Papers by Keyword: Thermal Spraying

Abstract: Nickel based superalloy materials have being extensively used in aerospace and other high tech industries. In the present work, the effect of different substrates on the mechanical properties of the coating-substrate interface has been studied. To this end, alloy 718, commercially known as Inconel 718, was deposited on alloy 718 and low carbon steel substrates using High Velocity Oxygen Fuel (HVOF) technique at the same condition. The bonding strength of the interfaces evaluated using Vickers indentation test on the coating-substrate interface. Hardness results were subjected to a valid empirical method to estimate the fracture toughness. Results illustrated that using the same material as coating and the substrate led to stronger interface bonding strength due to higher hardness, fracture toughness, and less crack propagation.

Abstract: The knowledge of magnetic and transport properties of construction steels for magnetic circuits plays an important role. Three different techniques: (i) flame spray, (ii) twin wire arc spray and (iii) powder mixture with halide activator were used to produce Si, CuSn6 and Si coatings, respectively, on the 41CrMo4 steel ring substrates. Immediately after the thermal spraying or inserting the steels into the powder mixture was used isothermal heat treatment at the temperatures of 800 °C / 6 hrs, 1000 °C / 4 hrs and 1250 °C / 2 hrs to produce the diffusion coatings. Several coating systems consisting of different phases and thicknesses were manufactured. Opto-digital microscope, scanning electron microscope and digital image analysis, second equipped with energy dispersive microanalyzer, were utilized to characterize the microstructure, chemical composition and thicknesses of the coatings. The influence of coatings on magnetic properties in the frequency range of 50-2000 Hz was also measured.

Abstract: Laser-matter interaction is commonly described regarding three main factors: laser beam, materials and environment. Conversion of absorbed energy via collision process into heat is the most important effect that occurs during laser interaction. Short-pulsed laser beam induces fast transition from the overheated liquid to a mixture of vapor and drops which allows the ablation of micrometric layers. Specific patterns can then be achieved using scanning and automation technology also called laser texturing. New materials with specific properties such as endurance life and/or lower environmental impact attract emerging technologies such as thermal spraying. However, adhesive bond strengths have to be high enough to play a key role in surface properties. A clean surface to enhance mechanical interlocking is a key element. Mechanical and physico-chemical bond strength for thick coatings elaborated by thermal spray process can then be developed using laser. The aim of the present paper is to show the potential of such emerging treatments through new results using various thermal spray processes (thermal spraying as well as cold spraying). Metal or organic materials were investigated implementing various powders.

Abstract: The paper presents the initial results of application of the high sensitivity grating interferometry (GI) method in order to measure the displacement and strain fields in copper and titanium coatings thermally sprayed onto alumina ceramic (Al₂O₃). The residual stresses had been relieved by iterative cutting method, which was applied twice. The displacement maps of u and v were measured after each cut and ε_xx and ε_yy maps were calculated. The results clearly show the presence of ε_xx strains relieved along the second cut. The comparison of both samples confirmed that residual strains in Ti/Al₂O₃ are more significant than in Cu/Al₂O₃ system. The result after relevant postprocessing had been supplemented with the sub-surface principal residual stresses measured in the selected point by the x-ray diffraction method and curvature measurements.

Abstract: Cadmium coatings are used in aerospace and offshore industries for parts in corrosive environments. Since cadmium is a highly toxic heavy metal, it is subject to strong restrictions. Alternatives include Al-based alloys. The present work describes preliminary results for Cd substitution by using Al-Mn with 25 at.-% Mn deposited on 42CrMo4 steel by atmospheric plasma spraying (APS). The prepared alloy powder for the APS process was characterized by laser granulometry, SEM/EDX, and STA. A fraction with particle sizes ranging from 20 µm to 45 µm was used for the thermal spraying process. The APS coating and an Al reference sample were characterized by image analysis, Vickers hardness, and Standard Salt Spray (SSP) testing. The Al-Mn coating exhibits a significantly higher hardness in comparison to pure Al. In both cases, red iron corrosion did not appear during SSP testing. The Al coating was partially covered by a thick oxide film, whereas Al-Mn showed only moderate oxidation but lower adhesion to the substrate

Abstract: Service and downtimes of waste incineration plants generate high expenses for their operators. State of the art is to protect high corrosion exposed components by cladding them with a nickel based alloy. The welded overlay is 2-3 mm thick and very expensive. It needs to be repaired at each service interval. An alternative coating consists of a thermal sprayed multilayer of a nickel based bondcoat and a ceramic topcoat. Thickness and costs of this multilayer are assumed to be in the range of about 10% of the currently used coating. A solvothermal treatment chemically densifies the coating. This leads to a significantly lower porosity whilst improving cohesion and hardness properties. This innovative process leads to a self-healing layer caused by the high temperature waste gas exposition as the driving force.

Abstract: Article deals with the assessment of the properties of ceramic coatings created by thermal spraying technology. Surfaces before coatings deposition were prepared by technology of pneumatic blasting. ZrSiO₄ coating was applied by gas plasma spraying method with NiAl intermediate layer. Mullite coating was applied by water plasma spraying without the intermediate layer and also with NiCr intermediate layer. The quality of the coatings was evaluated by three criteria: adherence of the coatings, REM analysis and EDX analysis. In terms of adhesion of the coatings was found out, that the best properties showed Mullite coating deposited without intermediate layer.

Abstract: This Four passes processing to the thermal spray aluminum coating on the aluminum alloy surface,based on friction stir processing (FSP). Applications SEM, EDS and micro hardness testing to analysis the coatings that have been processed and haven't been processed. The results show that , after the friction stir processing,dense ultrafine grained aluminum with the sizes less than 200nm is obtain ,and replace original laminated and porous coating . Fusion utilizes between the coating and the substrate, the gap between coating and substrate have disappear. The alloy elements in the substrate diffuse to the coating.

Abstract: The oxides in the case of theirs properties are important materials for industrial application especially, in aircraft industry for application as thermal barrier coatings. Thermal properties of zirconium oxide stabilized by yttria are better than other ceramic materials. This powder could be stabilized in room temperature by addition of rare earth elements. In this article the thermal analyses of yttria stabilized zirconia (YSZ) oxide are presented as a baseline for future measurements of thermal properties of YSZ powder with addition of rare earth elements. The thermal expansion, specific heat, thermal diffusivity and thermal conductivity of commercially available Matco 6700 powder offered by Sulzer Metco company were analyzed by thermal methods.

Abstract: High velocity air fuel (HVAF) is one of the high velocity flame spraying process (HVFS). The HVAF method employs a combination of liquid fuel mixed in a chamber with compressed air to obtain high velocity flows. This technology can provide high deposition levels, adequate bond strength as well as high dense coating structure. The working principle of Plasma Spray – Physical Vapor Deposition (PS-PVD) is based on evaporation of the ceramic powder, which enables advanced microstructure of the deposits. In this paper, microstructure of Thermal Barrier Coating (TBC) deposited by HVAF and PS-PVD method was described.