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1-20 of 47
Chromium plating
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Proceedings Papers
ITSC 2022, Thermal Spray 2022: Proceedings from the International Thermal Spray Conference, 900-906, May 4–6, 2022,
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The HVOF sprayed WC-CoCr coatings are widely spread due to their excellent resistance against wear and corrosion. These coatings are one of the most suitable alternatives for hard chromium in many applications. Within the research project, the most suitable hard chromium alternative for hydraulic devices in aircraft is being developed and tested. This application is highly demanding not only on the functional properties of applied coatings but also on the surface quality. Grinding and polishing of the coating are not sufficient, to achieve the necessary surface properties. This study aims to optimize the superfinishing process of HVOF sprayed WC-CoCr coating. The achieved surface quality is primarily measured using profilometry. With optimized surface preparation, the tested parts for aircraft hydraulic parts are treated and tested for leakage of operating fluids and high cyclic lifespan.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 706-711, May 10–12, 2016,
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This study compares the wear performance of thermally sprayed iron coatings with that of electrolytic hard chrome (EHC) plating. Three Fe-based alloy powders (FeSP529, FeSP586, 6AB) were deposited on S355 structural steel plates by HVOF and HVAF spraying and the resulting coatings and plating samples were subjected to dry sliding wear tests using a block-on-ring setup. Wear maps for all three Fe-based powder alloys are similar, showing regions of plasticity dominated wear, wear transition, and oxidational wear as a function of sliding velocity. More importantly, the wear rates of the sprayed coatings were ten times lower than those of the EHC plating samples.
Proceedings Papers
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 162-166, May 11–14, 2015,
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The Under Secretary of Defense mandated all DoD facilities reduce or eliminate Hexavalent Chrome from all processing environments. The USAF Landing Gear Systems Engineering located at Hill AFB Utah is converting all line of sight EHC plating to High Velocity Oxygen Fuel (HVOF) applied tungsten carbide-cobalt (WC/Co) and/or tungsten carbide-cobalt chrome (WC/Co/Cr) coatings. The original HVOF coating thickness of 0.015 inch has been reduced to 0.010 inch due to spallation concerns. This has resulted in the condemnation of many expensive assets due to this coating thickness reduction. ES3 is developing an HVOF applied spall resistant coating for the USAF that may be applied up to 0.030 inch for High Strength Steels (HSS) above 200 KSI stress levels. Material test data and recommendations for use are detailed in this paper.
Proceedings Papers
Fe-Based Powder Alloys Deposited by HVOF and HVAF for Applications Exposed to Solid Particle Erosion
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 1013-1019, May 11–14, 2015,
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HVOF and HVAF deposited coatings of three commercial Fe-based powder alloys have been ranked according to ASTM G76 solid particle erosion testing. The reference was electrolytic hard chrome (EHC) plating. The test results at 30 m/s abrasive particle velocity showed that 6AB powder alloy, when HVAF sprayed, Fe SP586 when both HVOF and HVAF sprayed meet the EHC plating reference erosion rate. 6AB HVOF sprayed and Fe SP529 both HVOF and HVAF sprayed powder alloys achieved two to three times higher erosion rate but were still at the same level of magnitude as the EHC plating reference.
Proceedings Papers
ITSC 2013, Thermal Spray 2013: Proceedings from the International Thermal Spray Conference, 389-394, May 13–15, 2013,
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In this study, WC-CoCr coatings are deposited on grit-blasted steel substrates by high-velocity airfuel (HVAF) spraying. A cross-sectional image of the feedstock powder shows that the WC grains are evenly distributed in the Co-Cr matrix. As-sprayed coating cross-sections are examined under different levels of magnification, coating hardness is measured, and coating and powder phases are analyzed by XRD. In addition, the corrosion behavior of coated and uncoated substrates is analyzed and compared with a reference hard chrome coating.
Proceedings Papers
ITSC 2013, Thermal Spray 2013: Proceedings from the International Thermal Spray Conference, 433-436, May 13–15, 2013,
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In this study, atmospheric pressure microwave plasma spraying is evaluated as a potential coating process for heat susceptible materials. The work was carried out using an experimental setup consisting of a 2.45 GHz microwave generator and a modified plasma torch. To characterize the spraying process, investigators measured plasma temperature, plume shape, and particle velocities for different gas flow rates, nozzle diameters, and spray distances and correlated the results with the flattening behavior of particles as captured in SEM images. Spray trials were then conducted to optimize the deposition of hard chrome on carbon-fiber reinforced polymer substrates and TiO2 powder on stainless steel. In both cases, the coatings were successfully applied; the former by decreasing the nozzle diameter, the latter by reducing heat input to spray particles.
