Search Results for (marine applications AND ship)

The blast erosion-resistance properties of HVOF thermal spray Cr 3 C 2 type coating system and aluminized material were examined to improve erosion-resistance of turbine housings of compressors used in turbochargers for marine diesel engines. As a result, the erosion life of aluminized material is as same as that of the substrate, on the other hand the erosion life of thermal sprayed coating is ten times of that of the substrate. Therefore, erosion life of turbine housing can be extended by the surface treatment procedure. This technology is applicable to actual products.

In this study, Fe-based amorphous/nanocrystalline coatings with a composition of Fe 53 Cr 19 Zr 7 Mo 2 C 18 Si have been fabricated by high velocity oxygen fuel (HVOF) spray. Postspray annealing treatment at 750°C was employed to enhance the amorphicity of the as-sprayed coatings. The microstructure, corrosion resistance and algal adhesion behaviors of the as-sprayed and annealed coatings were characterized by scanning electron microscopy, transmission electron microscopy, laser confocal scanning microscopy, X-ray diffraction and electrochemical methods. Results show that the as-sprayed coatings exhibited excellent corrosion resistance and decreased algal adhesion, while the annealed coatings exhibited compromised anticorrosion performance but significantly reduced adhesion of algae.

The degradation mechanisms of machine parts are well-known facts, usually resulting in replacement of components. However, in some cases, for instance, parts for large ship engines, repair will often seem more attractive. Time-wise, the vessel’s down-time will be reduced and the investment will be lower. This paper describes repair work performed on valve stems from a 52-year-old ship engine. Due to this long time in operation, the stems were damaged by wear and were no longer functional. The requirements for the stems were scarcely documented stating only a few specific requirements; therefore a short study of the possibilities concerning rebuild material and application method was initiated. This paper illuminates the manufacturing process used; twin wire arc spraying with Monel as the rebuild material. Monel is chosen to meet the requirements for hardness and the subsequent high precision machining. In addition, the mechanical and metallurgical properties of the rebuild coating are examined in regard to adhesion, microstructure and hardness to interpret and support the functionality.

The present study investigates the microstructure and properties of cold spray coatings produced from gas-atomized CuAl10Fe5Ni5 powders. To obtain information relevant to ship rudder cavitation-erosion performance, GL-A shipbuilding steel, equivalent to S235, was chosen as the substrate material. Thick Cu-Al-bronze coatings were deposited on grit-blasted plates using a wide range of parameter sets with different powder treatments, nozzle geometries, gas and substrate temperatures, and particle impact conditions. Coating samples were examined via SEM and XRD analysis, cavitation tests were performed, and bond strengths were measured. Powder and single impact morphologies were also investigated and, along with coating properties and structures, are correlated with spraying conditions. The results indicate that cold sprayed bronze coatings have good potential for ship rudder protection.

To evaluate the corrosion resistance of various coatings applied by the flame spraying method, and to compare their protective properties in sweet- and sea-water samples with seven types of coatings were made, one of them is paint, used to coat ship’s bottom. SEM, Neutral spray salt, according to ASTM B117, erosion-corrosion (E-C) tests in sweet- and sea-water were carried out. The test results showed that coatings based on zinc alloys and polymer are much more effective than standard epoxy coatings and can be compared with expensive zinc-filled paints, because the latter require frequent repairs and repainting. Moreover, the developed coatings are supposed to protect against fouling. At the moment, the fouling tests are continuing.

BIAS Bremen and SLV Rostock have received approval from the classification society "Germanischer Lloyd" for the novel manufacture and replacement of certain engine components with the powder-fed laser-beam plating process. This paper discusses the development of a procedure based on theoretical and experimental examinations on comparable test components. It is observed that, using this simulation tool, a reliable forecast of material conditions, which consequently emerge from the thermal cycle during laser surface treatment is possible. Paper includes a German-language abstract.

The present study compares needed prerequisites for the application of cavitation resistant bronzes by applying different coating techniques, such as cold spraying, HVOF spraying, warm spraying and arc spraying. By optimization to optimum cavitation resistance, the deposited coatings can increase the service life of ship rudders significantly and even serve as repair processes for ship propellers. The given overview aims to support the selection of processes when specifying the target properties to be set with regard to cavitation protection. By using high-pressure warm spraying and cold spraying, properties similar to those of cast nickel aluminum bronze were achieved, however at relatively high costs. In contrast, coatings produced by using HVOF and arc spraying have erosion rates that are only about four respectively three times higher as compared to cast nickel aluminum bronze, while far outperforming bulk shipbuilding steel. Hence, their properties should be sufficient for acceptable service life or docking intervals for ship rudder applications. Propeller repair might demand for better coating properties as obtained by cold spraying. With respect to costs, HVOF and arc spraying in summary might represent a good compromise to reach coating properties needed in application.

