes and the premature wear of machining tools impact on manufacturing efficiencies and productivities. A significant proportion of machining tool damage can be attributed to component wear. Here, titanium aluminium nitride (TiAlN) multi-layered with titanium diboride (TiB₂) prepared by PVD (Physical Vapour Deposition) sputtering onto H-13 substrates are studied as potential wear-resistant coatings for forging die applications. The TiB₂ content has been altered and two-sets of coating systems with a bilayer thickness either less than or greater than 1 μm are investigated by tribological and microstructural analysis. XRD analysis of the multilayers reveals the coatings to be predominately dominated by the TiAlN (200) peak, with additional peaks of TiN (200) and Ti (101) at a TiB₂ content of 9%. Progressive loads increasing to 100 N enabled the friction coefficients and the coating failure at a critical load to be determined. Friction coefficients of around 0.2 have been measured in a coating containing 9% TiB₂ at critical loads of approximately 70 N. Bi-directional wear tests reveal that bilayers with thicknesses greater than 1 μm have frictional coefficients that are approximately 50% lower than those where the bilayer is less than 1 μm. This is due to the greater ability of thicker bilayers to uniformly distribute the stress within the layers. There are two observed frictional coefficient regimes corresponding to a lower and higher rate of material loss. At the lower regime, with TiB₂ contents below 20%, material loss occurs mainly via delamination between the layers, whilst at compositions above this, material loss occurs via a break-up of material into finer particles that in combination with the higher loads results in greater material loss. The measured wear scar volumes for the TiAlN/TiB₂ multilayer coatings are approximately three times lower than those measured on the substrate, thus validating the increased wear resistance offered by these composite coatings.