Papers by Keyword: Coating

Abstract: Chromium carbide coatings deposited on mechanical parts by different techniques have an interesting hardness, wear-resistant and corrosion resistance. Some studies show that chromium carbides produced by physical vapor deposition methods and revealed a superior hardness present a poor adherence to their substrates. The objective of this study is to indirectly obtain a hard, and adherent coating of chromium carbide by using a conversion treatment including carburizing treatment of steel substrate, deposition of a pure chromium layer, and annealing treatment of coated carburized steel under a carbonic gas atmosphere. Treatment temperature has an effect on the partial or complete conversion of chromium film as a result of the diffusion and precipitation process. The transformation rate of chromium into both chromium carbide layers was investigated. For 1 h of holding treatment, chromium film was totally transformed at 900 °C into chromium carbide film which presented high hardness and excellent adhesion.

Abstract: The surface has a vital function in the tissue's response to the presence of foreign material in the field of body implants. Surface modification with coatings can be adjusted to provide the highest service performance at the lowest cost. Coatings can increase corrosion resistance by reducing metal ion and corrosion product migration in the body. We fabricated polymer based bio-composite coatings by blending chitosan (Chi), alginate (Alg) and nanoparticles ((TiO₂, Nb₂O₅) by dip coating onto a 316L stainless steel substrate. The coatings’ surface morphology and phases were studied using FESEM and FTIR analysis. The wettability behavior of the coated samples was also studied by investigating their contact wetting attributes. The antibacterial activity of the functionalized coatings was determined too. The FTIR results showed that the blending of Chi-Alg and nanoparticles was excellent, and no obvious differences in the spectra or any changes in the structures of the polymer matrices were observed. The SEM results demonstrated that the coating layers were uniform, homogeneous, and crack-free on the 316L Stianless steel substrate when using TiO₂-Nb₂O₅ nano particles. The contact angle results showed the highly hydrophilic properties of the pure chitosan-alginate blend. As well, coatings containing nano particles showed the same antibacterial effect of chitosan-alginate blend coating.

Abstract: This work describes the advances in manufacturing for the recovery of hydraulic turbines. One of the key components in the operation of hydraulic turbines is the blades; as they are part of the impeller, they are in constant motion and directly receive all the loads produced by the impact of the water and the abrasive effects caused by sediment. The interaction between abrasion, cavitation, and corrosion accelerates the wear of these components, so it is necessary to apply coatings to prolong their useful life. When these elements lose their hydrodynamic profile, they must be submitted to a recovery process; typically, welding is used. However, due to the advancement of additive manufacturing (AM) and the development of new materials, AM appears as a disruptive technology capable of recovering the dynamic profile and improving surface properties such as hardness and wear resistance. The results show the effectiveness of the wire and arc additive manufacturing technology for the recovery of hydraulic turbines, increasing surface hardness from 285 to 325 HB.

Abstract: This paper deals with the chemical analysis of the coating on building materials which were used for construction of Mánes bridge in Prague. It is a historical bridge which is more than a hundred years old. Using the method of infrared spectroscopy, we can determine the organic and inorganic compounds in coatings, adhesives, grout, and polymer materials. The organic compounds are added into the concrete and other building materials due to improvement of physical and mechanical properties such as compressive strength, tensile strength, modulus of elasticity or water absorption. The building materials can be covered with the coating for protection against mechanical damage. The chemical analysis of the building material is important to know before reconstruction and remediation of the historical buildings. As a result, the infrared spectrum of the coating was measured and it was determined that the coating was on the acrylate base.

Abstract: In this study, the corrosion protection behavior of fumed SiO₂ reinforced epoxy composite coatings applied on steel substrates was evaluated and compared to graphene-epoxy nano-composite coatings. Graphene-epoxy nano-composite coatings provide excellent corrosion protection but the uniform dispersion of graphene in polymer solvent is a challenge. So, the fumed silica was chosen as the reinforcement rather than graphene. Fumed silica was treated with stearic acid and used with epoxy to get hydrophobic and corrosion resistant coatings. The partial carburization of epoxy was carried out to get carbon layer on steel substrate. The epoxy was cured at various temperatures (200, 250 and 300 °C) to see its effect on hydrophobicity and corrosion behavior of the composite coatings. Presence of different functional groups of modified silica and epoxy was confirmed by FTIR ATR. Coating prepared from this material was evaluated microscopically with respect to structure, uniformity and interface with optical microscope. Polarization effect of coatings was studied by potentiodynamic polarization method. Coating thickness was measured by an Elcometer gauge, and these were checked by the micrographs at 50, 200 and 1000x. E250 (60% epoxy + 6% Silica) showed corrosion rate of 0.017mpy much lower than uncoated steel substrate (2.612mpy). Contact angles for npc200 (neat partially carburized epoxy cured at 200°), 4Si70 (60% epoxy+4% Silica cured at 70°), 6Si300 (60% epoxy+6% Silica cured at 300°) and 6Si250 (60% epoxy+6% Silica cured at 250°) were 90°, 89.5°, 72.5° , 97.5° respectively. So, it was proved that partially carburized epoxy coating with 6% modified silica cured at 250 °C was more corrosion resistant and hydrophobic in nature.

