Austenitic Stainless Steel Substrate Research Articles

Silver nanoparticles encapsulated in carbon cages obtained by co-sputtering of the metal and graphite

We have synthesized C–Ag thin films by co-sputtering of a silver–graphite target. The deposition temperature ranged from 77 K to 773 K, the silver concentration varying from 10 to 71 at%. The microstructure of the films has been characterized by transmission electron microscopy (TEM) and small-angle X-ray scattering under grazing incidence (GISAXS) experiments. It is shown that homogeneously distributed silver nanoparticles, having an elongated shape along the direction of the thin film growth, are formed within a more or less graphitized carbon matrix. After liquid nitrogen and room temperature depositions, a preferential crystallographic orientation is observed, dense (111) silver planes being at 90° with respect to the surface layer whereas the carbon matrix is amorphous. A graphitization leading to the encapsulation of the silver nanoparticles in graphite-like carbon has been obtained when the depositions were performed at 773 K for lower silver concentrations without ion-beam assistance and below 573 K for upper silver concentrations with ion-beam assistance. We propose that the demixing of carbon and silver occurs during the co-deposition process by surface diffusion of C and Ag atoms. It is inferred that the presence of silver simply serves as a “catalyst” for the graphitization process at these relatively low temperatures. Furthermore, we have investigated the tribological properties of our C–Ag coatings: a substantial increase in the wear resistance and a significant decrease in friction relative to an austenitic stainless steel substrate is observed.

Simultaneous chromizing-aluminizing diffusion coating of austenitic stainless steel by a two-step CVD process

Chromium and aluminum were simultaneouslydeposited by diffusion into austenitic stainless steelsubstrates by the pack-cementation process. Diffusionwas carried out in two different thermal runs (one- and two-step processes) and the results arepresented. The effects of various pack chemistries onthe coating characteristics of 310S and 316 stainlesssteel were also investigated. The major controlling factor to achieve the desired coatings was thecomposition of the masteralloy, particularly, thealuminum activity in the pack. A more uniform coatingwas achieved on 316 than on 310S for the same coating conditions due to the austenite-stabilizationeffect of Ni, which is less abundant in 316. The bestcoating condition in the range examined was with a packcomposed of 80Cr-20Al masteralloy and 2wt.%NH4Cl activator by the two step process.

Diagnostic of arc discharges for plasma nitriding by optical emission spectroscopy

A new high current (100–300 A), low voltage (25–45 V) and low pressure (0.4–1 Pa) arc discharge plasma used for steel nitriding is presented and characterized by optical emission spectroscopy (OES). In this process, the nitriding rate is high even if the workpieces are nitrided at floating potential without hydrogen in Ar−N 2 gas mixtures. With H 2, there is no appreciable gain in nitrogen content or in growth rate of the diffusion layer. In this paper, the OES diagnostic technique has been used to characterize the different excitation processes of both neutral and ionic argon species in Ar−N 2, Ar−H 2 and Ar−N 2−H 2 gas mixtures. The reactivity of this process is evaluated by using AISI 316 L austenitic stainless steel substrates nitrided for different treatment times at 690 K.

Spray diffusion: new method for surface modification combined with thermal spray and heat treatment

This paper describes post-heat treatment reaction diffusion between thermal sprayed aluminium and several kinds of substrate. The alloy layer formedby the spray diffusion process depends strongly on the composition of the substrate. It was found that appropriate surface properties can be obtained by selecting substrates of suitable composition and/or byselecting appropriate interlayers between the substrate and aluminium top coating. First, formation of alloy phases between an aluminium spray coating and a pure iron or plain carbon steel substrate by spray diffusion was examined in order to obtain fundamental information. Second, an 18Cr–8Ni austenitic stainless steelsubstrate was selected for testing. Finally, interdiffusion of multiple layered coatings with Ni–Cr–Mo alloys and aluminium on to stainless steel substrates was investigated.