Proceedings Papers
ITSC 2013, Thermal Spray 2013: Proceedings from the International Thermal Spray Conference, 506-511, May 13–15, 2013,
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This paper presents the results of a preliminary study comparing high-velocity oxyfuel and airfuel spraying for the deposition of tungsten carbide coatings as an alternative to electrolytic hard chrome plating. Two tungsten carbide powders with a Co matrix and two with a Co-Cr matrix were sprayed on steel substrates using commercial HVOF and HVAF equipment. The coatings obtained are evaluated by means of SEM and XRD analysis, microhardness and adhesion measurements, and corrosion and wear resistance testing. Detailed results are presented and discussed with emphasis on the role of carbide grain size, carbide contiguity, and binder mean free path. In general, HVOF coatings show significantly higher dry wear resistance, owing to the presence of coarser primary carbides from the initial coarser powder. HVAF coatings, on the other hand, exhibit lower porosity and finer well-distributed primary carbides, giving them an advantage in terms of sliding wear resistance.
Proceedings Papers
ITSC 2010, Thermal Spray 2010: Proceedings from the International Thermal Spray Conference, 278-282, May 3–5, 2010,
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Thermally sprayed alumina coatings are widely used in a range of industrial applications to improve wear and erosion resistance, corrosion protection and thermal insulation of metallic surfaces. These properties are required for many components for production processes in the paper and printing industry. By means of efficient and adjustable coating processes, long-term use of the refined surfaces is obtained. It can be seen that cost-efficient arc-sprayed Al coatings post-treated by plasma-electrolytic oxidation (PEO) form Al 2 O 3 -layers with outstanding hardness, bonding strength, abrasion and corrosion resistance as well as extended service time. These coatings are designed to partially replace hard chromium.
Proceedings Papers
ITSC 2010, Thermal Spray 2010: Proceedings from the International Thermal Spray Conference, 283-288, May 3–5, 2010,
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This paper deals with coating alternatives to hard chromium plating. Indeed, thermal spraying is already used in industry, but results are not always satisfactory for reasons of porosity and microstructures. In this study, atmospheric plasma spraying (APS) and in situ laser irradiation by diode laser processes were combined to modify the structural characteristics of thick NiCrBSi alloy layers. The microstructure evolution was studied and results show that in situ laser remelting induces the growth of a dendritic structure which strongly decreases the porosity of as-sprayed coatings and increases the adhesion on the substrate. Moreover, no phase transition after laser treatment is observed. At least, a mechanical investigation demonstrates that the combination between the plasma spraying and in situ melting with a diode laser can result in the improvement of mechanical properties. The hybrid process appears to be a possible alternative to hard chromium plating, in order to protect mechanical parts, because of the good mechanical behaviour of NiCrBSi layer. Moreover, the increase of the laser incident power causes an increase of the mean contact pressure, along with coatings hardness.
Proceedings Papers
ITSC 2010, Thermal Spray 2010: Proceedings from the International Thermal Spray Conference, 662-668, May 3–5, 2010,
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Pressure to identify alternatives to hard chromium electroplating has increased these few last years, related to environmental requirements, because of the use of hexavalent chromium, a highly toxic substance. The plasma spray technique allows the formation of thick coatings which present moderate adhesion to the substrate and show porosity and formation of oxide interlayers, which impairs to obtain full benefits of the coatings properties. In this sense, a treatment can be necessary to improve the properties of these coatings. In this paper, the effect of an in situ laser melting treatment of NiCrBSi coatings, deposited by plasma spraying was investigated. It is demonstrated by a Life Cycle Assessment (LCA) that this process is clean. Moreover, the corrosion resistance of as-sprayed and in situ remelted layers was evaluated by potentiodynamic polarization curves. The corrosion resistance was increased because of the finer structure and higher densities of the coatings, nevertheless, corrosion mechanisms occurring in all cases are different.
Proceedings Papers
ITSC 2009, Thermal Spray 2009: Proceedings from the International Thermal Spray Conference, 1084-1089, May 4–7, 2009,
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The aim of this study is to propose coatings that could potentially replace hard chromium as a means of corrosion and wear protection. Two NiCrBSi coatings are evaluated, one produced by laser cladding, the other by atmospheric plasma spraying with a post-laser treatment. Although laser-clad NiCrBSi exhibits the best technical properties, the APS coatings were found to be more environmentally justifiable based on the use of life cycle assessment (LCA) software.
