Papers by Keyword: Thermal Spray

Abstract: Twin Wire Arc spraying (TWAS) is a well-established method to deposit metallic coatings to protect mechanical components from wear and corrosion. In this work were used coatings that can be divided into two groups: FeCr-based ones and NiCr-based ones. The microstructure, and mechanical properties such as hardness, adhesion, abrasion and erosion resistance were evaluated on these coatings. The wear behavior of the coatings was investigated by Solid Particle Erosion resistance test and by Dry sand/Rubber wheel abrasion test. The aim of this work is to study the wear mechanism by SEM observation of worn tracks.

Abstract: In previous research problem statement occur in hardness to reach the thermal flux between surfaces during movement. The aim of the present investigation has been conducted to study the thermal behavior of ceramic Al₂O₃ (AL-99) coated on a low carbon steel type 1.0060 by using a thermal flame spray technique. The key methods used is microstructural characterization and comparing between experimental data record and numerical program.SEM showed that the Al₂O₃ coatings have a dense microstructure, lamellar morphology and complex of several phases. The XRD analysis of the coating after the spray showed a majority phase of α -Al₂O₃ rhombohedral structure and secondary phase of γ-Al₂O₃ orthorhombic structure. The experimental data recorded From wear indicate two step, first one corresponds to the phase of accommodation between surfaces (samples/ disc), the contact temperature gradually increases to a value Of 75 °C for both pairs, the second step , we could remark from experimental and numerical simulation, it reach 95°C for experimental test and 85 for numerical model.The important findings in tribological results showed that the temperature at the contact is related to the shear stress that will result from the increase of the heat flux. From these results it can be said that the measured temperature increases with the increase of the charge and converges with the contact time. The gap of temperature between experimental and numerical results is probably due to the parameter of microstructure, where in experimental porosities improve convection in the area, in contrast the numerical materials don't add this phenomena.

Abstract: Cold spray additive manufacturing (CSAM) is a promising process for producing metallic layers on different substrates, using powders as a feedstock material. The metallic powders are deposited through pressured gas that reaches supersonic velocities. Due to the low heat input required, as the powders remain in solid-state, this technology is particularly suitable to coat thermo-sensitive materials such as composites. Moreover, the absence of melting allows design freedom, allowing to build complex structures on the substrates, layer by layer. In this scenario, machine learning techniques can be crucial to improve the quality and understanding of this manufacturing process. The aim of this work is to predict the deformation and penetration of a particle upon impact using machine learning techniques in order to assess the properties of the coating. A univariate linear regression method was chosen to verify the feasibility of Theory Guided Machine Learning (TGML) techniques to predict the characteristics of the coating. The training dataset was obtained from both experimental data and computational data. It was confirmed that TGML could be a good route to pursue in order to optimize this process.

Abstract: Thermal Spray Coating is a material surface engineering process, where the coating material is heated until it melts then the melt is pushed with high-pressure air as individual particles or droplets to a surface. This study compares two thermal spray coating methods, twin-wire arc spray and wire flame spray to measure the level of hardness, coating strength and good quality of the coating and porosity. This study used medium carbon steel AISI 1045 as substrate and coating material with FeCrMnNiCSiSP alloy elements (AISI 420). Testing mechanical properties were undergone by hardness testing and pull-off test to determine the coating's adhesive strength. The microstructures were observed using a microscope to test the physical properties. After analyzing the research results, it can be concluded that the twin-wire arc spray coating process produces an adequate level of hardness and coating strength. Twin-wire arc spray can increase the percentage value of substrate surface hardness by 50,56 % and the average coating strength of 21,345 MPa. The microstructure observation results on the coating show that the coating results from twin-wire arc spray have good coating quality with the bonds between the elements contained in the FeCrMnNiCSiSP wire which are bonded to each other and form layered layers and minimal porosity in the coating.

Abstract: The thermal barrier coatings (TBC) are commonly used for protection of jet engine parts. In presented article the influence of chemical composition of TBCs bond coats on isothermal oxidation resistance was analysed. The bond coat was plasma sprayed (APS) using different MCrAlY alloys produced by Oerlikon-Metco: Metco 4451, AMDRY 997, AMDRY 962, AMDRY 365-1, AMDRY 995C. The conducted research showed big difference in coating thickness despite the same spraying parameters. The difference in porosity was not observed. The isothermal oxidation test was conducted during 500h at 1100°C in static laboratory air. The obtained results showed, that degradation mechanism of MCrAlY bond coats regardless of chemical composition is similar. The formation of scale contained aluminium and chromium oxides was observed. The internal oxidation effect was also observed in produced coatings.