Microstructure and oxidation-resistance of Ti 1 − x − y −zAl xCr yY zN layers grown by combined steered-arc/unbalanced-magnetron-sputter deposition

Cation-substituted Ti 1 − x − y −z Al x Cr y Y z N alloys, with y = 0.03 and z = 0.02, have been shown to offer greatly enhanced high-temperature oxidation resistance compared to presently used TiN and Ti 1 − x Al x N films. Layers (3 μm thickness) were deposited by unbalanced magnetron sputter deposition onto austenitic stainless steel and M2 high-speed steel substrates which had been ion etched in situ using a steered Cr-metal-ion cathudic arc discharge at an Ar pressure of 6 × 10 −4 mbar (0.45 mTorr). The metal ion-etching promoted initial local epitaxy on individual substrate grains while the overall film texture evolved through competitive growth to (111) in Ti 0.44Al 0.53Cr 0.03N alloys and (200) in Ti 0.43Al 0.52Cr 0.03Y 0.02N. Although Ti 0.44Al 0.53Cr 0.03N layers exhibited a columnar microstructure similar to that previously observed in Ti 1 − x Al x N alloys, the addition of 2 mol% YN resulted in significant grain refinement giving rise to a more equiaxed structure. The Knoop microhardness of Ti 0.43Al 0.52Cr 0.03Y 0.02N alloys was HK 0.025 = 2700 kg mm −2 compared to 2400 kg mm −2 for Ti 0.44Al 0.53Cr 0.03N. The onset of rapid oxidation, as determined from thermo-gravimetric measurements, ranged from ≈ 600 °C for TiN to 870 °C for Ti 0.46Al 0.54N to 920 °C for Ti 0.44Al 0.53Cr 0.03N to 950 °C for Ti 0.43Al 0.52Cr 0.03Y 0.02N.

Effect of temperature and sliding velocity on TiN coating wear

Dry sliding wear experiments at specific temperatures ranging between 25 and 500 °C were conducted on a PVD (reactive ion plated) TiN coating deposited onto an austenitic stainless steel substrate. The coating was worn against high-speed steel pins using a pin-on-disc sliding configuration at a low contact load (10 N) and various sliding speeds. Three wear regimes were identified: (1) at low temperatures and sliding speeds up to ~ 1.0 m s −1, there was minimal damage to the ion-plated TiN and the formation of a protective iron oxide transfer layer on the TiN surface; (2) at temperatures in the ~200–450 °C range, polishing of the TiN occurred, accompanied by increased wear rates as speed was increased; (3) above ~450 °C ductile deformation and failure of the coating occurred. Steel pin wear rates dropped significantly and the wear track was coated with a titanium/iron oxide transfer layer. The wear rate data are summarised in map form on temperature vs. sliding speed axes and discussed together with corresponding SEM, EDS and optical metallographic evidence.

Structure and properties of NbN and TaN films prepared by ion beam assisted deposition

Niobium nitride NbN x and tantalum nitride TaN x films were deposited on 316L austenitic stainless steel and silicon wafer substrates by evaporation of niobium and tantalum under simultaneous nitrogen ion irradiation, applying an acceleration voltage between 2 and 20 kV. In order to study the influence of the nitrogen content, the atom-to-ion transport ratio Nb, Ta/N was varied. The compositional and structural characterization of the films were carried out using Auger electron spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction and transmission electron microscopy. It was observed that the surface morphology strongly depends on the deposition conditions. X-ray diffraction patterns showed that the crystal structure of the films was changed from nitride to solid solution when the transport ratio was increased from 1 to 10, respectively. The crystal structure of the films deposited at Nb, Ta N = 6 and 10 had the feature of a nitrogen supersaturated bcc solid solution. Electron diffraction revealed the coexistence of an amorphous phase and a fine structured nitride phase in these films. The chemical bonding state of metal atoms observed by XPS changed with increasing the transport ratio, whereas the bonding state of nitrogen atoms was independent of the transport ratio. The corrosion behavior was evaluated in an oxygen saturated 5% sulfuric acid solution, using multisweep cyclic voltammetry measurements. The best corrosion protection was observed for the NbN film at an transport ratio of Nb N = 2 and for the TaN solid solution at Ta N = 6 .