Proceedings Papers
ITSC 2008, Thermal Spray 2008: Proceedings from the International Thermal Spray Conference, 212-216, June 2–4, 2008,
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Electroplated hard chromium (EHC) is widely coated onto parts to provide resistance to corrosion, wear and impact. The electroplating process, however, has significant health and environmental impacts. Air emissions during the electroplating process contain hexavalent chromium (Cr+6) - a known carcinogen, furthermore the process is energy intensive and generates hazardous waste. Because of health and environmental issues related to hard chromium plating, there have been several efforts to find alternatives. One of the more efficient technologies among the substitutes is High Velocity Oxy-Fuel (HVOF) thermal spraying. This technology is commercially available today, with a major commercial opportunity in aerospace applications. In this paper, we therefore compare the life cycle environmental footprints of hard chromium and HVOF coatings for aircraft landing gear. Our results indicate that from an environmental perspective, HVOF spraying is generally preferable to EHC plating, with 5-10 times lower human health impacts and 30-50 times lower ecosystem impacts. However, in terms of resource consumption, the processes have similar impact profiles with EHC plating having a potential for lower impact on resources in areas with a significant share of renewable electricity.
Proceedings Papers
ITSC 2008, Thermal Spray 2008: Proceedings from the International Thermal Spray Conference, 1321-1325, June 2–4, 2008,
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High velocity oxygen fuel (HVOF) sprayed WC coatings have been found wide applications as substitutions of chrome plating in the airplane industry. The wear of HVOF WC coated landing gear against Al-Ni-Bronze alloy leads to the wear or spalling of WC particles, and finally results in the degradation of sealing property for landing gear system. WC-Co coating with nano-size WC particles is expected to exhibit good wear resistance, and the weight loss of Al-Ni-Bronze alloy can also be reduced, which is beneficial to the sealing property of landing gear system. Three types of coatings are prepared using agglomerated, sintered nano-scaled WC-12Co, conventional WC- 12Co and WC-10Co4C powders, respectively. The wear behaviors of the as-sprayed coatings against Al-Ni- Bronze alloy are investigated at the different loads and linear velocities. The study is expected to provide the basis for the application of HVO/AF nano-scaled WC coating in landing gear.
Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 911-915, May 14–16, 2007,
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HVO/AF (High-Velocity-Oxygen/Air-Fuel) WC-17Co and WC-10Co4Cr coatings exhibit great potential in the replacement of electrolytic hard chrome (EHC) coating, and comprehensive properties of such coatings should be not worse than those of electrolytic hard chrome coating. The impingement-resistance of HVAF coatings sprayed on 300M ultra-high strength steel was studied in this paper. As an important property index, the fracture toughness of HVAF WC coatings was measured using micro-indentation method at the load of 9.8, 19.6, 24.5, 29.4 and 49.0N respectively. The cracks resulted from stress concentration in the micro-indentation were analyzed. The impingement-resistance for two HVAF WC coatings and EHC was evaluated according to the ASTM D3170 standard, and steel ball dropping experimentation was performed at the height of 0.61, 1.52, 1.83, 2.36 and 2.59m respectively. The cracks caused by both impingements were analyzed using SEM and optical microscopy in comparison with cracks in micro-indentation test.
Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 1011-1016, May 14–16, 2007,
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For deposition of protective coatings different coating techniques are available. Usually, detailed evaluation of various deposit types and materials is necessary for selection of the best suited coating for specific application fields and demands. Subject of this work are thermally sprayed functional coatings applied as wear (and corrosion) protective layers. Examination of different optimized thermal spray coatings, i.e. HVOF sprayed WC/Co(Cr) and Cr 3 C 2 /NiCr coatings, conventional flame sprayed and fused self fluxing alloy coatings reinforced by hardmetal and APS sprayed oxide Al 2 O 3 /TiO 2 and Cr 2 O 3 coatings, is done in comparison to thick hard chromium platings. Two abrasive wear tests featuring wear by lose abrasive particles are carried out. These impart dry wear conditions according to ASTM G65 (Rubber Wheel test) and wear by abrasive suspensions according to ASTM G75 (Miller test). The work also contains evaluation of newly developed HVOF torch components permitting increased combustion gas, and therefore also particle, velocities concerning the benefit in terms of coating properties. Exemplary evaluation of the new components influence on velocity and temperature of spray particles is carried out by comparative SprayWatch analyses. Both the influence on the coatings microstructure and the wear performance are studied. Coating microstructure is evaluated qualitatively by optical and scanning electron microscopy and the micro hardness HV0.3 is measured. Worn surfaces are studied by SEM in order to deduce wear mechanisms.