Abstract: Thermal energy storage (TES) systems have paramount importance in the design of Concentrating Solar Power (CSP) plants. TES systems allow storing the energy collected from solar radiation as heat energy in a thermal fluid and, in that way, extending the energy duration period of the plant and making the produced electricity dispatchable, depending on the actual demand and not only on the availability of the sun. The thermal fluids, synthetic oils, or molten salts, usually operate at temperatures from 500°C up to 800°C. The harsh operative conditions bring out issues related to the compatibility with the construction materials of CSP components, i.e., carbon and stainless steel. Coating of low-alloy structural steel with high-resistant materials has been addressed as a promising solution for mitigating the corrosion in TES system components. Compact plasma spray process was used to deposit Inconel 625 alloy onto T22 carbon steel coupons. Nitrate salts mixture, 60%NaNO₃-40KNO₃, commonly employed in CSP systems as operative and thermal storage fluid was used as corrosion medium. The tests were conducted by immersing coated and uncoated samples in molten salts at 500°C for 1, 3 7, and 14 days to assess the corrosion behavior of the In625 coatings. After 24 hours of exposition to molten nitrate salts, the T22 surface showed a pronounced oxidized layer having a thickness of approximately 20 µm. This layer is mainly composed of oxygen, iron, and chromium, which are the main constituents of carbon steel, with a few traces of sodium and potassium derived from the reaction of salts with the steel. Inconel 625, on the other hand, showed the formation of very thin scales of corrosion products localized only on the surface of the sample. Longer exposition is expected to produce a more pronounced degradation of uncoated steel, but barely affect the Inconel 625 coating

Abstract: In electromagnetic embossing, the interaction of the magnetic field and the induced current density results in body forces that enable the replication of optical microstructures into thin sheet metals. However, as the sheet metal is completely penetrated by the magnetic field, electromagnetic properties of the dies need to be considered in process design, as they influence the forming conditions by changing the field distribution, force vectors and eddy current densities. With die coatings like electroless nickel–phosphorus (NiP), the electromagnetic properties of the die change. Therefore, the effect of both - die substrate and coating material - was studied to find advantageous conditions for electromagnetic embossing. Within two-dimensional electromagnetic field simulation, the electromagnetic properties of coating and substrate material were varied in addition to the coating thickness. To validate the results, electromagnetic embossing experiments were carried out. Here, different dies were fabricated from aluminum (uncoated) and cold work steel with 200 µm and 400 µm thick electroless nickel–phosphorus coatings that were subsequently micro-structured in optical surface quality. It was demonstrated by numerical and experimental results that the coating and the substrate influence the electromagnetic embossing significantly in correspondence to their shielding behavior and field interaction due to electromagnetic properties and coating thickness.

Abstract: As global warming continues, functional textiles with moisture/thermal management performance are becoming more and more important. In this paper, a cationic hydrophilic polymer (CHIP) was developed, and combined with flexible and simple coating methods to achieve durable moisture/thermal management of polyester fabrics. The as-prepared fabrics exhibit excellent washing fastness, the wettability of the coated fabrics can withstand 150 home laundry cycles. Owing to its firm fixation, the methods of single-side spraying and templated-spraying were adopted to achieve water/sweat unilateral penetration or directional transport through polyester fabrics, which realizes the timely and directionally transport of sweat as well as thermal in fabrics. This work is useful for design of high-performance moisture/thermal management fabrics for various applications, e.g., quick-dry sportswear, outdoor uniforms, and other functional garments.

Abstract: This study reports the influence of Ni content on the structure and wear resistance of (Ti, Cr)C-based coatings. The (Ti,Cr)C-based composite powders, cladded with 18, 25 and 33 wt.% Ni were used to deposite coatings on stainless steel substrate by detonation spraying technique. The thickness of the coatings reaches 350-500 μm, the porosity is about 2%. The (Ti,Cr)C-Ni coatings have a dense lamellar microstructure with uniform distribution of refractory particles and metal binder. The wear behavior of the coatings against steel ring were investigated by dry sliding wear tests. Depending on the Ni content the sliding wear loss of the (Ti,Cr)C-based coatings was 1,2-2 times less than that of (Ti,Cr)C detonation-sprayed coating. The investigation of worn surfaces revealed that the wear mechanism of the (Ti,Cr)C-based coatings with Ni content increase changes from abrasive to oxidative.

Abstract: This research aimed to reduce die and punch wear and improved the quality of the production process with the application of the Lean Six Sigma methodology. Die and punch had limited capability in cutting material edges in the case study company. The root-cause analysis showed a correlation between the hard coating and the lubricant effect on wear reduction using the design of experiments and DMAIC based on the Six Sigma approach. The results indicated that a combination of AICrN-PVD coating and aloe vera oil provided the most outstanding results in terms of wear reduction. Moreover, it had the potential to minimize the cost of product defects or repairs significantly. These findings showed the effect of the Lean Six-Sigma approach at the die production process, which increased operational efficiency and consistency to enhance business performance and meet customer requirements.