Process Investigation Of Immiscible Metallic Cu-Nb Nanocomposite Coatings Deposited By Deep Oscillation Magnetron Sputtering

Deep oscillation magnetron sputtering is a new variation of high power pulsed magnetron sputtering technology.Micro-pulse is one of the core rub to control deep oscillation magnetron sputtering.The deep oscillation magnetron sputtering was employed in this paper to deposit nano Nb coatings and immscible Cu-Nb nanocomposite coatings.Through adjusting the pulse on and off time of the micropulse conversion time,the discharge characteristics,the its infulence on coatings structure and mechanical properties were systematically studied.The micropulse duty cycle for the deposition of better nano Nb coatings and Cu-Nb nanocomposite coatings was selected.The pulse conversion time for depositing the Nb coatings and the Cu-Nb coatings were adjustetd seperately.τ_on increased from 6μs to 12μs and 8μs to 14μs orτ_off decreased from40μs to 10μs and 40μs to 15μs with peak current,peak voltage,peak power and average power showe same trend.When the Nb targetτ_on increased from 6μs to 12μs and the Cu-Nb target increased from 8μs to 14μs,P_a increased from 0.80 kW to 1.30 kW and 0.50 kW to1.40 kW.When the Nb targetτ_off decreased from 40μs to 10μs and the Cu-Nb target decreased from 40μs to 15μs,P_a increased from 0.70 kW to 1.80 kW and 0.50 kW to 1.10kW.The peak current,peak voltage,peak power,and average power of the deep oscillation magnetron sputtering could be adjusted through changing the pulse on and pulse off time of the micropulse time conversion.The fixed micro-pulse off time was 30μs,and the nano Nb mainly presented the（110）preferred orientation and had a pronounced columnar grain characteristic.The grain sizes of the Nb coatings were caculated by Debye Scherrer method,which were from 7.5 nm to 10.0nm,and finally to 8.10 nm,and roughness of the coatings changed from 0.03μm to 0.07μm.All coatings showed residual compressive stress.When the pulse on time was 8μs,the grain sizes of the coatings reached the minimum of 5.9 nm,with the highest hardness of 15 GPa.Cu-Nb nanocomposite coatings showed relative FWHM of diffusive at Nb（110）and the distribution of Cu-Nb elements in the coatings was uniform without obvious segregation.Through increasing the pulse on time,the composition of Nb in the coatings increased from65.82%to 70.54%,with the surface roughness of coatings from 0.03μm to 0.08μm.When the micropulse on time was 14μs,the highest hardness achieved 16 GPa,with the residual compressive stress of 1.79 GPa.The micro-pulse on time was fixed at 8μs,the Nb coatings showed（110）preferred orientation with a pronounced columnar characteristic,the grain sizes of coatings decreased from 12.2 nm to 4.9 nm with surface roughness decreased from 0.05μm to 0.03μm.All coatings showed residual compressive stress.When the pulse off time was fixed at 40μs,the grain sizes of the coatings decreased to the minimum of 4.9 nm with the highest hardness of22 GPa.The Cu-Nb nanocomposite coatings had similer diffuusive peak as mention above.The distribution of Cu、Nb elements in the coatings was also uniform without obvious segregation.By increasing the pulse off time,the composition of Nb in the coatings decreased from 68.75%to 64.62%with surface roughness decreased from 0.04μm to 0.02μm.All coatings showed residual compressive stress.When the pulse off time was 20μs,the highest coatings hardness achieved 14 GPa.Through comparing the surface quality and mechanical properties coatings,nano-Nb and Cu-Nb nanocomposite coatings process were selected.Nb coatings should be deposited under fixed micro pulse on-time of 8μs and the micro pulse off-time of 40μs with grain sizes of Nb coatings 4.9 nm and surface roughness Ra of 0.03μm.Meanwhile,the residual compressive stress was 1.63.GPa,the hardness and young’s modulus reached its maximum of 22 GPa and266 GPa.Cu-Nb nanocomposite coatings could be achieved under the micro pulse off-time of30μs,and on-time of 14μs,and the surface roughness Ra was 0.04μm,and the residual compressive stress of the coatings was 1.79 GPa.Meanwhile,the hardness and young’s modulus of the coatings reached its maximum of 16 GPa and 201 GPa.