The mechanical hardness of the different phases of tantalum nitride (TaNx, x ≤ 1) thin films grown by the reactive planar dc magnetron sputtering technique at 300 °C have been evaluated. The different phases have been prepared by varying the nitrogen (N2) to argon (Ar) gas ratio R in the range 0.04–0.30. The phases present in each sample and their volume fractions are obtained from x-ray diffraction and Ta 4f7/2 binding energy x-ray photoelectron spectra, respectively. The grown TaN thin films are found to contain mainly cubic-TaN0.1, orthorhombic-Ta4N, orthorhombic-Ta6N2.5, hexagonal-TaN0.8 and cubic-TaN phases. The hardness corresponding to each phase has been derived from the experimental hardness values using ‘rule of mixtures’. A super hardness of ∼61.9 GPa is observed in orthorhombic Ta4N phase. With increase in R, a decrease in the surface oxidation of TaN has been observed. The reduced surface oxidation is attributed to the formation of stoichiometric TaN thin films. The surface morphology is found to change considerably with increase in R.
Machining parameters such as speed (v), feed (f) and depth of cut (d) play an
important role in determining the residual stress as well as the surface roughness of a
material. The material used for the present study is a nickel based super alloy Udiment 720
which finds applications in the manufacture of gas turbine engine components. Residual
stress and surface roughness measured on this material showed different magnitudes for
different combinations of milling parameters but did not reveal any definite trend. Analytical
relationships developed between the magnitudes of residual stress, surface roughness and
milling parameters indicated that combined effects of the milling parameters influence both
residual stress and surface roughness.
Effects of deposition parameters on residual stresses, hardness and electrical resistivity of nanoscale twinned 330 stainless steel thin films J. Appl. Phys. 97, 094302 (2005); 10.1063/1.1883724Reactive magnetron sputtering of CN x films: Ion bombardment effects and process characterization using optical emission spectroscopy Arcing is a common phenomenon in the sputtering process. Arcs and glow discharges emit electrons which may influence the physical properties of films. This article reports the properties of tantalum ͑Ta͒ thin films prepared by continuous dc magnetron sputtering in normal and arc-suppression modes. The substrate temperature was varied in the range of 300-673 K. The tantalum films were ϳ1.8 m thick and have good adherence to 316 stainless steel and single-crystal silicon substrates. The phase of the Ta thin film determines the electrical and tribological properties. The films deposited at 300 K using both methods were crystallized in a tetragonal structure ͑ phase͒ with a smooth surface ͑grain size of ϳ10 nm͒ and exhibited an electrical resistivity of ϳ194 ⍀ cm and a hardness of ϳ20 GPa. When the substrate temperature was 473 K and higher, the arc-suppression mode appears to influence the films to crystallize in the ␣ phase with a grain size of ϳ40 nm, whereas the normal power mode gave mixed phases  and ␣ beyond 473 K, the arc-suppression mode yields larger grain sizes in the Ta thin films and the hardness decreases. These changes in the physical properties in arc-suppression mode are attributed to either the change in plasma characteristics or the energetic particle bombardment onto the substrate, or both.
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