Proceedings Papers
ITSC 2006, Thermal Spray 2006: Proceedings from the International Thermal Spray Conference, 1399-1406, May 15–18, 2006,
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Electroplated chromium improves corrosion resistance while providing resistance to wear, fatigue and impact. However, hard chromium plating uses chromic acid, which releases fumes containing carcinogenic chromium +6 ions into air during the process. Therefore, numerous efforts have been carried out worldwide in the last decade to develop alternatives and several applications and processes were validated, among which trivalent chromium plating, electroless nickel and nickel alloy coatings, micro-welding, PVD, CVD, and thermal spraying. Nevertheless, these finishing processes have impacts on human health, ecosystems and resources. In this work, a Life-cycle assessment (LCA) methodology based on Eco-indicators 99 was used to compare the environmental impacts and benefits of thermal spraying (including APS- and HVOF-sprayed WC-Co coatings and TWEA- and APS-sprayed hard steel coatings) to conventional chromium plating.
Proceedings Papers
ITSC 2006, Thermal Spray 2006: Proceedings from the International Thermal Spray Conference, 1463-1466, May 15–18, 2006,
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The increasing use of HVOF (high-velocity oxy-fuel) coatings to replace hard chrome plating was initially motivated by the environmental and health risks associated with hexavalent chromium (Cr 6+ ) emissions during the plating process. Following performance optimization and proper coating selection, it has been found that the potential increase in performance and the cost/process-time reduction offered by the HVOF process often justifies its application. Recently, the use of Cr-containing alloys processed by HVOF has drawn attention to the potential release of Cr 6+ during heating of metallic chromium. For instance a new California regulation for airborne toxic control measures to reduce emission of hexavalent chromium from thermal spraying is in preparation. The present study focused on monitoring operator exposure during the HVOF spraying of WC-10%Co-4%Cr. The spraying was performed using a JP-5000 HVOF gun in a spray room in which a ventilation flow rate of 10,000 scfm was imposed. Air sampling was taken in the spray room as well as in the adjacent control room in accordance with the NIOSH 7300 and 7600 standard methods. A portable sampler attached on the operator’s chest was also used to monitor the operator exposure during a typical workday. Results indicate that even though metallic fumes of Co and Cr are present in the spray room during spraying, the hexavalent form Cr 6+ is not detected. It was concluded that an operator entering the spray room for a limited amount of time with the gun in operation would be exposed to only low fume levels that can still be reduced by wearing an appropriate respiratory mask.
Proceedings Papers
ITSC 2006, Thermal Spray 2006: Proceedings from the International Thermal Spray Conference, 1339-1344, May 15–18, 2006,
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Conventional decorative chrome plating operations are known to be environmentally and occupationally hazardous because of the use of hexavalent chromium and other toxic chemicals. An alternative ArcBright™ chrome technology has been developed to eliminate these hazards and simultaneously simplify manufacturing methods in this industry. The application method presented here uses an organic base coat and a physically vapor deposited (PVD) chrome to replace electroplated copper-nickel-chrome structure. An advanced rapid cycle, high rate PVD chrome coating method has been developed for this application to be able to increase throughput to the levels required in the automotive sector and to minimize application cost. The technology is applicable to many metals, plastics, composites and other solid materials that are not possible by conventional electroplating providing a wider choice of substrates. The PVD chrome process has been characterized and the ArcBright chrome has been qualified to automotive specifications.
Proceedings Papers
ITSC 2006, Thermal Spray 2006: Proceedings from the International Thermal Spray Conference, 1295-1300, May 15–18, 2006,
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With the vast array of coating technologies and materials available in the marketplace, matching the best coating to an application is far from a trivial task. There is a tendency on the part of vendors, for example, to put forward any hard coating as a chrome replacement or any corrosion-resistant coating as an alternative to cadmium. At the same time users often attempt to shoehorn the coatings with which they are most familiar into applications for which they are not well-suited. This paper will discuss how best to match the application to the best technology and material, considering all the critical requirements of fit, form and function, with particular reference to alternatives for chrome and cadmium plating.
Proceedings Papers
ITSC 2006, Thermal Spray 2006: Proceedings from the International Thermal Spray Conference, 615-618, May 15–18, 2006,
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The Airbus A380 program marked the Goodrich Landing Gear introduction of High Velocity Oxygen Fuel (HVOF) applied tungsten carbide cobalt chrome (WC-Co-Cr) coating as a replacement coating for electrolytic hard chrome. HVOF is a new coating technology when applied to aircraft landing gear so specifications for coating application, finishing, powder and supplier qualification were developed to reflect the unique function of landing gear components. Since the materials, sizes and shapes of landing gear components are dissimilar to other aerospace parts currently HVOF sprayed, the capabilities of each spraying and grinding supplier needed careful assessment. Both suppliers and internal customers required training on the requirements specific to landing gear. This paper will discuss the development of HVOF specifications specific to aircraft landing gear, the methods developed for qualifying HVOF suppliers, and some challenges encountered when introducing HVOF-applied WC-Co-Cr as a hard chrome replacement.
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