For very large structures and parts in critical environments, a materials solution often cannot be found by using one material. The specific desired properties for those structures, like stiffness, ductility, high temperature stability, corrosion resistance, etc. are difficult to fulfill with only one material. In this case a solution may be found by using coatings and design their specific properties to replenish each other by their combination. The Thermal Spraying processes offer the necessary flexibility of producing thin to thick, ductile, soft to hard coatings while due to the wide range of process temperatures it is possible to process a wide range of materials, both as coating and structure. In this paper the some recent and important developments in Thermal Spraying to produce coatings for technical demanding structures will be described. These developments consist of High Power Plasma Spraying, powder- and process control development. To ensure process consistency during long spraying times and to apply reproducible coating quality a suitable process control is of great importance and the development of temperature control by Pyrometry and Thermography will be presented. The example will be drawn according to the application of a coating on a ball valve for off-shore and ship diesel engine parts (piston and valve).

This paper presents the development of a solid homogeneous Aluminum Titanium Alloy wire which can produce, using conventional twin wire arc spray systems, a Thermal Sprayed Anti-Slip coating that will be effective in a range of applications and environments. In addition to its anti-slip characteristic the coating will also provide a hard wearing coated surface that provides corrosion protection to steel substrates. It will be shown that the macroscopically textured coating is extremely resistant to wear and maintains its anti-slip performance for a relatively long period even in high pedestrian traffic areas as assessed using the BS7976-2 2002 Pendulum Test method. Vehicle traffic applications will also be discussed. This paper will also demonstrate that the Aluminum Titanium Alloy has the same corrosion resistance as pure aluminum due to hard intermetallic particles within the alloy being chemically inert allowing this coating to be confidently used in environments in which TSA (Thermal Sprayed Aluminum) coatings are traditionally specified and used. Additionally the properties of the coatings are presented and compared to the wire feedstock to confirm the sprayed layer retains the required elements and all areas are equally durable.

Hot corrosion tests have been conducted on Ni- and Cr-based laser coatings, a high-velocity oxy-fuel (HVOF) sprayed coating and various wrought alloys covered with a synthetic salt of Na 2 SO 4 -V 2 O 5 and exposed at 650°C for 1000 h in air. Coating microstructures and reaction product layers were analyzed with scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The hot corrosion resistance of tested specimen was evaluated by measuring its mean thickness loss. Generally, wrought alloys, HVOF coating and Cr-based laser coatings suffered from selective corrosion beneath salt film, that is, distinct Cr-depleted layer was formed at alloy/salt interface. Cr-based laser coatings exhibited extended solid solubility and they transformed towards equilibrium condition. Cr-rich phases enriched further with Cr and they were prone to corrosion. Low diluted laser coatings and HVOF coating were more resistant to hot corrosion than commonly used industrial standard alloy, Nimonic 80A. Ni-based laser coating exhibited resistance equivalent to Cr-based coatings and superior to corresponding wrought alloy.

This paper discusses the principles of high velocity arc spraying (HVAS) and its use in surface engineering. It also reviews applications in marine environments and power plant boiler pipes, where HVAS coatings provide corrosion protection.

Fast streaming fluid media causes cavitation-erosion in pumps, ship-propellers and rudders. To avoid severe damage, materials with high resistance against plastic deformation and a high fatigue strength should be used. Bronzes fulfill these criteria, but as-cast bulk parts are rather costly. A promising alternative is cold-spray deposition of dense and oxide-free coatings onto exposed surfaces. To achieve high quality bronze coatings by cold-spraying, parameter optimization has to tackle the high hardness of the feedstock powder materials. Additionally, practical limits due to nozzle clogging have to be considered, which may occur at gas temperatures above 700 °C. The present study investigates possible solutions by systematic process parameter and feedstock material optimization, including variation of bronze compositions. Thus, dense coating microstructures and - in consequence - high hardness and good cavitation resistance were obtained. Cold-spray coatings reach up to 8 times better cavitation resistance as compared to conventional ship-building steel (GL-A).

