Surface Of Steel Substrate Research Articles

Vitreous Enamel Coating on Steel Substrates

Vitreous enamel is a glassy coating formed on a metal substrate by firing at temperatures above 800 °C. The quality of vitreous enamel coating depends on the pre-treatment of the steel substrate surface and the quality of enamel slip. The main aim of this study was to characterize the composition of the steel substrate surface after firing with double finish, to explain the effect of steel substrate surface pre-treatment (blasting, acid pickling) on forming the phase interface of the steel substrate – vitreous coating system, and on its final microhardness, fracture strength and the adhesive properties of the coating. To achieve these aims, the following experimental methods were used: Mössbauer spectroscopy, X-ray diffraction, electron analyzer, and EDAX. Based on the chemical composition of the initial enamel slip and the firing technology, the metal - enamel system interface exhibited various ratios of layers of magnetite, hematite, nonstoichiometric wüstite, and crystals of faylite. The measuring results indicate that the quality and age of enamel slip influences the brittle fracture properties of vitreous enamel coating.

Thermomechanical analysis and modeling of the extrusion coating process

AbstractDuring the extrusion coating process, a polymer film is extruded through a flat die, stretched in air, and then coated on a substrate (steel sheet in our case) in a laminator consisting of a chill roll and a flexible pressure roll. The nip, i.e. the area formed by the contact between the pressure and the chill rolls, constitutes the heart of the extrusion coating process. Indeed, in this region, some of the most critical properties, such as adhesion, barrier properties, optical properties, are achieved or lost. In this article, we first present an experimental investigation of the coating step, which enables to characterize the leading thermomechanical phenomena. It is shown that there is no polymer macroscopic flow in the nip, but a local flow within the asperities of the steel substrate surface. This microscopic flow, at the interface between the film and the substrate, is slowed by strong cooling conditions in the nip. Several models are then proposed, giving access to the temperature profile through polymer thickness and substrate, the pressure distribution in the nip as well as the behavior of the polymer melt in the nip at the interface with the substrate. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Production of LaPO4 coatings using a novel ultrasonically-assisted plating technique

Abstract Dense LaPO4 and LaPO4–Al2O3 coating films were produced on the surface of stainless steel substrates at room temperature and ambient pressure with the aid of a novel ultrasonic-based mechanical coating method, which we call UMCA. The main emphasis was on examining the conditions necessary for the successful coating operation and characterizing the as-deposited coatings for the thickness, uniformity and surface morphology. The experimental results suggested that hardness and thermal conductivity of balls and substrate are key parameters influencing the coating efficiency. The coated samples showed an improved hot corrosion resistant in Na2SO4–NaCl molten salts at 950 °C.

Study in the effect of annealing on hydrogen retention properties of C‐90%SiC films

AbstractCarbon‐rich silicon carbide (C‐90%SiC) films as hydrogen barriers were deposited on the surface of stainless steel substrates with magnetron sputtering, and then bombarded by argon ion beam. In order to remove the argon atoms reserved during films preparation, some samples with the prepared C‐90%SiC films were thermally annealed for 30 min at 473, 673 and 873 K in vacuum, respectively. These samples together with the un‐annealed ones were then irradiated by a 5 keV hydrogen ion beam. SEM was used to investigate the surface micrograph of those films and SIMS was used to measure the mass spectra of positive species and the depth distribution of argon and hydrogen in the samples. A remarkable decrease in hydrogen intensity in the substrates with annealing indicates that annealing for removing argon can effectively improve hydrogen retention properties of the C‐90%SiC films. Copyright © 2008 John Wiley & Sons, Ltd.

An experimental study on synthesizing submicron MoSi 2-based coatings using electrothermal explosion ultra-high speed spraying method

The MoSi 2-based coatings were synthesized on the surface of the low carbon steel substrate using electrothermal explosion ultra-high speed spraying method. Microstructure, phase structure, elements distribution and microhardness of the coatings were characterized by SEM, XRD, EDS and Vickers hardness tester, respectively. It is found that MoSi 2 coating and MoSi 2 + MoB 2 multiphase coating were in-situ formed. The coatings have compact microstructure, submicron-grain and high hardness. The bonding of coating-substrate is metallurgical one. The hardness and microstructure of the MoSi 2 coating were improved by boron alloying. The average and highest hardness of the MoSi 2 coating are 1340 HV 0.2 and 1390 HV 0.2, respectively, and that of MoSi 2 + MoB 2 multiphase coating are 1650 HV 0.2 and 1785 HV 0.2, respectively.

