Polished Stainless Steel Substrates Research Articles

Cavitation and abrasion resistance of Ti–Al–Y–N coatings prepared by the PIII&D technique from filtered vacuum-arc plasma

In the present work we examined the cavitation and abrasion resistance of PIII&D Ti–Al–Y–N coatings with Y content ≤1at.% and analyzed the influence of mechanical properties and structure of the coatings on their wear resistance. The coatings with thickness of 5–6μm were deposited on the polished stainless steel (type-302) substrates by filtered vacuum-arc evaporation technique. The substrate potential was either DC with a constant voltage of −150V or pulsed DC with an amplitude AU in the range of 0–2.5kV. The cavitation treatment of the coating deposited at the DC potential resulted in long cracks on their surface. The coating deposited at AU=0 was subjected to pitting erosion. The high voltage pulsed substrate potential contributed to the decrease in the rate of mass loss under cavitation, at the same time the quantity of erosion defects on the treated surface was strongly diminished. The increase of Y content resulted in improvement of wear durability. Average rates of cavitation and abrasion wear of (Ti,Al)N+1at.%Y were a factor of 3 to 5 times lower than that of (Ti,Al)N and tenfold lower than that of TiN. Formation of a dense nanostructure with fine grains and non-evident (inapparent) columnar morphology, significant reduction in the surface roughness and decrease in the internal stress level are the reasons for the improved wear resistance.

Inductively coupled oxygen plasma in H mode for removal of carbon from mixed a-C:H, W films

A method for selective removal of carbon from mixed deposits of tungsten and hydrogenated amorphous carbon films likely to be deposited in fusion reactors with divertors containing carbon and tungsten tiles has been elaborated. Mixed deposits were prepared on highly polished stainless steel substrates by sputtering of a tungsten target in acetylene-rich atmosphere. Samples were exposed to fully dissociated non-equilibrium oxygen plasma created by inductively coupled electrodeless radio frequency discharge created in pure H-mode. Auger electron depth profiling was applied for determination of the compositional changes upon plasma treatment. Carbon from about 200nm thick mixed deposit has been removed effectively in about 45s of plasma treatment. Further treatment caused inter-diffusion of sample elements until a rather uniform W, Fe, O film was formed on substrates. The same samples treated by plasma created with the discharge in E-mode did not affect the composition of coatings even after treatment for 15min indicating important advantages of H-mode discharges.

Effect of Ag-Doping on the Capacitive Behavior of Amorphous Manganese Dioxide Electrodes

Amorphous MnO2 and Ag-doped MnO2 thin films were galvanostatically deposited on a polished stainless steel substrate from 20 mM KMnO4 aqueous solutions without and with AgNO3 additions at cathodic current density of 1 mA/cm 2 for the application in electrodes of electrochemical supercapacitors. The supercapacitive properties of the deposited thin films have been studied in 0.5 M Na2SO4 electrolyte by cyclic voltammetry, impedance spectroscopy, and charge-discharge measurement techniques. The Ag-free MnO2 film showed better capacitive behavior and lower charge transfer resistance compared to the Ag-doped MnO2 films. The specific capacitance and charge transfer resistance values for Ag-free MnO2 films were 160 F/g at a scan rate 10 mV/s and 3.87 Ω, respectively. Cyclic stability using charge-discharge measurement technique indicates the excellent stability of Ag-free MnO2 films and its possible use as a low cost electrode for superca- pacitor applications.

Effect of target–substrate distance onto the nanostructured rhodium thin films via PLD technique

Rhodium thin films on highly polished stainless steel substrates were fabricated via pulsed laser deposition (PLD) technique. The PLD films of rhodium were observed to be preferentially oriented in Rh(111) plane. The films showed dense columnar structure of nanometric crystallites. The effects of target–substrate distance onto the root mean square roughness, crystal structure, reflectivity and thickness of the PLD rhodium films were investigated.

