Surface Of Steel Substrate Research Articles

The applicability of ultra thin silicon films as interlayers for CVD diamond deposition on steels

In this study, the use of thin Si interlayers (35-150 nm) for promoting diamond deposition onto steel is investigated. The diamond films are deposited by hot filament CVD onto AISI type 316 stainless and high-speed steels. Single stage deposition at substrate temperatures ranging from as low as 475 to 750 °C is found to result only in non-continuous films with low number densities of diamond crystallites. A composite film of diamond and carbides is formed at intermediate temperatures of about 650 °C. It is believed that the formation of iron silicide phases at the exposed steel substrate surfaces leads to diffusion barriers for free iron from the steel matrix, so that graphitic soot formation is significantly avoided. Utilizing a two-stage deposition process, the density and uniformity of the deposited diamond films are increased and a nearly continuous cauliflower shaped diamond film is obtained. Micro-Raman spectroscopy, scanning electron microscopy and X-ray diffraction techniques are employed to study the phases, morphology, composition, quality and residual stresses of the grown diamond layers.

Kinetics of boriding of AISI W1 steel

A technologically interesting characteristic of boriding is the production of a hard, wear-resistant coating layer on the steel substrate. In this study, case properties of borided AISI W1 steel has been investigated by conducting a series of experiments in Ekabor-I powders at the process temperature of 1123–1323 K at 50 K intervals for periods of 1–8 h. The presence of borides FeB and Fe 2B formed on the surface of steel substrate was confirmed by optical microscopy and X-ray diffraction. Cross-sectional observation in the optical microscope revealed smooth and compact morphology of the borided layer. The distribution of alloy elements from the surface to the interior was confirmed by energy dispersive X-ray spectroscopy. The hardness of the boride layer formed on the surface of the steel substrate was higher than 1500 HV. It was concluded that the optimum temperature for AISI W1 steel borided in Ekabor-I powders was approximately 1223 K for hardness in 10 μm depth, and the hardness change with boriding temperature was related to the grain size of the treated steel. The kinetics of boriding show a parabolic relationship between layer thickness and process time, and the activation energy for the process is 171.2±16.6 kJ mol −1. Moreover, an attempt was made to investigate the possibility of predicting the iso-thickness of boride layer variation and to establish an empirical relationship between process parameters of boriding and boride layer.

Relaxation of Residual Stresses on the Near Surface of Carbon Steel Substrates due to Plasma Cleaning

Relaxation of Residual Stresses on the Near Surface of Carbon Steel Substrates due to Plasma Cleaning

Boriding response of AISI W1 steel and use of artificial neural network for prediction of borided layer properties

In the present study, boriding response of AISI W1 steel and prediction of boride layer properties were investigated by using artificial neural network (ANN). Boronizing heat treatment was carried out in a solid medium consisting of Ekabor-I powders at 850–1050 °C at 50 °C intervals for 1–8 h. The substrate used in this study was AISI W1. The presence of borides FeB and Fe 2B formed on the surface of steel substrate was confirmed by optical microscope and X-ray diffraction analysis. The hardness of the boride layer formed on the surface of the steel substrate was over 1500 VHN. Experimental results indicated that there is a nearly parabolic relationship between boride layer and process time for higher temperatures. Optical microscope cross-sectional observation of the borided layer revealed columnar and compact morphology. Moreover, an attempt was made to investigate possibility of predicting the hardness and depth of boride layer variation and establish some empirical relationship between process parameter of boriding and boride layer, and hardness changes using back-propagation learning algorithm in ANN. Modelling results have shown that hardness and depth of boride layer were predicted with high accuracy by ANN.

High temperature diffusion chromizing as a successful method for CVD-diamond coating of steel

Using chromium carbide intermediate layers, generated by a novel diffusion process, well adherent CVD-diamond coatings were deposited onto large surfaces of 41Cr4 steel substrates. The chromium carbide intermediate layers feature excellent barrier properties against the diffusion of iron from the substrate and against the diffusion of carbon from the gas phase during the diamond deposition. The diamond coatings show also a very good adhesion. Only at a critical load of 150 N in the scratch test is the diamond coating stripped from the substrate. The measured Raman spectra prove a high diamond quality. The thickness of the adhesive diamond coatings can be increased through a tension-reduced structuring of the substrate surface.

