Introduction Thin coatings are generally designed and applied to modify the surface properties of bulk materials, thus protecting them from mechanical, physical or chemical damages [1,2]. In this study, an investigation on protective nitride films for harsh conditions, produced in CNR-IENI laboratories is presented. Thin films were deposited by High Power Impulse Magnetron Sputtering (HiPIMS) [3] that is an emerging Physical Vapor Deposition (PVD) technology, which produces an ultra-dense plasma, leading to a very high ionization degree of the sputtered material with respect to conventional magnetron sputtering techniques. The growth of ultra-dense coatings is promoted, with enhanced adhesion, in particular for complex-shaped surfaces, improved toughness, reduced columnar structure, residual stress and deposition temperature. Some applications were identified for the coatings with such improved properties: high temperature stage of gas turbine engines, internal combustion engines, pipeline for extreme corrosive environments. Materials and methods Several coatings (TiAlN, MoN, TaN) were deposited on innovative and traditional structural materials, as ?-TiAl, martensitic stainless steel (T91), AISI 304, AlSi alloy. Depending on coating specific application, appropriate characterization techniques were selected to investigate films properties. Morphologies, compositions and structures of the films were analyzed by FIB, SEM, EDS, XRD and optical microscopy. The mechanical and tribological characterization included hardness measurements by nano-indentation, adhesion evaluation by scratch tests, wear and friction tests under different loading conditions. Results and discussion As a difference from traditional PVD techniques, here nitride composites were obtained at low deposition temperature. Results from structural and mechanical characterization stated that HiPIMS technique is suitable for producing coatings with different properties by regulating process parameters. Indeed, in this context the desired film properties, which are peculiar for each selected application, were driven. Density was varied by acting on power, pressure, and substrate polarization; adhesion was improved by pretreating the substrate prior to deposition and reducing the mismatch of thermal expansion coefficient through the insertion of an interlayer; wear resistance was increased by modifying the H/E ratio. Conclusions HiPIMS technique allows the deposition of coatings with tailored properties. While optimizing deposition parameters like power, pressure and sputtering gas composition, pulse length and frequencies, bias voltage, temperature and system geometries it was possible to customize final properties of coatings. Acknowledgments This work was funded by the Italian National Research Council - Italian Ministry of Economic Development Agreement ''Ricerca di sistema elettrico nazionale''.
Hard protective nitride coatings for extreme conditions by HiPIMS
SM Deambrosis;V Zin;E Miorin;F Montagner;S Battiston;M Fabrizio
2015
Abstract
Introduction Thin coatings are generally designed and applied to modify the surface properties of bulk materials, thus protecting them from mechanical, physical or chemical damages [1,2]. In this study, an investigation on protective nitride films for harsh conditions, produced in CNR-IENI laboratories is presented. Thin films were deposited by High Power Impulse Magnetron Sputtering (HiPIMS) [3] that is an emerging Physical Vapor Deposition (PVD) technology, which produces an ultra-dense plasma, leading to a very high ionization degree of the sputtered material with respect to conventional magnetron sputtering techniques. The growth of ultra-dense coatings is promoted, with enhanced adhesion, in particular for complex-shaped surfaces, improved toughness, reduced columnar structure, residual stress and deposition temperature. Some applications were identified for the coatings with such improved properties: high temperature stage of gas turbine engines, internal combustion engines, pipeline for extreme corrosive environments. Materials and methods Several coatings (TiAlN, MoN, TaN) were deposited on innovative and traditional structural materials, as ?-TiAl, martensitic stainless steel (T91), AISI 304, AlSi alloy. Depending on coating specific application, appropriate characterization techniques were selected to investigate films properties. Morphologies, compositions and structures of the films were analyzed by FIB, SEM, EDS, XRD and optical microscopy. The mechanical and tribological characterization included hardness measurements by nano-indentation, adhesion evaluation by scratch tests, wear and friction tests under different loading conditions. Results and discussion As a difference from traditional PVD techniques, here nitride composites were obtained at low deposition temperature. Results from structural and mechanical characterization stated that HiPIMS technique is suitable for producing coatings with different properties by regulating process parameters. Indeed, in this context the desired film properties, which are peculiar for each selected application, were driven. Density was varied by acting on power, pressure, and substrate polarization; adhesion was improved by pretreating the substrate prior to deposition and reducing the mismatch of thermal expansion coefficient through the insertion of an interlayer; wear resistance was increased by modifying the H/E ratio. Conclusions HiPIMS technique allows the deposition of coatings with tailored properties. While optimizing deposition parameters like power, pressure and sputtering gas composition, pulse length and frequencies, bias voltage, temperature and system geometries it was possible to customize final properties of coatings. Acknowledgments This work was funded by the Italian National Research Council - Italian Ministry of Economic Development Agreement ''Ricerca di sistema elettrico nazionale''.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