Thermal stability of nitride solar selective absorbing coatings used in high temperature parabolic trough current

This paper reports a new efficient solar selective surface in high temperature application. The influence of the monolayer’s microstructure and deposition rate was firstly discussed. Then the nitride nano-multilayer on the polished stainless steel (herein after referred as “SS”) substrate was prepared with Ti and Al metal targets by DC. and R.F. magnetron co-sputtering. The samples were annealed in air at different temperatures ranging from 350 to 800°C for 2 h to evaluate their thermal stability. The samples’ surface and cross-section morphology, crystal structure, phase composition, optical properties were analyzed by scanning electron microscopy, X-ray diffraction, UV-VIS-NIR spectrophotometer and infrared emissivity tester. The results show that the coatings exhibit high solar selectivity (α/ɛ) of 0.943/0.08 even after heat-treatment up to 400°C for 2 h in air. After heat-treatment at 600°C in air, the solar selectivity decreases to 0.92/0.16.

Comparison of sliding wear behaviour of pulse electrodeposited Ni–Cu nanocrystalline alloys and Ni–Cu/Cu multilayers

This study presents a comparison of tribological properties of electrodeposited nanolayered Ni–Cu/Cu multilayers and nanocrystalline Ni–Cu alloys. In this work, nanocrystalline Ni–Cu alloys containing 35·8 and 26·0 wt-%Cu with grain sizes of 12·8 and 6·6 nm respectively were chosen for wear tests in which the tribological performances of these alloys were compared with Ni–Cu/Cu multilayers: [Ni–Cu (4·5 nm)/Cu (1·97 nm)]n (30·4 wt-%Cu) and [Ni–Cu (7·8 nm)/Cu (1·97 nm)]n (20·2 wt-%Cu) respectively. All the test samples were electrodeposited under pulsed current conditions on polished stainless steel substrates keeping total thickness fixed at ∼10 μm. Reciprocating dry sliding experiments of these samples at a constant normal load in the range 3–11 N were performed in ball on plate geometry keeping the amplitude fixed at 0·001 m. The obtained average coefficient of friction of nanocrystalline alloys was found to be slightly inferior compared to that of multilayers. On the other hand, the wear rate of nanocrystalline alloys was lower than that of multilayers under identical conditions. Higher hardness and lower elastic modulus of nanocrystalline alloys compared to that of multilayers was found to be responsible for the observed wear rate variation.

Deposition Behavior of Copper Fine Particles onto Flat Substrate Surface in Cold Spraying

Cold spray is a promising process to fabricate high-quality metallic coatings. However, it is necessary to improve some properties, especially the adhesive strength of the coating to the substrate to clarify deposition mechanism of the solid particles onto substrate surface. In this study, deposition behavior of the cold sprayed copper fine particles was observed precisely and the adhesive strength of the coating was evaluated. The deposition behavior of the sprayed individual copper particles on mirror polished stainless steel substrate was fundamentally investigated. The interface microstructure between sprayed particle and substrate revealed that an amorphous-like band region was recognized at interface during coating fabrication at high power conditions. For the deposition mechanism of the cold sprayed particles onto substrate surface, it was indicated that the deformation of the particles initially induce the destruction of its surface oxide and an appearance of the active fresh surface of the material may enhance the bonding between particles and substrate. On the other hand, in coating fabrication at high power condition, bonding between particle and substrate may be possibly formed via oxygen-rich amorphous-like layer at interface.

Study of the Splat-Substrate Interface for a NiCr Coating Plasma Sprayed onto Polished Aluminum and Stainless Steel Substrates

In the plasma spraying process, the mechanisms by which molten particles impact on and bond with the substrate are not fully understood. For this study a nickel-chromium powder was sprayed onto mirror polished aluminum 5052 and stainless steel 304 substrates to form single splats. The splats and their interface with the substrate were studied using detailed microstructural characterization with emphasis on the shape of the splats, the nature of the splat-substrate interface, including the degree of contact and the extent of melting of the substrate and mixing with the splat material, and the presence, either on or within the splats of phases such as oxides. It was shown that melting of the substrate, along with intermixing and diffusion between substrate and splat materials, occurred for the steel substrate, but not for the aluminum substrate. Oxides including nickel oxide, chromium oxide, and aluminum oxide were also observed, the type and distribution of these phases depended on the substrate type.

