High-temperature properties of nanocomposite TiBxNy and TiBxCy coatings

High-temperature investigations on nanocomposite TiBxNy and TiBxCy coatings were performed to determine their thermal stability. All coatings investig ated were prepared by means of unbalanced DC magnetron co-sputtering using either a segmented TiN/TiB2 or TiC/TiB2 target. Recovery and recrystallizat ion behavior were characterized by means of stress measurements during ther mal annealing and differential scanning calorimetry (DSC). The nanocomposit e coatings used for DSC measurements were studied by X-ray diffraction (XRD ) and scanning electron microscopy (SEM). XRD of these coatings showed a pr onounced growth of the individual phases after the DSC measurements. Theref ore, the total enthalpy change during DSC can be attributed to grain growth of the nanocrystalline phases. The grain sizes after the DSC treatment as analyzed by XRD and SEM are in excellent agreement with the grain sizes cal culated from the exothermic peaks of the DSC measurements. Grain growth occ urred for the individual phases in TiB1.2N0.5 and TiB1.2C0.6 coatings durin g heating up to 1400 degreesC from approximately 4 to 15 nm and 4 to 5 nm, respectively. Recovery effects of the coatings investigated are strongly in fluenced by the ion bombardment during film growth as well as by the chemic al composition of the coatings. (C) 2000 Published by Elsevier Science B.V. All rights reserved.