Mechanical behavior of borides formed on borided cold work tool steel

In this study, some mechanical properties of borided cold work low-alloy tool steels were investigated. Boronizing was performed in a solid medium consisting of Ekabor-I powders at 1000°C for 2, 4 and 6 h. The substrate used in this study was high-carbon, low-alloy tool steel essentially containing 1.18 wt.% C, 0.70 wt.% Cr, 0.30 wt.% Mn, 0.10 wt.% V and 0.25 wt.% Si. The presence of borides (FeB+Fe 2B) formed on the surface of steel substrate was confirmed by optical microscope and X-ray diffraction (XRD) analysis. The hardness of the boride layer formed on the surface of the steel substrate and unborided steel substrate were 1854 and 290 kg/mm 2, respectively. Experimental results revealed that longer boronizing time resulted in thicker boride layers. Optical microscope cross-sectional observation of the borided layers revealed denticular morphology. The fracture toughness of the boride layers measured by means of a Vickers indenter with a load of 3 N was in the range of 2.52–3.07 MPa m 1/2.

A multi-edge X-ray absorption spectroscopy study of the reactivity of zinc di-alkyl-di-thiophosphates anti-wear additives: 2. In situ studies of steel/oil interfaces

Multi-edge X-ray absorption spectroscopy, using synchrotron radiation, was used to examine changes in the structure and chemical composition of steel/oil interfaces when mediated by the presence of the anti-wear additive zinc di-alkyl-di-thiophosphate (ZDDP). The experiments were carried out at the Zn, Fe, O and C K-edges and the Zn and Fe L II/III-edges. Examination of the steel substrate, prior to reaction, revealed that the metal surface was partly oxidised, with the oxide structure mostly involving the iron atoms having a tetrahedral coordination to oxygen. Distinct changes to the oxide structure were observed following its reaction associated with the formation of its interface with ZDDP formulated in lubrication oil. Temperature programmed studies on the interfacial structure were consistent with a model involving ion exchange between Zn atoms in ZDDP and Fe(II) cations in the oxide in a reaction that appeared to be reversible below 75°C. Grazing incidence absorption spectroscopy measurements provided evidence for the breakdown of the ZDDP molecule following its adsorption onto the steel substrate surface. At higher temperatures chemical reaction between the additive and the surface oxide layer led to the formation of an amorphous anti-wear film. The structure of this film was consistent with a Zn–O bond (1.98 Å) typical of partly oxidised sulphur atoms associated with the formation of a random network glass structure with corner sharing thiophosphate and sulphate anions containing network-modifying Zn cations. A reaction scheme consistent with the proposed structure is discussed.

Characterization of borides formed on impurity-controlled chromium-based low alloy steels

Abstract This study reports on characterization of borides formed on impurity-controlled steels essentially containing 0.3% C, 0.02% P, 0.5% Cr; 0.3% C, 0.02% P, and 1.0% Cr. The formation of borides on the impurity-controlled chromium-based low alloy steel substrates was performed using thermochemical boronizing technique at 940°C for 5–7 h. The boronizing molten salt bath, in which samples were immersed, consisted of borax, boric acid, and ferro-silicon. The presence of non-oxide ceramic borides (FeB, Fe2B, CrB, Cr2B) was confirmed by the classical metallographic technique, scanning electron microscopy and X-ray diffraction analysis. A wavelength dispersion X-ray dot map showed that boron diffused into the substrate, i.e. the diffusion layer is thicker than that of the coating layer. The hardness of non-oxide ceramic borides formed on the surface of steel substrate were measured using a Vickers microhardness tester with a load of 2 N. The hardness of non-oxide ceramic borides was over 1500 HV. Depending on boronizing time, the thickness of borides ranged from 25 to 200 μm and the fracture toughness of non-oxide ceramic borides ranged between 3.42 and 4.40 MPa m1/2. It was observed that chromium has a negative role on the fracture toughness and boride layer thickness. Metallographic analysis revealed that the borides formed on the surface of steel have a columnar structure.