Study of the effects of surface chemistry on splat formation for plasma sprayed NiCr onto stainless steel substrates

The plasma spray process involves the melting and spraying of a fine powder onto a substrate using a plasma jet. However, understanding of the processes of splat formation and bonding with the substrate is limited because of the difficulties in performing high resolution studies of the splat–substrate interface. In this study, a nickel–chromium powder was sprayed onto mirror polished stainless steel substrates that have undergone various thermal and boiling pre-treatments to modify their surface chemistry. Detailed microstructural characterization of the splats and their interfaces with the substrate was performed using several electron microscopy techniques. Splats' shapes, the nature of the splat–substrate interface and occurrence of substrate melting and chemical intermixing, along with the presence of various oxide phases (Ni, Fe and Cr oxides) were observed and discussed in relation to the splat formation process. Such features were found to vary depending on the surface chemistry of the substrate.

Evidence of Substrate Melting of NiCr Particles on Stainless Steel Substrate by Experimental Observation and Simulations

Single NiCr splats were plasma-sprayed onto a polished stainless steel substrate held at room temperature. The splat-substrate interface was characterized by focused ion beam and transmission electron microscopy. The frequent observation of NiO particles, particularly in pores within the splat, and at the periphery of splat, suggests that the principal oxidation process occurs at the substrate surface, where the splats are exposed to a water vapor-rich environment. It was also observed that the splat adhered well in some locations where elemental-diffusion and jetting of the substrate occurred, suggestive of substrate melting. A three-dimensional numerical model was developed to simulate the impact of a splat onto a substrate. The simulation shows that the observation of the central pore in the splat and the phenomenon of substrate melting may occur. Based on these results, the effect of water release on oxide formation and splat morphology can be explained.

Pulsed laser deposition of lanthanum phosphate protective films

Pulsed laser deposition (PLD) technique has been successfully employed to generate thin film coating of lanthanum phosphate on various substrates. Sintered targets of lanthanum phosphate were ablated using pulsed Nd:YAG laser radiation. Although, coatings generated by PLD on polished stainless steel substrates, as well as on optically polished quartz samples were found to be uniform and having good homogeneity, the coatings had poor adhesion characteristics with the substrate surface. However, PLD based coating on surface treated stainless steel substrates (either sandblasted or having a pre-coating of NiCrAlY alloy) showed strong bonding with the substrate surface. Structural investigation of the deposited films under scanning electron microscope revealed high level of homogeneity and absence of porosity. PLD based thin film coatings of lanthanum phosphate were observed to be superior in terms of their microstructural characteristics in comparison to plasma based coatings that had a distinctly higher level of residual porosity. Our results suggest that a combination of a thick plasma based coating followed by a PLD based thin overcoat, both of lanthanum phosphates, would result in an effective protective coating that is dense enough to accomplish the function of isolating the substrate from a corrosive environment. Such coatings when deposited on the inside of crucibles would facilitate containment of liquid uranium and other such corrosive liquids.

Defect effect on tribological behavior of diamond-like carbon films deposited with hydrogen diluted benzene gas in aqueous environment

This study examined the friction and wear behavior of diamond-like carbon (DLC) films deposited from a radio frequency glow discharge using a hydrogen diluted benzene gas mixture. The DLC films were deposited on Si (1 0 0) and polished stainless steel substrates by radio frequency plasma-assisted chemical vapor deposition (r.f.-PACVD) at hydrogen to benzene ratios, or the hydrogen dilution ratio, ranging from 0 to 2.0. The wear test was carried out in both ambient and aqueous environments using a homemade ball-on-disk type wear rig. The stability of the DLC coating in an aqueous environment was improved by diluting the benzene precursor gas with hydrogen, suggesting that hydrogen dilution during the deposition of DLC films suppressed the initiation of defects in the film and improved the adhesion of the coating to the interface.

Surface-initiated ATRP of PMMA, PS and diblock PS- b-PMMA copolymers from stainless steel modified by 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid

A new ATRP initiator, 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid, has been synthesized and grafted as a film on a mechanically polished stainless steel (ASI304) substrate. Molecular integrity of the grafted initiator in the film, alkyl chain ordering, wettability were determined by X-ray photoelectron spectroscopy, infrared, and water contact angles. Polystyrene, poly(methyl methacrylate) and diblock copolymer (polystyrene- b-poly(methyl methacrylate)) brushes have been grafted from the flat stainless steel surfaces through surface-initiated atom transfer radical polymerization (ATRP) and characterized to check the effectiveness of the new initiator for future uses in surface-initiated ATRP.

