Papers by Keyword: Thermal Spray

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Authors: W.T. Hsiao, W.H. Liao, M.S. Leu, Cherng Yuh Su
Abstract: The image of thermal spray splats is difficult to collect due to its high velocity of droplets. Especial in High Velocity Oxy-Fuel (HVOF) process, the process present higher velocity of flame jet correlated to other thermal spray process. The system presents at this article describes a useful splats catching method to obtaining splats during thermal spray deposited. Capabilities and advantages of using this instrument are declared at this theme. The final result presented the instrument caught the single spot of HVOF sprayed splats at sub-micro second. Splats of spot were dispersed well on the glass substrate at the obtaining system, and presented various information of droplets impact at different location on the substrate.
Authors: Ya Ping Wang
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.
Authors: M. Jeandin, F. Borit, N. Fabrègue, G. Rolland, F. Delloro
Abstract: “Art is everywhere” to quote Ben, a renowned French contemporary artist. However, there are some areas in which art is more prevalent. Thermal spray is one of them, as this presentation seeks to demonstrate. For this, each of the arts (according to their official classification) is shown to correspond to a specific key point of the thermal spray process for coating: e.g., coating build-up, additive manufacturing, deposition onto brittle and/or temperature sensitive materials (glass, wood, fabrics, polymers), powder optimization, and adhesion. Both modeling and experimental aspects are discussed, focusing on the study of particle-to-particle or particle-to-substrate interfaces, shock phenomena and advanced investigation techniques such as X-ray microtomography or high-speed instrumentation. Plasma spray and cold spray provide the relevant examples that this contribution elaborates. They relate to different industrial sectors such as aircraft-aerospace, luxury, biomedical and the automotive industry. Beyond anecdotal evidence, the discussion aims to show that an artistic approach to thermal spray does help to understand better this powerful coating process.
Authors: Gheorghe Matache, Alexandru Paraschiv, Cristian Puscasu
Abstract: The wear behaviour of thick molybdenum coatings deposited by electric arc thermal spray on steel support was investigated by micro-abrasion, a relatively recent introduced method for small scale wear testing. The wear mechanisms and wear rates without coatings penetration were investigated with respect of time corresponding to primary and secondary wear stages. The micro-abrasion of Mo coatings using SiC abrasive slurry have been discussed and wear scar characteristics were evaluated based on the experimentally results. The worn surfaces of the tested specimen were examined by SEM and the specific wear rate was calculated from experimental data. For the testing durations used it was identified the change from grooving to rolling wear corresponding to the transition of wear mode from two-body to three body-abrasion.
Authors: Niraj Bala, Harpreet Singh, S. Prakash
Abstract: The Cold spray or cold gas dynamic spraying is the new progressive step in the direction of development of high kinetic energy coating processes. The cold spray is a method for coating substrates under atmospheric conditions. In this process micron sized solid particles are accelerated and transported to substrates by means of supersonic free jets. Upon impacting the substrates, particles stick to the surface and form coatings which possess very low porosity. The paper outlines the principles involved in cold spray method and the equipment used for the technique. The cold spray method is related to classical thermal spray methods but it has some interesting additional features, which has been discussed in the paper. A fundamental feature of cold spray method i.e. concept of critical velocity along with the plausible mechanism theory responsible for the deposition of coating has been discussed briefly. Successful applications of cold spray process and its environment friendly aspect has been elaborated. It is reported that well founded cold spray technology will be able to compete for a good market share of VPS/PVD coatings in various fields like power, electronic/electrical, biotechnology, turbines and other industries. The cold spray process is still primarily in the research and development stage and only now becoming commercially available, and has been accepted as a new and novel thermal spray technique mainly in developed countries. The technology has great potential for future research especially with reference to its application to real industrial solution.
Authors: Nadimul Haque Faisal, John A. Steel, Rehan Ahmed, R.L. Reuben, G. Heaton, Bryan Allcock
Abstract: This research aims to characterise and quantify the acoustic emission (AE) generated during the high velocity oxy-fuel (HVOF) thermal spraying process, recorded using piezoelectric AE sensors. The HVOF process is very complex involving high temperature turbulent flow through a nozzle with entrained particles, the projection of these particles, and their interaction with the target surface. Process parameters such as gun speed, oxy-fuel pressure and powder specification affect various characteristics of the coating, including thermal residual stresses; the lamellar microstructure and the topology and geometry of pores, all formed when the fused powder hits the surface, forming “splats”. It is widely acknowledged in the thermal spray industry that existing quality control techniques and testing techniques need to be improved. New techniques which help to understand the effects of coating process parameters on the characteristics of the coating are therefore of value, and it was anticipated that recording the AE produced when the fused particles contact the surface would aid this understanding. As a first stage, we demonstrated here that AE associated with particle impact can, in fact, be discerned in the face of the considerable airborne and structure-borne noise. In order to do this, a new test method using a masking sheet with slits of varying size was developed. Thermal spraying was carried out for a range of spray gun speeds and process parameters. The AE was measured using a broad band AE sensor positioned on the back of the sample as the spot was traversed across it. The results show that the amplitude and energy of the AE signals is related to the spray gun speed, powder used and the oxy-fuel pressure. Using a simple geometrical model for particle impact, the measured AE was found to vary with the energy and number of particles impacting on the sample in a predictable way.
Authors: Can Ming Wang, Hong Fei Sun, Qiang Song, Qiong Qiong Yan
Abstract: Coating blade wears seriously in paper coating process. Wear mechanism was analyzed in this article. A new technology of surface coating process was introduced to increase the hardness of the edge of coating blade and thus to prolong its service life. Surface coating preparing process on blade was studied and metal-ceramic compound coating prepared successfully on the edge of coating blade with AT13 (Al2O3+13%TiO2) wear resistant material by plasma spraying process. NiCrAl alloy powder was used as under coat material. Microstructure of the coating is dense. The coating bonds well with the matrix and have high hardness. Results of grain-abrasion testing show that wear-resisting property of the metal/ceramic compound coating is about 7-8 times as that of steel blade.
Authors: Kyung Man Moon, Mun Jin Nam, Yeon Chang Lee, Yun Hae Kim, Jae Hyun Jeong
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 4th 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
Authors: Nurul Humaira Azhar, Mahesh Talari, Rosmamuhammadani Ramli, Chue Keen Koong
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.
Authors: Elif Nazik Atabay Durul, Macid Nurbaş
Abstract: Electrodeposited hard chromium (EHC) coatings have been widely used for improving wear characteristics of engineering tools and components. In the electrodeposition processes, in general solutions containing hexavalent chromium have been used. Hexavalent chromium is classified as a carcinogen compound, which causes health risks if used in production, and environmental problems due to the toxic character of the wastes [1]. In the present study plasma sprayed coatings (aluminum oxide, Co-28Mo-8Cr-2Si, tungsten carbide, chrome carbide) and electrolytic hard chrome coatings corrosion resistances have been compared through electrochemical polarization tests and immersion test in 0.1 N HCl aqueous solution.
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