Papers by Keyword: Thermal Spray

Abstract: This paper presents a comparative study on the corrosion behaviour of the Al depositions, obtained by thermal spraying in electric arc - the classic method (ASP) and the Al deposits behaviour, carried out with a thermal spray combined device (CTSD). The use of CTSD allows the thermal field modification of the spraying jet and implicitly the modifying the mechanical, physical and chemical properties of the deposits of aluminium. Evaluation of the corrosion behaviour of the aluminium deposits was achieved by exposure to salt water - sea water (3.5NaCl). The corrosion products, formed on the surface of the coatings, were investigated based on the photographic records, electronic microscopy – SEM and X-ray diffraction. The aluminium oxide, obtained on the depositions, carried out by using CTSD - exposed in saline environment is more adherent then the oxide obtained on the deposits, carried out through ASP - which leads to a loss in thickness.

Abstract: In this work, the thermal spraying sacrificial anode was investigated as reinforced concrete structure cathodic protection method. During our experiment, the performance of the thermal spraying sacrificial anode was studied using electrochemical method, metallographic microscopy method and simulation tests. And the results show that the thermal spraying sacrificial anodes are better than traditional sacrificial anodes. The method of thermal spraying applied in sacrificial anode field is successful, which solve the problem of insufficient driving initial potential of traditional sacrificial anode in the concrete structure.

Abstract: Titanium (Ti) and its alloys are widely used in medical applications due to its superior mechanical properties and biocompatibility. Hydroxyapatite (HA), due to its similarity with teeth and bone material, is also widely used in clinical applications and orthopaedic implant manufacture. In this study, composite powers containing titanium with different wt % of HA were coated on stainless steel substrate using high velocity oxy-fuel (HVOF) spray technique. These Ti+HA coatings were characterized using XRD technique to indentify phases present in the coating. Small amount of oxide phases were identified apart from the original Ti and HA in the coatings during XRD analysis. The microstructure analysis of the coating surface using FESEM and EDX revealed dense and homogeneous coatings along with few well distributed pores.

Abstract: The indentation methods (HR15N, HV0.3, HIT, EIT) were used to evaluate differences between the WC-based coatings with 12, 17 and 25% of Co binder. The two sets of WC-12%Co coatings with two different sets of parameters were sprayed to evaluate the influence of spraying parameters. The measured mechanical characteristic were correlated to the to the wear resistance of the coatings evaluated by dry sand/rubber wheel test according to ASTM G-65 and pin-on disc according to ASTM G-99. The measured results showed that there is almost no difference between the abrasive wear resistance of WC-Co coating with 12 and 17% of Co binder, while the wear of coating with 25% of Co binder is significantly higher. The importance of the spraying parameters on the WC-12%Co coatings properties has been found to be comparable to the importance of binder content influence.

Abstract: Steel depositsobtained by thermal spray arc have physical-chemical and mechanical properties dependent on operational parameters of the spraying process. Thus, the electric current intensity, the spray distance, the velocity, respectively the driving gas pressure are the parameters that influence the mechanical properties of the steel deposits obtained by thermal spraying. The interaction between particles- gas drive seen in the classic arc spray has the effect the lowering of particles temperature and implicitly of the physical and mechanical properties of the deposit. Using a new device, combined, in which over the thermal field, created by the electric arc, would overlap a second thermal field, created by a gaseous fuel burning, would determine the maintaining of high temperature of the particles and implicitly changes of the physical, chemical and mechanical properties of the deposit. Such a combined spraying device would be called device for spraying in electric arc-thermally activated. The paper aims to present a comparative study of the physic chemical and mechanical properties of steel deposits obtained with two spraying processes: the classical process and the combined spraying process - in electric arc thermally activated.Investigations carried out on the structure of deposits by electron microscopy SEM, XRD analysis and image analysis performed at zone level Layer-Substrate as well the deposits adherence assessment in accordance with EN 582-allows the highlighting properties, the arguing of differences between the properties of the deposits made by the two methods as well as the establishing advantages and disadvantages using those processes.