Li diffusion in spinel LiNi0.5Mn1.5O4 thin films prepared by pulsed laser deposition

Spinel LiNi0.5Mn1.5O4 thin film electrodes of 0.5 μm thickness were prepared on polished stainless steel (SS) substrates by pulsed laser deposition. Kinetics and mass-transport of Li intercalation/deintercalation were investigated by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and potentiostatic intermittent titration technique (PITT). The CV measurements indicate that there exists a small amount of Mn3 + in the film and Li transportation is controlled by diffusion at high scan rates. EIS measurements show a potential independent low charge-transfer resistance region between 4.1 and 4.7 V and a stable surface layer resistance through the full potential range. The chemical diffusion coefficients of Li in the LiNi0.5Mn1.5O4 thin film obtained by EIS and PITT have been found to be in the range of 10−12–10−10 cm2 s−1 depending on the electrode potential. Two minima were found for from PITT at potentials close to the peak potentials of the corresponding CV.

Mechanical properties of superhard TiB 2 coatings prepared by DC magnetron sputtering

Superhard titanium diboride (TiB 2) coatings ( H v> 40 GPa) were deposited in Ar atmosphere from stoichiometric TiB 2 target using an unbalanced direct current (d. c.) magnetron. Polished Si (0 0 1), stainless steel, high-speed steel (HSS) and tungsten carbide (WC) substrates were used for deposition. The influence of negative substrate bias, U s, and substrate temperature, T s, on mechanical properties of TiB 2 coatings was studied. X-ray diffraction (XRD) analysis showed hexagonal TiB 2 structure with (0 0 01) preferred orientation. The texture of TiB 2 coatings was dependent upon the ion bombardment ( U s increased from 0 to −300 V) and the substrate heating ( T s increased from room temperature (RT) to 700 °C). All TiB 2 coatings were measured using microhardness tester Fischerscope H100 equipped with Vickers and Berkovich diamond indenters and exhibited high values of hardness H v up to 34 GPa, effective Young's modulus E*=E/(1 –ν) ranging from 450 to 600 GPa; here E and ν are the Young's modulus and Poisson's ratio, respectively, and elastic recovery W e≈80%. TiB 2 coating with a maximum hardness H v≈73 GPa and E*≈580 GPa was sputtered at U s=−200 V and T s=RT. Macrostresses of coatings σ were measured by an optical wafer curvature technique and evaluated by Stoney equation. All TiB 2 coatings exhibited compressive macrostresses.

Effect of Droplet Characteristics and Substrate Surface Topography on the Final Morphology of Plasma-Sprayed Zirconia Single Splats

The morphology of atmospheric plasma-sprayed yttria-stabilized zirconia single splats has been studied. Single splats of plasma-sprayed ZrO2-7%Y2O3 powder have been collected on polished stainless steel substrates kept at three different temperatures (room temperature, 300 °C, and 600 °C). The effect of heating on the substrates’ surface topography was evaluated. The effects of spray process parameters such as substrate temperature, particle temperature, and velocity on the morphology of single splats was studied. Variation of splat shape with location within the footprint of plasma spray was investigated. Pore and microcrack formation, splashing behavior, splat/substrate, and splat/splat interfaces were analyzed. Splat morphology and diameter, satellite particles, and splashing behavior were recorded using both scanning electron microscopy and image analysis. Splat/substrate and splat/splat interfaces were studied from cross sections prepared by focused ion beam milling. Results showed primarily disk-shape morphology and no evidence of delamination along the splat/substrate interface at 600 °C substrate temperature. Overlapped splats showed evidence of melting (microwelding) at splat boundaries. Splat thickness was measured to be less than 1 μm for all spray conditions.

