In this study, nickel-base superalloy coatings are deposited on CrMoAl substrates by different spraying methods and the coatings are evaluated based on their microstructure, phase composition, surface and splat morphology, bond strength, and corrosion properties. In the experiments, NiCrAlY powders with a particle size range of 30-45 μm were sprayed by conventional air plasma and a new laser hybrid plasma spraying technique. The spraying parameters are presented along with test results, observations, and conclusions. The coatings produced by laser hybrid plasma spraying had an average porosity of 0.9%, a bonding strength of 117 MPa, and significantly better corrosion properties than the APS layers.

This study assesses the effect of different alloying elements on the microstructure, oxygen content, hardness, and corrosion resistance of stainless steel coatings produced by atmospheric plasma spraying. SUS836L stainless steel powder with Si, Mn, and B additions served as the base feedstock alloy to which different amounts of B, C, Mo, Ti, Nb, V, and Cu were added. The powder mixtures were sprayed on carbon steel substrates and the deposits were examined and tested. The results show that B and C additions of 2-3% have a beneficial effect, but at 5% cause a drop in corrosion resistance that proved to be remediable through the addition of Cu, which improves the corrosion potential of the matrix phase by its combined action with Mo, Si, and B. The effect of Ti, Nb, and V, which are added to suppress Cr oxidation in molten alloy particles during flight, is that it promotes that formation of fine carbide and boride compounds, increasing hardness without sacrificing corrosion resistance. In addition to these findings, the study also shows that the coatings developed are in many ways comparable to Ni-based self-fluxing alloy coatings.

Hydraulic turbines, valves, and pumps operate in environments where they are exposed to cavitation phenomena and corrosion, which can result in mass loss, leading to reduced performance and failure. HVOF spraying has been used to repair eroded surfaces on such components and new alloys are being developed to reduce repair costs. This investigation assesses the cavitation resistance of FeMnCrSiNiB alloy coatings deposited by HVOF spraying. Corrosion rates and oxidation potentials are measured under different conditions and compared to stainless steel coatings normally used on water turbine runners.

The economic use of offshore wind turbines requires a reliable and long-lasting corrosion protection. Sophisticated multilayer coating systems consisting of a thermal spray coating – mainly ZnAl15, a sealer and several layers of organic coating – have been proven to provide such protection. Damages to these duplex-coatings can, however, not be prevented necessitating on-site repair. In case of severe damages, the remaining coating close to the damage is often removed and subsequently, the duplex coating is rebuilt from scratch. In the present study, two integrated coating removal and substrate pre-treatment methods are investigated. For this purpose, duplex-systems were produced, artificially damaged by milling and afterwards treated by either grit blasting or with a rotating steel-wire brush, i.e. a Monti Bristle Blaster. Afterwards, the duplex coating was re-applied in the considered area. To evaluate the influence of the pre-treatment method on the coatings’ corrosion protection potential, a 38 week-long salt spray test was used. The test revealed a pronounced influence of the pre-treatment method on the corrosion protection potential. In case of grit blasting, no substrate corrosion could be detected. The use of a Bristle Blaster, however, resulted in coating failure and some spots of red rust.

In this study, alumina coatings are deposited by atmospheric plasma spraying and sealed using an aluminum phosphate solution containing a small fraction of alumina nanoparticles. Potentiodynamic polarization, electrochemical impedance spectroscopy, and salt spray tests are used to evaluate the corrosion behavior of both the as-sprayed and sealed coating samples. Besides improving corrosion resistance, the sealing treatments are also shown to increase the electrical resistance of the coatings, making them better electrical insulators.

This work introduces a hybrid spray-and-fuse process and a modified CoCrMoC (Stellite) alloy that significantly expand the manufacturing window for wear-resistant coatings. The Co-based alloy was produced by adding Ni, B, and Si to Stellite 720 to lower its melting points and expand its melting range thereby improving the sprayability and fusibility of the material. The modified alloy was deposited on Inconel 718 balls and 1 in. diameter coupons by HVOF spraying and coating samples were sinter fused at high temperatures followed by furnace cooling. The processes used are described and test results are presented, showing that thick, metallurgically bonded coatings were achieved with high hardness and excellent wear and corrosion resistance.