Plasma nitriding enhanced by hollow cathode discharge – a new method for formation of superhard nanocomposite coatings on steel surfaces

The article describes a new method of formation of superhard (⩾40 GPa) coatings on surfaces of steel substrates during their nitriding with an auxiliary cathode the surface of which is furnished with holes. The auxiliary cathode fulfills two functions: (i) it intensifies the nitriding discharge by hollow cathode discharges generated in the holes and (ii) strongly sputters the auxiliary cathode material. The sputtered material is transferred onto the surface of nitrided steel samples where it forms a new surface layer. The auxiliary cathode is made of material which contains two elements; Mo and C. This makes it possible to form superhard nanocomposite films. The superhard films are two-phase nanocomposites of the type nc-Mo 2C/(a-C+a-Mo 2N). Superhard films with hardness of about 53 GPa were prepared. The conditions under which superhard crystalline/amorphous nanocomposites can be prepared are given.

Anodic dissolution of diamondlike carbon film-coated type 301 stainless steel

The resistance of thin diamondlike carbon (DLC) films to anodic breakdown in aqueous electrolytes was investigated using voltammetry. The films were less than 0.5 μm thick and were deposited on type 301 stainless steel substrates using plasma-assisted chemical vapor deposition (PACVD) from either methane, acetylene, or 1,3-butadiene precursors with argon or hydrogen as diluent. A 10 nm thick polysilicon (PS) film was plasma-deposited prior to DLC film deposition to improve adhesion. The electrolytes used for corrosion testing were mixtures of 0.1 M NaCl and 0.1 M Na2SO4 and 0.1 M HCl and 0.1 M Na2SO4 in de-ionized water. The measured anodic current was lowest for the films deposited from butadiene and highest for those deposited from methane. The anodic current also increased with an increase in the hydrogen content in the feed gas mixture. In addition, the DLC films deposited at higher gas flow rates offered more resistance to anodic dissolution than those deposited at lower gas flow rates. Annealing improved the film performance. There appears to be an optimum DLC film thickness which provides the maximum resistance to anodic dissolution. In the best case, the DLC films reduced the anodic dissolution of bare stainless steel by about 4 orders of magnitude in the passive region. Atomic force microscopy studies of coated and uncoated stainless steel showed that the DLC films conformed to the steel substrate surface and had no effect on surface roughness, while DLC coated silicon substrates showed no evidence of pores.

Microstructure and properties of laser-clad high-temperature wear-resistant alloys

A 2-kW CO 2 laser with a powder feeder was used to produce alloy coatings with high temperature-wear resistance on the surface of steel substrates. To analyze the microstructure and microchemical composition of the laser-clad layers, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray microanalysis system was employed. X-ray diffraction techniques were applied to characterize the phases formed during the cladding process. The results show that the microstructure of the cladding alloy consists mainly of many dispersed particles (W 2C, (W,Ti)C 1− x , WC), a lamellar eutectic carbide M 12C, and an (f.c.c) matrix. Hardness tested at room and high temperature showed that the laser-clad zone has a moderate room temperature hardness and relatively higher elevated temperature hardness. The application of the laser-clad layer to a hot tool was very successful, and its operational life span was prolonged 1 to 4 times.

Hardness improvement of TiC-reinforced ferrous surface composites fabricated by high-energy electron beam irradiation

Metal matrix composites in general have excellent performance compared with metallic materials because of the ductile fracture behavior in addition to high strength and elastic modulus. Particularly, TiC-reinforced ferrous composites have highly stabilized TiC particles inside the matrix, and thus can be applied to structures requiring resistance to abrasion and corrosion and high-temperature properties. They are typically fabricated by powder metallurgy route, casting, liquid phase sintering, self-sustaining high-temperature synthesis, plasma spraying, and surface alloying using laser, but these methods usually demand complex processes to achieve homogeneous distribution of TiC particles. Recently, an attempt has been made in direct irradiation with high-energy electron beam in order to achieve surface hardening or surface alloying. In this study, a simple process was presented to fabricate a TiC-reinforced ferrous surface composite with enhanced surface hardness by depositing TiC powders on the surface of a plain carbon steel substrate and then irradiating high-energy electron beam.