Cobalt based alloy thick coatings by CDS process

The continuous detonation spray (CDS) process is one of the most recently developed coating processes andallows the production of thick coatings. This paper examines the correlation between process parameters and the properties of WC–17Co coatings deposited by CDS on an austenitic stainless steel substrate. Among the parameters considered the most important are the oxygen and propane flowrates and the ratio between them, and the distance between the torch nozzle and the surface to be coated. The first three affect the amount of process heat generated, while the last affects the interaction between the flame and the sprayed powders, determining the heating rate and final temperature. Coatings were evaluated in terms of porosity, surface roughness, hardness, and wear resistance.

Preparation of amorphous carbon thin films by ion beam assisted ECR-plasma CVD

Amorphous carbon thin films have been deposited on austenitic type stainless steel, glass and silicon wafer substrates by ion beam assisted ECR-plasma CVD from CH 4 gas as precursors. During the deposition the films were irradiated with Ar ions with an acceleration voltage of 0.5–4 kV. The composition and structure of the films were investigated by Raman and Fourier Transform Infrared (FT-IR) spectroscopies. The hardness and friction coefficients of the films were estimated by a dynamic ultra micro-hardness tester and a reciprocating sliding tester, respectively. The results showed that the structure and properties of the films strongly depended on the ion energy and the current density. The structure of the films changed from polymer to amorphous carbon with increasing ion energy and ion current density and the films were mainly composed of sp 3 and sp 2 carbon bonded to hydrogen. The integrated intensity ratio of amorphous carbon and disordered graphite structure, I D I G , increased from 0.6 to 1.9 with current density. The carbon films irradiated with high ion energy showed high hardness and a very low friction coefficient of 0.035.

Dry sliding wear of a PVD TiN coating against Si 3N 4 at elevated temperatures

Dry sliding wear experiments at specific temperatures ranging between 25 and 600°C were conducted on a PVD TiN coating deposited onto an austenitic stainless steel substrate. The coating was worn against Si 3N 4 balls using a ball-on-disc sliding configuration at a low contact load (11.6 N). At room temperature both surfaces became smooth with the formation of tribological layers containing Si and O on the TiN wear track. Metallographic evidence suggested that polishing wear of the coating occurred at 25°C accompanied by tribochemical breakdown of the Si 3N 4. At 100°C an 80% drop in the wear rate of Si 3N 4 was observed. The worn surfaces of the TiN were rough and a deep central groove was formed. It was proposed that at temperatures above 100°C damage of the TiN arose from high ball contact stresses due to reduced ball wear and increased thermal softening of the coating and substrate. Coefficient of friction values decreased above 400°C. This was attributed to the formation of TiO x products which acted as a lubricant.

Synthesis and properties of tantalum nitride films formed by ion beam assisted deposition

Tantalum nitride films TaN x were deposited onto 316L austenitic stainless steel and silicon wafer substrates by evaporation of tantalum under simultaneous nitrogen ion irradiation, applying an acceleration voltage of 2 kV. In order to study the influence of the nitrogen content, the atom-to-ion transport ratio ([Ta]/[N]) was varied. The compositional and structural characterization of the films was carried out using Auger electron spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray diffraction. It was observed that the surface morphology depends on the deposition conditions. X-ray diffraction patterns show the crystal structure of the films changing from Ta 3N 5, TaN, Ta 2N and Ta-N solid solution when the transport ratio is increased from 0.7 to 10. The crystal structure of the film deposited at [Ta]/[N]= 6 has the feature of a b.c.c. phase plus an amorphous phase containing 30 at. % nitrogen. The chemical bonding state of tantalum atoms observed by X-ray photoelectron spectroscopy changes with increasing transport ratio [Ta]/[N], whereas the bonding state of nitrogen atoms is independent of the transport ratio. The sheet resistivity and the temperature coefficient of resistance (TCR) of the films were measured by the four-point probe method. The TCR values of all observed TaN x films were negative, showing a minimum value at the lowest observed value of [Ta]/[N]= 0.7. The corrosion behavior was evaluated in an oxygen saturated aqueous solution of sulfuric acid, using multisweep cyclic voltammetry measurements. The best corrosion protection was observed for the Ta-N solid solution film prepared at [Ta]/[N] = 6. All other films, existing in the compound state, show less resistivity.