Stainless Steels are required for many applications for ship building as well as for offshore structures such as oil exploration. AISI type 304 stainless steel is not very suitable for such applications as it has a strong tendency for pitting and crevice corrosion. Even type 316 and 317 stainless steels which have respectively 2.5 and 3.5% Mo are not very effective in these environments. Commercially available stainless steels, viz., Avesta 254 SMO is being employed for such applications because of its strong resistance to pitting and crevice corrosion. This is mainly because of high Mo concentration (6.5%). Such steels are not only costly but are prone to form deleterious phases such as delta ferrite and sigma during welding or other heat treatment operations. Hence, an alternative technique to restrict Mo at the surface is needed. In the present work, surface alloys consisting of an austenitic stainless steel with Mo content as high as 10-12% have been formed on stainless steel type 304 substrates. These steels show enhanced passivity and strong resistance to pitting corrosion.

This paper demonstrates the use of commercial simulation software to evaluate a new heater design for cold gas spraying. The gas heater consists of a heating unit and a self-cooling housing. The heating unit is a coiled tube encased in an insulating enclosure. The housing is a double-walled shell through which gas continually circulates, carrying heat away from the outer surface of the insulating enclosure. Simulation results indicate that there is no heat loss in the design as verified by experimental testing.

Nanocomposite epoxies are novel sealants developed especially for sealing metalized coatings. In order to test the corrosion protection performance of arc-sprayed aluminum coatings plus this sealer, steel panels were coated and placed in a corrosion test site on the East China Sea. Test panels were mounted in a marine atmosphere zone, seawater splash zone, tidal zone, and full-immersion zone. Several tests were conducted including corrosion and coating adhesion tests. This paper presents the results obtained from composite-coated steel panels after three years of seawater exposure.

The aim of this study is to determine what types of spray coated metals are desirable for inhibiting iron dissolution in marine environments as a countermeasure against biofilm formation. Experiments were conducted in a closed-loop system in which water continually circulates from a basal water tank through a transparent column where test specimens are immersed. The water flows through an open-air channel on its return to the tank where it is exposed to ambient bacteria. Steel and stainless steel substrates were prepared by plasma and HVOF spraying and, in some cases, a silicon-based sealant was applied. Test specimens were placed in the biofilm reactor and taken out and examined after 5 to 10 days. Substrate surfaces and corrosion products were analyzed by optical microscopy, x-ray diffraction, 3D surface profiling, and low-pressure SEM. Detailed results are presented and discussed in the paper.

Low-velocity oxyfuel-spray and arc-spray coatings of Zn, Zn-Al, Al, and various Al-Si and Al-Mg alloys were tested in immersion and salt-spray conditions with artificial sea water for up to 6,000 hours. Coatings were tested as-sprayed or sealed with fluorocarbon, epoxy or silicone sealants. Comparison and overview of coatings recommended by international and Japanese standards are considered. Coatings Al 99.8 outperformed Zn 99.9 and Zn-13A1 ones while Al-(2.5~5.2)Mg and Al-(5~6)Si showed better corrosion resistance than Al 99.8 coatings. The silicone sealant offered better resistance than fluorocarbon and epoxy organic sealants.

Thermal barrier coatings are used in several industries to improve thermal efficiency. Examples are gas turbine engines and marine diesels. The performance and life of thermal barrier coated components depend on a variety of factors all related to the specific application. This paper gives an overview of some of the aspects to consider and put special attention to. The different features, in the microstructure, will be discussed with respect to their appearance and influence on the performance of the TBC. Thermal conductivity, microstructure, failure mechanisms and different applications are highlighted.

This paper focuses on WC-NiMoCrFeCo composite powder. The effects of high-energy ball milling processes under different conditions on the mechanical alloying of the powder and the acid corrosion resistance of the coating after spraying were studied.

The growing use of thermal spray technology in manufacturing is increasing the need for knowledge regarding the behavior of thermal spray coatings in aggressive environments. Due to the different characteristics of the spraying processes and materials used, the mechanisms of attack can vary greatly from layer to layer depending on the application. This paper presents a detailed investigation of corrosion mechanisms at room temperature and their effect on a wide range of thermally sprayed metals and ceramic-metal (cermet) composites. Paper includes a German-language abstract.