Magnetron sputtered Ti–Si–C thin films prepared at low temperatures

In this work, low temperature Ti–Si–C films were deposited onto silicon and polished stainless steel and high-speed steel substrates by DC magnetron co-sputtering from two Ti targets, one with C pellets and the other with Si pellets. The composition of the films was investigated by Electron Probe Micro-Analysis (EPMA), while structure was characterized using a conventional X-ray diffractometer. The hardness and residual stress were studied using depth-sensing indentation and substrate deflection measurements (using Stoney's equation), respectively. Plots of both C/Ti and Si/Ti atomic ratios as a function of the targets current ratio showed the existence of two distinct regions: (i) a silicon rich zone (target current ratios, I Ti–C/ I Ti–Si, up to 0.5, Si/Ti atomic ratios in the range of 0.21–0.27 and low C/Ti atomic ratio, < 0.17), and (ii) a carbon rich zone (films were prepared with target current ratios, I Ti–C/ I Ti–Si, between 1.4 and 2.9, with C/Ti atomic ratio in the range of 0.29–0.34 and low Si/Ti atomic ratio). These two composition regions were found to be of particular influence in all scanned properties. Structural analysis revealed the possibility of the coexistence of different phases in the prepared films, namely a sub-stoichiometric fcc NaCl-type TiC structure and a Ti metallic phase (α-Ti or β-Ti). The coatings with highest carbon content (carbon rich zone), exhibit mainly a sub-stoichiometric fcc NaCl TiC-type structure. The films within the silicon rich zone show a progressive tendency for amorphization. The existence of some C or even Si(C) amorphous tissues cannot be excluded. The residual stress states ( σ r) and the hardness values ( H) were relatively low, σ r < − 1 GPa and H = 7–11 GPa, respectively, which could be a consequence of the low crystallinity order exhibited by the coatings and/or due to the high amounts of Ti in the coatings.

320 コールドスプレーしたCu粒子の付着におよぼす基材温度の影響(OS13-1 コールドスプレー皮膜の付着メカニズムとその皮膜特性,OS13 コールドスプレー皮膜の付着メカニズムとその皮膜特性)

Self designed cold spray equipment was installed in the laboratory and deposition behavior of sprayed individual metallic particles on the substrate surface was fundamentally investigated. As a preliminary experiment, pure Cu particles were sprayed on mirror polished stainless steel substrate surface. Particles diameter, process gas, gas pressure, gas temperature and substrate temperature were systematically changed as the process parameters, and effect of these parameters on the flattening or deposition behavior of an individual particle was investigated. From the results obtained, it was found that the deposition temperature is a possible domination on the deposition behavior in cold spray process.

コールドスプレー法における銅粒子堆積機構の解明

Application of cold spray process is expected in the various industrial fields such as automobile, aircraft and electronics. So many investigations for practical application have been actively performed in many research organizations. However, as the process has just started in these days, fundamental aspect like deposition mechanism itself has not been well understood up to today. To establish the higher reliability or controllability of the cold spray process, fundamental research, especially on the deposition mechanism, may become a key for the process development. We tried the clarification of particle deposition mechanism in cold spray process by experimental approach. In this study, deposition behavior of sprayed individual particle onto substrate surface was investigated precisely.Self designed cold spray equipment was installed in the laboratory and deposition behavior of sprayed individual metallic particles on the substrate surface was fundamentally investigated. As a preliminary experiment, pure Cu particles were sprayed on mirror polished stainless steel substrate surface. Particles diameter, process gas, gas pressure, gas temperature and substrate temperature were systematically changed as the process parameters, and effect of these parameters on the flattening or deposition behavior of an individual particle was investigated.

Electrochemical studies of low-temperature processed nano-crystalline LiMn 2O 4 thin film cathode at 55 °C

LiMn 2O 4 thin films with nano-crystals less than 100 nm were successfully grown on polished stainless steel substrates at 400 °C and 200 m Torr of oxygen by pulsed laser deposition. A maximum discharge capacity of 62.4 μAh cm −2 μm −1 cycled between 3.0 and 4.5 V with a current density of 20 μAh cm −2 was achieved. The effect of several overdischarge cycles was negligible, and both the effect of Jahn–Teller distortion at low potentials on capacity loss and structure instability at high potentials were effectively inhibited in this nano-crystalline film, resulting in an excellent cycling stability with a very low fading rate of capacity up to 500 cycles at 55 °C.