Adhesion and structural changes of multi-layered and multi-doped a-C:H films during annealing

High residual stress in hydrogenated amorphous carbon (a-C:H) films makes them rather difficult to integrate to substrates whose reactivity for carbide formation is low at the deposition temperature. Additionally, when exposed to thermal cycling, a-C:H films not only soften (i.e., graphitization), but also peel off because of thermal stresses. To improve adhesion and reduce the graphitization at high temperatures, we studied multi-element doped a-C:H films with multi-layered buffer structures on austenitic stainless steel substrates. A multi-layered structure was deposited in the order of TiC/ TiCN/TiN/Ti/stainless steel prior to depositing multi-element doped a-C:H films using dc reactive sputtering and plasma-enhanced CVD methods. The a-C:H films were doped with Ti and Si. Chemical analyses of the multi-layer structure was performed using X-ray photoelectron spectroscopy. Adhesion of the films with the multi-layered buffers was better than those without buffer layers at high temperatures ( T = 600 ° C). The critical scratching load was maximum at around 400 °C on (Si:Ti)-a-C:H films. Similarly, as observed by Raman spectroscopy Si:Ti doped films had higher resistance to the graphitization than undoped films.

ChemInform Abstract: Microstructure and Oxidation‐Resistant Property of Sol‐Gel‐Derived ZrO2‐Y2O3 Films Prepared on Austenitic Stainless Steel Substrates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis and corrosion properties of silicon nitride films by ion beam assisted deposition

Silicon nitride films SiN x were deposited on 316L austenitic stainless steel substrates by silicon evaporation and simultaneous nitrogen ion irradiation with an acceleration voltage of 2 kV. In order to study the influence of the nitrogen content on changes in stoichiometry, structure, morphology, thermal oxidation behaviour and corrosion behaviour, the atom to ion transport ratio was systematically varied. The changes of binding states and the stoichiometry were evaluated with XPS and AES analysis. A maximum nitrogen content was reached with a Si N transport ratio lower than 2. The films are chemically inert when exposed to laboratory atmosphere up to a temperature of more than 1000°C. XRD and SEM measurements show amorphous and featureless films for transport ratios Si N from 1 up to 10. The variation of the corrosion behaviour of coated stainless steel substrates in sulphuric acid and hydrochloric acid shows a minimum at medium transport ratios. This goes parallel with changes in porosity and adhesion. Additional investigations showed that titanium implantation as an intermediate step improves the corrosion resistance considerably.

Characterisation of TiN films prepared by electron shower, arc ion‐plating and sputtering methods

AbstractIt has been found that TiN films with high wear resistance and high adhesion can be prepared by electron shower deposition and arc ion plating on glass and austenitic stainless steel (SUS 316) substrates. The high wear resistance is principally explained by the grain size and surface morphology. Fine {100}‐faceted crystals (10–150 nm) grew on the surface. The typical morphology of the crystals was triangular pyramidal. The crystallite size was changed by the bias voltage. Faceted crystals produced by arc ion plating were rounded and smoothed by a change in bias, but were unaltered in samples prepared by the electron shower process. The fine faceted surfaces had higher wear resistance than the granularly rounded ones. When TiO2 was formed at the interface of the glass substrate, the adhesion was lowered. The high‐adhesion film prepared by electron shower deposition contained a small amount of TiO2 at the interface.