Plasma catalytic reaction in ammonia synthesis in the microwave discharge

Practically, ammonia is made in the Haber process, in which the synthesis is carried out on promoted iron catalyst at higher pressures and temperatures, In the plasma process, NH radicals were formed in the nitrogen-hydrogen plasma and the NH radicals would be quenched by hydrogen molecules to form ammonia. When the catalyst was placed in the plasma, synergistic effects of plasmas and catalysts on the ammonia synthesis were observed. The species in the ECR plasma do not collid in the plasma and the ammonia formation reaction would proceed only on the surface of the catalyst. Thus the reaction occurred in the ECR plasma apparatus was investigated from both the identifications of species in the plasma and adsorbed species on the surface of steel substrate placed in the plasma to clarify the reaction scheme of the ammonia synthesis. A dissociative adsorption of excited nitrogen molecules and molecular ions or a direct adsorption of NH radicals on the surface of the catalyst would promote the formation reaction of ammonia.

The effect of the sputter cleaning of steel substrates with neutral molecule source on the adhesion of TiN films

The effect of sputtering the surface of a high-speed steel substrate with a neutral molecule source, after alkaline cleaning and boiling water dip-drying, on the adhesion of Arc-PVD TiN coatings was studied. For comparison, the effects of several drying techniques on the adhesion of TiN coatings were also investigated. These samples were all similarly cleaned in alkali but were dried with different techniques such as boiling water dipping, alcohol and hot trichloroethylene dipping. Before coating all the samples were heated and sputter-cleaned with Ti ions. Coatings were all 1.6–1.9 μm thick with hardnesses varying between 34 and 37 kN mm −2. Adhesion was tested with a scratch tester. Surfaces sputtered with neutral molecules exhibited much higher adhesion than surfaces dried with other techniques and cleaned by Ti ions.

溶射皮膜の摩擦特性と高力ボルト摩擦接合部への応用

The sliding friction between solids is a problem related to the material surface and its neighborhood. It is very important to control and adjust it in engineering. In this research, the characteristics of sliding friction between thermal sprayed surfaces have been studied. Materials sprayed were aluminum (Al), zinc-5% aluminum alloy (Zn-A1), and alumina (Al2O3) and sliding pairs were either of the same material or of different materials. Further, it also has been studied from the standpoint of applying thermal spraying to the surface treatment for high-strength bolted joints. In the experiments, frictional force was recorded as a function of sliding distance. It was found that force-distance curves of as-coated specimens could be classified into two types; one is periodical oscillation with the stick-slip such as for the sliding pair of Zn-Al/Zn-Al and the other is with random fluctuation for the sliding pairs of Al/Al and Al2O3/Al2O3. The coefficient of friction was biggest for sliding pair of Al/Al, which is about 2 times as high as that of the shot-blasted surface of mild steel substrate (for Al/Al and Zn-Al/Zn-Al). It has been confirmed also that Amontons law is applicable in any of the sprayed sliding pairs tested. Especially, it has be shown that aluminum-sprayed coating and zinc-sprayed coating will be expected to apply to high-strength bolted joints, because of having big coefficient of friction and strong corrosion resistivity.

Reaction scheme of ammonia synthesis in the ECR plasmas

The reaction scheme of ammonia synthesis in the ECR plasma apparatus teas investigated from both identifications of the species in the plasmas and the adsorbed species on the surface of a steel substrate placed in the plasmas. The adsorbed species were considerably different when different kinds of plasmas are used. NH, species were adsorbed on the steel substrate surface in the nitrogen-hydrogen plasma, and N2 molecules were adsorbed in the nitrogen plasma. By the application of a negative bias potential on the substrate, the adsorption of N atom or Fe-N bond formation was identified on the steel substrate surface. When the stainless steel wall of the chamber was covered with aluminum foil, the yield of NH,, radicals, which were on both the substrate and in the plasma, decreased. By exposure of the substrate, on which N2 molecules or N atoms adsorbed, to the hydrogen plasma, N2 and N disappeared from the steel substrate surface, forming ammonia. Moreover, the adsorption of NH,, radicals disappeared when the stainless steel wall surface was covered with aluminum foil. Thus, the surface of the stainless steel wall acts as a catalyst in ammonia formation. The formation of ammonia in the nitrogen-hydrogen ECR plasma, in which the steel substrate served as the catalyst, is not only through the dissociative adsorption of excited nitrogen molecules but also through the dissociative adsorption of nitrogen molecular ions.