Studies on compositionally graded silicon carbide dispersed composite surface on mild steel developed by laser surface cladding

In the present study, an attempt has been made to develop a compositionally graded SiC dispersed phase on the surface of mild steel substrate by two steps laser surface cladding technique, with a top layer having 85% Fe + 15% SiC and bottom layer of 95% Fe + 5% SiC. Laser surface cladding was conducted using a continuous wave CO 2 laser, and simultaneous feeding of a mixture of Fe and SiC (in the above mentioned ratio) with Ar as shrouding atmosphere. The microstructure of the composite layer consisted of dispersion of SiC particles in the matrix of ferrite and iron silicide (Fe 2Si). In the clad layer, SiC particles were found to be partially dissociated and the degree of dissociation was higher at the bottom layer as compared to the top layer. Area fraction of particles was found to be maximum at the surface and decreased with depth. The microhardness of the surface was improved to a maximum of 600 VHN (at the surface) as compared to 190 VHN of mild steel substrate and decreased gradually with depth. A significant improvement in wear and corrosion resistance on the clad surface was observed.

Effect of Substrate Temperature on Deposition Behavior of Copper Particles on Substrate Surfaces in the Cold Spray Process

The deposition behavior of sprayed individual metallic particles on the substrate surface in the cold spray process was fundamentally investigated. As a preliminary experiment, pure copper (Cu) particles were sprayed on mirror-polished stainless steel and aluminum (Al) alloy substrate surfaces. Process parameters that changed systematically were particle diameter, working gas, gas pressure, gas temperature, and substrate temperature, and the effect of these parameters on the flattening or adhesive behavior of an individual particle was precisely investigated. Deposition ratio on the substrate surface was also evaluated using these parameters. From the results obtained, it was quite noticeable that the higher substrate temperature brought about a higher deposition rate of Cu particles, even under the condition where particles were kept at room temperature. This tendency was promoted more effectively using helium instead of air or nitrogen as a working gas. Both higher velocity and temperature of the particles sprayed are the necessary conditions for the higher deposition ratio in the cold spraying. However, instead of particle heating, substrate heating may bring about the equivalent effect for particle deposition.

SEM study of defects in PVD hard coatings

Hard coating defects are produced by foreign particle contamination on substrate surface before and during coating, or due to arcing. In this work, CrN, TiAlN and CrN/TiAlN multilayer hard coatings were prepared by thermoionic arc ion plating deposition system BAI 730 (Balzers) and by sputter deposition in CC800 (CemeCon). We investigated the concentration of defects, its size and structure after tool steel substrate surface pretreatment (polishing, ion etching) as well as after deposition by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM).

Development of nano-structured Al2O3-TiB2-TiN coatings by combined SHS and laser surface alloying

A powder mixture of aluminium (Al), titania (TiO2) and hexa-boron nitride (h-BN) was laser-triggered to undergo SHS (self-propagating high temperature synthesis) and was subsequently laser alloyed onto a mild steel substrate surface. A nano-structured coating was formed with high microhardness (∼3000 HV0.05 at the cross-section and ∼2600 HV0.2 on the top surface). X-ray diffraction (XRD) identified the presence of aluminium oxide (Al2O3), titanium di-boride (TiB2), titanium nitride (TiN), iron (Fe) and its borides (FeB, Fe2B) in the coating. Scanning electron microscopy (SEM) and high resolution transmission electron microscopic (HRTEM) analysis of the coating revealed nano-fibrous titanium-rich reinforcements in a matrix of nano-crystalline alumina. The thickness of titanium di-boride nano-fibres was an order of magnitude higher than the size of nano-alumina crystallites.