Microstructure and Oxidation‐Resistant Property of Sol‐Gel‐Derived ZrO2‐Y2O3 Films Prepared on Austenitic Stainless Steel Substrates

The effect of Y2O3 addition to the oxidation resistance of sol‐gel‐derived zirconia films coated on austenitic stainless steel substrates was examined. The oxidation weight gain measurement and XRD analyses of oxides showed that addition of Y2O3 reduces oxide formation. TEM observations revealed that the films are joined to the substrates via an amorphous layer with concentrated Si, and the layer grew thicker by adding Y2O3 or elevating the firing temperature. Lattice constants of the films were shown to be more expanded than the zirconia powders prepared from the coating liquids.

Modification of the Structure-Phase State of Coatings by Ion Implantation Techniques

AbstractTransmission electron microscopy was used to study the effect of nitrogen-ion irradiation on the microstructure of ion-plasma TiN coating deposited on a substrate of austenitic stainless steel. The principal peculiarities of the changes in the fine structure at the substrate-coating interface and in the bulk of the coatings having a thickness of several micrometers have been revealed for the conditions of ion-beam-assisted deposition and plasma-assisted deposition. Possible mechanisms for the effect of ion irradiation on the microstructure of the substrate-coating composition are discussed.

アルミニウムを溶射したオーステナイト系ステンレス鋼の熱処理に伴う合金層の生成

アルミニウムを溶射したオーステナイト系ステンレス鋼の熱処理に伴う合金層の生成

Metallurgical study of low-temperature plasma carbon diffusion treatments for stainless steels

We recently reported a novel low-temperature carbon diffusion technique forsurface hardening of stainless steels. The treatment was shown to provide benefits in terms of abrasive wear resistance. There is also evidence to suggest that by performing diffusion treatments at low temperatures ( i.e. below 400°C), these benefits can be achieved without compromising corrosion resistance. Here a variety of surface analysis and depth profiling techniques have been used to determine the physical and mechanical properties of carbon-rich layers produced on a range of stainless steel substrate materials. X-ray diffraction (XRD) was employed to determine the crystallographic structure, whilst wavelength dispersive X-ray analysis (WDX) and glow discharge optical spectroscopy (GDOS) gave information on the concentration and distribution of the diffused species within the treated layers. A variety of carbide-based structures was detected, including the expected M 23C 6 and, more surprisingly, M 3C. Optical and electron microscopy techniques were used to provide information on layer morphology. The surfaces produced by the low-temperature carbon-diffusion process generally exhibit a distinct diffusion layer of between 1 and 20 μm, depending on the material and the treatment conditions. Austenitic stainless steels appear to give the best response to treatment, however other types of stainless steel can be treated, particularly if the microstructure contains above 5% retained austenite. Here we discuss the changes in mechanical and metallurgical properties provided by this technique and its potential value for treatment of both austenitic and other stainless steel substrate materials.

The crystal structures of stainless steel films sputter-deposited on austenitic stainless steel substrates

Sputter deposited austenitic stainless steels, AISI 304 and 316, almost always result in films having crystalline structures different from the parent material when the deposition temperature is below 648 K. The earlier investigation showed when 316L-SS films were sputter-deposited on glass substrates at room temperature, they contained a mixture of two phases, a ferrite like bcc phase and a hexagonal phase bearing a resemblance to [epsilon]-martensite. Sputter deposition of 304-SS performed at 77 K on rock salt resulted in an amorphous structure; however, when deposited at room temperature, it yielded a structure that could not be indexed either as bcc or as fcc. Thus, in general for AISI 304 or 316 compositions, low temperature depositions result in films with bcc crystal structure, whereas high temperature depositions yield fcc films. In addition to the temperature dependence, it is also relevant to question whether the substrate can influence the nature of the phases present in the films. In this paper, the authors address this question by changing the surface condition of the substrate. With this purpose they have selected a substrate of a similar nature to the target to be sputtered, 316L-SS, and varied the surface preparation.