In this investigation, different atomizing gases, arc wire spray guns, and wire sizes were used to deposit ZnAl coatings on high-strength steel substrates. Sample sets corresponding to different gas mixtures and pressures as well as other parameters were produced and the coatings obtained were evaluated based on morphology, porosity, composition, phase distribution, and oxide content. The results are presented and discussed, particularly with regard to corrosion lifetime and performance.

This study investigates the formation of ZnNi/Cr 2 O 3 -TiO 2 -CuO-SiO 2 /PTFE composite ceramic coatings by atmospheric plasma spraying and assesses their ability to improve the corrosion, friction, and wear performance of reciprocating parts. The as-sprayed coatings were examined then subjected to a series of tests to evaluate corrosion and fouling resistance. Reciprocating parts that had been coated were relatively intact after 5000 h in a realistic ocean environment. Cyclical changes in coating weights were found to be influenced by the dissolution of oxide films and the accumulation of secondary products. PTFE proved to be an effective sealing agent, reducing mass loss and porosity by approximately 30%.

In this work, the aim is to develop a cost-effective coating to protect cast iron and carbon steel from corrosion and wear. An alloy with a composition of FeCr25Mn10BC was designed that could be readily converted to powder form by gas atomization. Different sized powders were produced, characterized, and subsequently sprayed using a three-cathode air plasma generator. It was found that fine powders with fractions of -25 +10 μm and -10 μm had a much higher affinity to oxidation than coarser ones. Nevertheless, using suitable parameters, dense coatings with low oxide content could be realized even with the finest powder. The results show that full utilization of the powder is achievable due to the wide parameter window of three-cathode plasma spraying and that the average deposition efficiency is more than 70%. In addition to savings in material and processing costs, the new alloy system provides greater wear resistance than stainless steel coatings and exhibits significantly higher corrosion resistance than unprotected cast iron and carbon steel.

In this study, the in-situ corrosion behavior of an Fe-based amorphous coating is investigated in a simulated deep sea environment (80 atm). FeMoCrYCB powder produced by gas atomization was deposited on 316L stainless steel substrates by HVOF spraying. The amorphous iron coatings exhibited greater pitting resistance than stainless steel under high hydrostatic pressures, evidenced by higher pitting potential, longer pitting incubation time, and reduced pitting growth. Passive films that formed on the amorphous coatings were also analyzed and found to be thicker, more uniform, and harder than those that developed on 316L stainless steel, indicating that the former are more difficult to break down and more resistant to Cl- ion penetration.

This work investigates the biofunctionality and corrosion resistance of titanium (Ti) and Ti/bioglass composite coatings. Commercially pure Ti (CP-Ti) and 45S5 bioglass powders were deposited on CP-Ti plates by air plasma spraying and the coating samples were placed in Hanks’ balanced salt solution for simulated body fluid (SBF) testing. After four weeks of immersion, the coatings were examined by SEM imaging and EDS and XRD analysis. EDS analysis showed that the Ca content on the Ti/bioglass coatings increased from 4 to 16 wt%, while no increase in Ca was observed on the Ti coatings. Hydroxyapatite formation was found on both coatings, although the relative intensity of HA on the XRD spectrum was higher for the Ti/bioglass composite layers. Weight measurements before and after immersion showed that the CP-Ti samples experienced a mass gain and that the Ti/bioglass samples underwent a mass loss likely due to the dissolution of calcium and phosphate.

A nanostructured WC-CoCr coating was fabricated by HVOF spraying using a new type of WC-CoCr powder in which the CoCr exists in the form of a metallic compound. The CoCr powder constituent was prepared by induction melting and mechanical milling. It was then combined with a WC-Co composite nanopowder and the mixture was agglomerated by spray drying and heat treating. The powders and coatings produced were characterized by means of XRD, EDS, and BSE analysis, nanoindentation testing, and potentiodynamic polarization studies. The results show that the presence of the intermetallic CoCr compound makes nanostructured WC-CoCr coatings harder and much more corrosion resistant than conventional WC-Co-Cr coatings in which Cr exists as an unalloyed metal.

