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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 (TiB 2) prepared by PVD (Physical Vapour Deposition) sputtering onto H-13 substrates are studied as potential wear-resistant coatings for forging die applications. The TiB 2 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 TiB 2 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% TiB 2 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 TiB 2 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/TiB 2 multilayer coatings are approximately three times lower than those measured on the substrate, thus validating the increased wear resistance offered by these composite coatings.

Shape Memory Alloys (SMAs) coatings of NiTi and NiTiHf have been deposited onto Si substrates using pulse DC sputtering. Coatings of NiTi with compositions containing 45 to 65 at% Ti have been fabricated by co-sputtering NiTi with Ti. NiTiHf coatings with Hf compositions ranging from 2 to 30 at% Hf have been fabricated by co-sputtering NiTi with Hf. XRD results reveal the as-deposited coatings are amorphous. A high temperature, 1100 o C anneal followed by a low temperature, 550 o C anneal was employed to crystallise the coatings. The XRD then shows the coatings to be martensitic at room temperature. Two sets of samples were produced for characterisation; one set was used for indentation studies and the other set used to prepare freestanding films required for differential scanning calorimetry, (DSC) studies. Using the DSC, a NiTi coating containing 52 at% Ti shows an endothermic austenite peak phase transformation, (A p) at around 105 o C and an exothermic peak martensite phase transformation, (M p) at 65 o C, resulting in a hysteresis of 40 o C. For a NiTi coating containing 65 at% Ti the hysteresis remained unchanged at 40 o C, but there was a decrease in the phase transformation enthalpies when compared with the coatings containing 52 at% Ti. Calculated phase transformation enthalpies in the NiTi coatings ranged from 6 to 13 J/g for the austenite phase and-8 to-11 J/g for the martensite phase.