A transmission electron microscopy examination of the interface between osteoblasts and metal biomaterials

Transmission electron microscopy was used to examine the interface between metal implant materials and bone cells. Specifically, neonatal rat calvaria osteoblasts were cultured on CoCrMo alloy and on 316L stainless steel discs (mechanically polished to a 0.3 micron finish) in Dulbecco's Modified Eagle Medium (supplemented with 10% fetal bovine serum, 50 micrograms/mL ascorbic acid, and 10 mM beta-glycerophosphate) under standard, sterile, cell culture conditions for 14 to 28 days. At the end of the prescribed time periods, the cells were fixed and embedded in resin before removing the metal substrates using an electrolytic dissolution technique and a 7% NaCl solution. Transmission electron microscopic examination of stained, ultrathin sections of the biological samples revealed an intact interface with microscopic details characteristic to the cell line and similar to those reported in the literature for animal and explant studies. The osteoblasts exhibited continuous contact and intimate apposition to both the CoCrMo and stainless steel substrate surfaces and grew in multilayered structures; an electron dense layer (composed of mucopolysaccharides and proteins) was observed at the surface of both substrates; collagen fibrils and mineralized foci were observed in the extracellular matrix interspersed among the multilayered osteoblasts.

Mechanical Properties of Particulate MMC/AISI 304 Friction Joints.

The influence of joining parameters (rotational speed, frictional time and pressure) on the notched tensile strength of dissimilar MMC/AISI 304 stainless steel friction joints is investigated. Frictional pressure and rotational speed have a statistically-significant effect on notched tensile strength values. The highest notched tensile strength properties occur in joints produced using a high frictional pressure (120 MPa) since extremely thin transition regions are produced at the joint interface and the area fraction of joint interface fracture in broken notched tensile test specimens is negligible.The average particle diameter and inter-particle spacing decrease markedly in the region immediately adjacent to the bondline. It is suggested that the decrease in particle dimensions results from the combined effects of non-uniform plastic straining during friction welding and due to thermal shock and impaction of alumina particles on the contacting surface of the stainless steel substrate.

電子シャワー法によるステンレス基板への銅の高密着性膜

Copper-coated stainless steel is used in switches requiring a strong film in adhesion. The adhesion of the film prepared by electron shower was at least 100 times higher than that prepared by conventional thermal vapor deposition. To obtain a film with a high adhesion, we irradiated an electron shower on the substrate before evaporating the copper, which enhanced the formation of chromium oxide on the surface of the stainless steel substrate. The highly adhesive copper film was to form copper oxide with the oxygen atoms of the chromium oxide, but the thermal diffusion effect on adhesion was low, because thermal diffusion of copper was suppressed by chromium oxide. When the substrate was contaminated by carbon and chromium carbide formed instead of chromium oxide, no adhesive film could be formed, even with the use of the electron shower.

New high-resolution electrostatic electron spectrometer for conversion electron Mössbauer spectroscopy

The construction and performance of a new electron spectrometer using an electrostatic 90°-spherical deflection analyzer (SDA) is described. The spectrometer is suited for depth-selective conversion-electron Mossbauer spectroscopy (DCEMS) on surfaces and thin films in ultra-high vacuum (UHV) at temperatures ranging between 40–1000K using K- and L-conversion electrons of57Fe. The spectrometer is designed for 2% electron-energy resolution and about 5% (of 4π) transmission for 7.3 keV K-conversion electrons of57Fe. The energy resolution has been confirmed experimentally. We demonstrate that DCEMS in general and our instrument in particular are capable of detecting a thin (∼50 Fe A) Mossbauer-inert buried oxide layer located at the surface of a stainless steel substrate and covered by an Fe/Cr bilayer.