Thermally sprayed aluminum (TSA) coatings have been successfully used to mitigate corrosion of carbon steel in offshore service, but concerns regarding its suitability in CO 2 -containing solutions have kept it out of the running for emerging carbon capture and storage applications. This paper presents the results of a 30-day test in which carbon steel specimens protected by TSA coatings were immersed in deionized water at ambient temperature in 0.1 MPa CO 2 . Acidity and corrosion potential were monitored during the test and dissolved Al 3+ ion content was analyzed at the completion. Based on experimental results, thermally sprayed aluminum is a viable candidate for corrosion mitigation in CO 2 -containing water as would be encountered in carbon capture and storage applications.

WC-Co and WC-Co-Cr coatings were deposited on Q345 steel substrates by HVOF and plasma spraying. Coating hardness was measured and corrosion and wear tests were conducted. In terms of hardness and density, the HVOF sprayed WC-Co coating is shown to be superior to its plasma sprayed counterpart. The WC-Co-Cr coatings, on the other hand, exhibited better wear and corrosion resistance, especially the coating produced by HVOF spraying.

This paper aims to clarify the development and characterization of cold-sprayed aluminum coatings on a non-regular medium-carbon steel surface. The work is carried out with a two-fold purpose: to optimize the deposition process and coating thickness and to learn how substrate defects and imperfections influence coating performance and the corrosion resistance of the coated material.

This study demonstrates a novel method for improving the corrosion resistance of cold sprayed Al6061 coatings. Large stainless steel particles were added to a commercial Al6061 powder and the mixture was deposited on Mg alloy AZ31B substrates using nitrogen gas at low working pressure and temperature. It is shown that the stainless steel particles had a shot-peening effect, thus increasing the density as well as the corrosion resistance of Al6061 coatings. SEM examination showed that no stainless steel particles were incorporated in the coating.

In this study, TiB 2 -40Ni and TiB 2 -50Ni powders are deposited on mild steel substrates by HVOF spraying in order to investigate the influence of Ni on coating hardness and corrosion, wear, and thermal shock resistance. The surface morphology and cross-sectional microstructure of the ball-milled powders and composite coatings are examined, and various tests are conducted to measure properties of interest. The findings are presented and discussed in the paper.

The aim of this study is to evaluate the microstructure and corrosion properties of Fe-based coatings produced using different HVAF spray guns. Differences in microstructure, phase composition, porosity, oxide content, and corrosion behavior were observed among the coatings depending on the gun and spraying parameters. The results are presented and discussed in detail.

This study evaluates the corrosion and wear resistance of WC-Co coatings produced by cold gas and HVOF spraying. Three WC-Co cermet powders varying in cobalt content were deposited on aluminum alloy substrates by both methods. The powders were characterized based on microstructure, particle size distribution, and phase composition, and the coatings based on cross-sectional microstructure, phase composition, and Vickers hardness. The coatings are also compared based on the results of ball-on-disk, rubber-wheel, and electrochemical testing, which shows that CGS has several advantages over HVOF spraying for the deposition of WC-Co coatings.

The aim of this study is to compare the quality of corrosion-resistant thermal spray coatings depending on where and how they are applied. ZnAl 15 coatings were applied to S235 steel substrates by wire arc spraying in keeping with standard (EN ISO 2063) practice. The coatings were sprayed under factory conditions and in a simulated onsite environment using manual and automated methods. As-sprayed and sprayed-and-sealed coating samples were subjected to climate-cycle and corrosion testing. Coatings applied onsite varied in quality to a much greater extent than those sprayed under workshop conditions. Poor quality, and implicitly a lower corrosion resistance, was widely detected in coatings where ZnAl was manually sprayed under simulated onsite conditions. The implications of the study are particularly relevant to the sustainability of coastal and offshore wind power generators due to maintenance challenges.