Abstract: Thermal spraying is a technology which improves and restores the surface of a solid material. The process can be used to apply coatings to a wide range of materials and components, in order to provide resistance to wear, erosion, cavitation, corrosion, abrasion or heat. In this paper, the study of abrasive and erosive properties of Cr₃C₂/20%NiCr and FeCrB + Al thermal sprayed coating samples were focused. It was revealed that both received thermal spray coating samples show outstanding abrasive and erosive resistance properties.

Abstract: Physical and mechanical properties differences between aluminum and steel, especially melting points, make them unable to be welded easily. Moreover, a hard and brittle intermetallic compound (IMC) is always formed at the interface of aluminum and steel. The thermal spray method was proposed to make interlayer for improving fusion and avoiding hard and brittle intermetallic compounds (IMC) at the interface of joined materials. Based on solubility into both steel and aluminum, nickel was chosen as interlayer material. The aim of this research was to investigate the effect of nickel layer thickness and welding variables on the properties of dissimilar metals diffusion welded between steel and aluminum. Nickel was layered into the steel surface using the thermal spray method before the joining process. The nickel interlayer thickness was in the range from 0.2 mm to 1.0 mm. Steel and aluminum were then welded by using the diffusion weld method. The constant pressure of 5 Mpa and constant holding time of 180 s were performed in diffusion welding, while the temperature was varied, i.e. 500°C, 525°C, and 550°C. The thickness of the formed IMC layer increased along with the increase of the diffusion welding temperature. The highest tensile shear strength was obtained by the joint with the welding temperature of 525°C. The nickel interlayer successfully avoided the formation of Fe-Al IMC and formed a stronger and more ductile diffusion area, and thus increased the strength of the steel and aluminum joint.

Abstract: NiCrBSi coatings were produce by Flame Spray on a carbon steel substrate. The “as spray” coatings were refused by means of Pulsed Gas Tungsten Arc Welding (GTAW-P) process, following different patterns and welding procedure, with objective of optimize the coating characteristics and productivity. The patterns evaluated were oscillated triangular (OT) and oscillated sinusoidal (OS). Travel speed and workpiece-electrode distance were also analyzed. On each obtained sample the surface appearance, macro and microstructure on transverse cuts were evaluated, determining penetration, dilution and level of defects, among others features. Microhardness profiles and adherence were also evaluated. The OS pattern show a more uniform profile of the refused thickness, with less dilution with the base material. Travel speed and workpiece-electrode distance have both significant effect on the volume of refused material, affecting dilution and consequently the resultant coating hardness.

Abstract: Thermoplastic polyvinyl chloride (PVC) is one of the most widely used polymers in the world. Due to its versatile nature, PVC is used extensively across a broad range of industrial, technical and everyday applications including widespread use in building, transport, packaging, electrical/electronic and healthcare applications. In this study, thermal spray technology was used to apply PVC powder on metal substrate. It was revealed that the spray parameters such as working distance, preheat and flame temperature played the important role on the properties of PVC coating.

Abstract: The aim of this research was to optimize the mechanically activated synthesis (MAS) technology of the Cr₃C₂-Ni powder intended for thermal spraying. The MAS production route included ball milling for 72 h (ball-to-powder ratio 20:1) and sintering under 1075 °C in vacuum for 4 h. Sintered compact was crushed, classified by sieving to obtain the fraction suitable for thermal spraying (20–45 μm). The morphology and the phase composition of the powder were analyzed by a scanning electron microscope (SEM) and X-ray diffraction (XRD). The optimal Cr:C ratio found was 7:1. The powder had an equiaxial or a slightly elongated lamellar shape, Cr₃C₂ carbides in a single powder particle had an elongated shape. The principal phases in the optimized powder were Cr₃C₂, Cr₇C₃ and Ni (Cr) solid solution. Coatings from the manufactured powder were produced by the high velocity oxy-fuel (HVOF) spraying. The abrasive wear tests were carried out according to standard ASTM G65. The wear tests showed that the sprayed coatings from the experimental powder exhibited about five times higher wear rate at abrasive wear conditions than the coatings from the reference commercial powder.