Direct Growth of Aligned Multiwalled Carbon Nanotubes on Treated Stainless Steel Substrates

Growth of aligned carbon nanotubes (CNTs) on electrically conductive substrates is promising for many applications; however, the lack of complete understanding of the substrate effects on CNT growth poses a lot of technical challenges. Here, we report the direct growth of aligned multiwalled nanotubes (MWNTs) on chemically treated stainless steel (Type 304) using a chemical vapor deposition (CVD) process. A detailed X-ray photoelectron spectroscopy (XPS) analysis has been carried out for the various treated samples in order to better understand the correlation between the surface properties of the substrates and the MWNT growth. The XPS studies revealed that the CNTs prefer to grow on the enriched surface of iron oxides obtained by the chemical treatment rather than on the passive chromium oxide films present on the surface of the as-received stainless steel substrates. The density and alignment of the MWNTs could therefore be controlled by tuning the ratio of the iron oxides to chromium oxides through the chemical treatment on the stainless steel surfaces. On the basis of this method, selective growth of CNT patterns on stainless steel has also been demonstrated.

Effect of a laser pre-quenched steel substrate surface on the crack driving force in a coating–steel substrate system

A mechanical model of a coating/laser pre-quenched steel substrate specimen with a crack oriented perpendicular to the interface between the coating and the hardened layer is developed to quantify the effects of the residual stress and hardness gradient on the crack driving force in terms of the J-integral. It is assumed that the crack tip is in the middle of the hardened layer of the pre-quenched steel substrate. Using a composite double cantilever beam model, analytical solutions can be derived, and these can be used to quantify the effects of the residual stress and the hardness gradient resulting from the pre-quenched steel substrate surface on the crack driving force. A numerical example is presented to investigate how the residual compressive stress, the coefficient linking microhardness and yield strength and the Young’s modulus ratio of the hardened layer to the coating influence the crack driving force for a given crack length.

Characterization of boriding of 0.3% C, 0.02% P plain carbon steel

In the present study, some mechanical properties of borides formed on the impurity-controlled plain carbon steel essentially containing 0.3% C, 0.02% P in weight was investigated. The formation of borides on the concerned steel was performed in a bath having borax, boric acid and ferro-silicon at 940 °C for various length of time between 1/2 and 10 h. Optical and scanning electron microscope (SEM) studies revealed that borides formed on the surface of steel substrate have columnar morphology. The hardness of borides is higher than 1500 DPN. The presence of borides (FeB and Fe 2B) was confirmed by X-ray diffraction (XRD) analysis.

Fabrication and adhesive properties of thin organosilane films coated on low carbon steel substrates

We investigated the fabrication and adhesive properties of thin organosilane films coated on the surface of low carbon steel substrates by curing γ-glycidoxypropyltrimethoxysilane (γ-GPS) solutions hydrolyzed in different solvents. This method appears to be a promising alternative treatment for the chromium and phosphate mainly due to its excellent corrosion protection and adhesion properties to organic coatings and a non-toxic pretreatment. In this work the elemental distribution in γ-GPS films coated on low carbon steel substrates was analyzed by an energy dispersive X-ray spectrometer (EDX), and the effect of curing temperature and solution concentration on the chemical structures of this silane was also carried out with reflection–absorption infrared (RAIR) spectroscopy. We systematically investigated the processing variables regarding adhesive strength of the film, including hydrolysis solvents, hydrolysis time, solution concentration and curing temperature. Compared with other experimental conditions, the present results provided a consistent demonstration that γ-GPS films exhibited improved adhesive strength to metal substrates in case of using DI water/methanol mixture as hydrolysis solvent, hydrolysis time of 48 h, solution concentration of 10%, curing temperature of 150 °C and curing time of 1 h. The fracture mode of γ-GPS films varied with different deposition parameters.

Deposition of carbon nanofibers on a low carbon steel substrate using an oxy-acetylene reducing flame

Carbon nanofiber (CNF) coatings were successfully deposited on a low carbon steel substrate that was pretreated by con-centrated nitric acid using an oxy-acetylene reducing flame. The morphologies and the microstructures of the CNF coatings were char-acterized using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The CNFs were compact, entangled with each other, and highly graphitized with diameters from 80 to 100 nm and lengths from 3 to 5 μm. They tended peel off the substrate because of weak adhesion strength. Iron oxide particles were produced on the pretreated low carbon steel substrate surface in the flame, and these acted as growth catalysts for the CNFs.

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.

