Substrate and morphology effects on photoemission from core-levels in gold clusters

NRC publication: Ye

Effect of C/Si Ratio on the Electrochemical Behavior of a-SiCx:H Coatings on SS301 Substrate Deposited by PECVD

Amorphous hydrogenated silicon carbide (a-SiCx:H) coatings were deposited on stainless steel 301 (SS301) using plasma enhanced chemical vapor deposition with the methane gas flow ranging from 30 to 90 sccm. XRD spectra confirmed the amorphous structure of these coatings. The as-deposited coatings all exhibited homogenous dense feature, and no porosities were observed in SEM and AFM analysis. The a-SiCx:H coatings remarkably increased the corrosion resistance of the SS301 substrate. With the increase of the C concentration, the a-SiCx:H coatings exhibited significantly enhanced electrochemical behavior. The a-SiCx:H coating with the highest carbon concentration acted as an excellent barrier to charge transfer, with a corrosion current of 3.5×10-12 A/cm2 and a breakdown voltage of 1.36 V, compared to 2.5×10-8 A/cm2 and 0.34 V for the SS301 substrate

Hybrid Co-Cr/W-WC and Ni-W-Cr-B/W-WC coating systems

The aim of this study was to investigate the effects of subsurface materials on the performance of a wear-resistant thin film. The mechanical, tribological, and corrosion properties were assessed for two hybrid coating systems: (1) W-WC thin film and a laser cladded Co-Cr interlayer applied to a 316 stainless steel substrate and (2) the same W-WC thin film and a spray-and-fused Ni-W-Cr-B interlayer applied to an Inconel\uae 718 substrate. They were then compared to the same systems without an interlayer. The microstructures were analyzed by XRD, EDS, and SEM. The hardness and surface load-carrying capacity of the coating systems were determined by micro- and macrohardness testing. Rockwell indentation was used to assess coating adhesion (CEN/TS 1071-8). Tribological properties were assessed with a reciprocating tribometer, and corrosion resistance was determined by potentiodynamic polarization and electrochemical impedance spectroscopy. The originality of this work lies in the finding that, except for the Inconel 718/Ni-W-Cr-B/W-WC system, the wear rate decreases with decreasing hardness of the subsurface materials carrying the thin film due to the decreasing contact pressure for a given load. Another novel finding is the stress-induced phase transformation of the Co-Cr interlayer, which occurs beneath the thin film under high load.Peer reviewed: YesNRC publication: Ye

Structural, tribo-mechanical, and thermal properties of NbAlN coatings with various Al contents deposited by DC reactive magnetron sputtering

DC reactive magnetron sputtered Nb2AlyNx coatings with various Al contents (y/(y + z)) ranging from 0 to 0.75 were deposited using different ratios of the currents applied to the Al and Nb targets in order to systematically control their chemical composition and crystalline structure, and to enhance their mechanical, tribological and thermal stability performance. The film microstructure and properties were assessed by various complementary techniques such as electron probe microanalysis, X-ray diffraction, nanoindentation, ball-on-disc test, and scanning electron microscopy. It was found that the solubility limit of Al in the NbN lattice is in the range 0.44 0.44, the hardness of the Nb2AlyNx coatings is reduced due to the formation of the soft hexagonal MN phase. In addition, the coatings exhibit interesting tribological properties: the coefficient of friction is in the range of 0.74 to 0.85, and wear rate is in the range of 4.8-9.1 x 10(-6) mm(3)/ Nm. Thermal stability shows a dependence on the Al content; specifically, the Nb0.33Al0.17N0.50 coating was found to be thermally stable up to 700 degrees C

Design and Optimization of Erosion Resistant Coating Architectures Containing Superhard Layers

Peer reviewed: YesNRC publication: Ye

Design of Hard Coatings Architecture for the Optimization of Erosion Resistance

NRC publication: Ye