Abstract: The present works concerns in developing alternative interconnect material for solid oxide fuel cell (SOFC) application. For this purpose, ferritic stainless steel is used as the substrate material while various nickel composite layers were coated on the substrate in order to improve its oxidation resistance at SOFC application temperature. Nickel layers were deposited on ferritic stainless steel by high velocity oxy-fuel (HVOF) method. In order to create nickel-oxide layer, the coated samples is then heated at temperature of 950°C for 1 hour, wherease sol-gel coating was performed on the coated samples in order to create nickel manganese oxide spinnel composite layers. All samples were then oxidized at temperature 800°C for 8 hours, in order to evaluate their oxidation characteristics at SOFC service temperature. Before and after oxidation, x-ray diffraction (XRD) and scanning electron microscope (SEM) were performed to all samples. It was observed that coated samples effectively inhibit the formation of chromium oxide that normally occurs on stainless steel surface at SOFC service temperature.

Abstract: Cobalt based oxide are promising as coating material for solid oxide fuel cell interconnect due to their high oxidation resistance and conductivity. In this report, Co-based coating layer was deposited on AISI 430 ferritic stainless steel substrate using thermal spray methods. The high temperature oxidation behavior of Co-based coating was studied in air atmosphere at 800 °C. Optical and SEM observation shows that the total thickness of Co-based layer was about 100-120 μm. The coatings were mainly growth by the melted particles impacting on the substrate that flatten to form splats which later on piled on top of the others. Phase identification by XRD showed that the coating layer contained Co₃O₄, and NiO oxides. EDS analysis indicated that the coating layer were sufficient to prevents the formation and the growth of Cr₂O₃ scale. The Co-based coating shows relatively a large mass gain during oxidation compared to the uncoated steel, with parabolic rate constant, K_p = 4x10^-15 gr².mm^-4.ks^-1.

Abstract: Many surface protection methods have been developed to apply to constructional steels to be used under severe corrosive environments. Thermal spray coating has been known to be an attractive technique due to its relatively high coating speed. However, the high corrosion resistance of coating films deposited by thermal spray method is increasingly required to expand its application. Four types of coated films (DFT: 200um), that is, pure zinc, pure aluminum, and two Al-Zn alloy (Al:Zn=85:15 and Al:Zn=95:5), were coated onto carbon steel (SS401) with arc spraying, and the corrosion behavior of their samples were evaluated by the electrochemical method in this study. The pure aluminum sample had the best corrosion resistance when exposed to seawater solution and alloy (Al:Zn=85:15), so called galvalume and alloy (Al:Zn=95:5) samples followed the pure aluminum sample. The pure zinc sample ranked 4^th in corrosion resistance in this study. Morphology of corroded surfaces of pure aluminum and alloy (Al:Zn=85:15) samples exhibited a general corrosion pattern, however, the patterns of intergranular and pitting corrosion were observed for the pure zinc and alloy (Al:Zn=95:5) samples respectively. Pure zinc sample had the smallest value of porosity ratio compared to other samples due to its heavier density. Keywords : Surface protection methods, Thermal spray, Corrosion resistance, Pure aluminum, Pure zinc, Porosity ratio

Abstract: Rotating bending fatigue tests had been performed using A5052 aluminum (Al) alloy with the hybrid coatings which consisted of tungsten carbide including 12% cobalt (WC-12Co) interlayer and diamond-like carbon (DLC) film, in order to investigate the effect of hybrid coating on the fatigue behavior. The WC-12Co layer was thermally sprayed by a high velocity oxygen fuel (HVOF) method on A5052 with the thickness of 70, 120 or 170μm. Subsequently, the DLC film was deposited with the thickness of 15μm. The fatigue strengths of the specimens with WC-12Co single layer were higher than those of the substrate and increased with increasing the thickness of WC-12Co layer. The fatigue strengths of the specimens with the hybrid coating of 70μm WC-12Co interlayer and 15μm DLC film were better than those of the specimen with 70μm WC-12Co single layer. Thus the hybrid coating structure was effective to improve fatigue strengths. However the beneficial effect of hybrid coating was not apparent in the specimens with thicker WC-12Co interlayer of 120 and 170μm.

Abstract: Thermal spray technology allows providing wear-resistant coating on the surface of mechanical components. In this study, wear characteristics of thermally sprayed Al/SiC composite coatings were evaluated. These Al/SiC composite coatings reinforced with SiC particles were fabricated on Al 6061 substrate by thermal spray process. Dry sliding wear tests were performed using the varied sliding speeds and applied loads. Wear behavior of these Al/SiC composite coatings were investigated using scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDX) and X-ray diffraction(XRD).