Examination of Substrate Surface Melting-Induced Splashing During Splat Formation in Plasma Spraying

Impacting of a molten droplet with a melting point much higher than the substrate results in melting of the substrate around the impact area. Melting of the substrate surface to a certain depth alters the flow direction of the droplet. The significant change of fluid flow direction leads to the detaching of fluid from the substrate. Consequently, splashing occurs during the droplet-spreading process. In the current study, molybdenum (Mo) splats were formed on a stainless steel substrate under different plasma-spraying conditions. For comparison, Mo splats were also deposited on an Mo surface. The substrate surface was polished prior to deposition. The powders used had a narrow particle size distribution. The results show that the morphology of splats depends significantly on the thermal interaction between the molten particle and the substrate. The splat observed was only a central part of an ideal disk-like complete splat. The typical pattern of Mo splats was of the split type, presenting a small split structure on the surface of the stainless steel substrate. With Mo particles, the preheating of a steel substrate has no effect on splat morphology. On the other hand, a disk-like Mo splat with a reduced diameter of a dimple-like structure at the central area of the splat was formed on Mo substrates, and splashing can be suppressed through substrate preheating. Based on the experimental results, a surface melting-induced splashing model was proposed to explain the formation mechanism of the Mo splat on a steel surface. The influence of droplet condition on splat formation is discussed.

Fabrication, characterization and photocatalytic activity of preferentially oriented TiO 2 films

Preferentially oriented anatase TiO 2 films were uniformly deposited on the surface of stainless steel substrate by a liquid phase deposition (LPD) method at 60 °C using TiF 4 and H 3BO 3 as precursors. The as-prepared TiO 2 films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The photocatalytic activity of the as-prepared TiO 2 films was evaluated by the photocatalytic oxidation of NO in the gaseous phase. It was found that the deposition conditions, such as the precursor concentrations (H 3BO 3 and TiF 4), the deposition time and the pH, had an obvious effect on the formation of oriented TiO 2 films. The prepared TiO 2 films showed a preferential orientation in the [0 0 1] direction perpendicular to the stainless steel substrate. A formation mechanism was proposed to account for the preferential orientation and textured morphology of the TiO 2 films. The photocatalytic oxidation of NO indicated that the preferentially oriented TiO 2 films exhibited an obvious photocatalytic activity without high-temperature calcination.

Study on Mechanical Properties of Cermet Materials Fabricated from Ternary Boride Cladding on Both Sides Surface of Steel Substrate

Using Mo powder, B-Fe alloy powder and Fe powder as raw materials, with proper forming additives, the slurry was prepared. The green body was formed by spray method on both sides of 16Mn and Q235 steel substrate separately. Both side ternary boride based cermet cladding materials FC-V16Mn and FC-VCuQ235 were fabricated by liquid phase sintering technology. Both materials have high hardness, bending strength and good corrosion resistance.

Tribological properties of oxidised boride coatings grown on AISI 4140 steel

In this study, we investigated the wear behaviour of borided and borided + short-duration oxidized AISI 4140 steel. Boronizing was carried out in a slurry salt bath consisting of borax, boric acid and ferro silicon. Also, short-duration oxidizing treatment was applied to borided steel to produce glass-like boron oxide layer. The short-duration oxidizing was performed at 750 °C for 3 min. Optical and scanning electron microscope (SEM) cross-sectional examinations of borided layer revealed a needle-shaped morphology. The presence of non-oxide boride type ceramics FeB and Fe 2B formed on the surface of steel substrate was confirmed by classical metallographic technique and X-ray diffraction (XRD) analysis. The hardness of borides formed on the surface of steel substrate and unborided steel substrate were 1446–1690 HV 0.1 and 280 HV 0.1, respectively. The wear behaviour of borided steel were characterised by using a pin-on-disc technique. The borided and short-duration oxidized steels, in the form of pins were allowed to slide against a hard AISI 440C stainless steel disc (63 HRc). The sliding velocity of 1 m s − 1 for borided and short-duration oxidized steel and the nominal load on the pin was 20 N. The highest wear rates were observed on disc slide against the base steel, whilst the lowest wear rates occurred during sliding against the borided and short-duration oxidized steel surfaces. It was observed that the friction coefficient of unborided (hardened + tempered) and borided steels ranged from 0.50 to 0.60, but after short-duration oxidizing, the friction coefficient of borided steel was dropped to 0.12.