Whenever large amounts of liquids or gases have to be transported over long distances, steel pipelines are used. They supply industry with raw materials, guarantee drinking water supplies to large cities, and convey energy sources around the globe. Despite the most stringent safety regulations, pipelines regularly suffer damage and leaks. Severe environmental pollution occurs when oil or gas pipelines, in particular, are damaged. In the case of both onshore and offshore pipelines, decontaminating the affected areas involves a great deal of time, effort, and cost. Moreover, in most cases the contamination cannot be eliminated completely. There are various reasons for damaged pipelines. Corrosion poses one of the greatest challenges here, and this can be influenced by the pipeline owners. There is a need for safe and reliable corrosion protection, and this is set to grow over the coming years. Based on current market data, between 13 and 18 million tons of line pipe were delivered in the years 2015 to 2020. This corresponds to a pipeline length of approx. 86,000 km per year. The objective of this paper is to illustrate why the corrosion protection currently used fails to work in some cases. It also aims to show how thermal coating can improve corrosion protection and what requirements its technical implementation must fulfil. To this end, line pipe is presented in the next chapter. Common standards and manufacturing processes are introduced. The third chapter outlines current corrosion protection measures. Moreover, weak points are analyzed by looking at damage that has already occurred. The requirements for thermal coating are determined based on this.

The paper looks at the results of TSPC research to develop coating technology for threaded surfaces in pump and compressor pipes (PCP) used in the oil and gas industry.

In this study, twin wire arc spraying is used to bond wire mesh to the outside surfaces of stainless steel pipes in order to increase heat transfer surface area. At the optimum spray distance, the oxide content, porosity, and adhesion strength of the coatings are shown to be 6.6%, 2.1%, and 24 MPa, respectively. Pipes with different wire mesh configurations were placed in an oven and heated to temperatures from 300 °C to 900 °C. Water temperatures were measured at the inlet and outlet of the pipe for flow rates between 0.2 and 0.5 gpm. A maximum water temperature rise of 13 °C was achieved, corresponding to a total heat flux of 57 kW/m2. Heat transfer efficiency is shown to depend strongly on the quality of the bonds between the wire mesh and pipe and the spacing of wires in the mesh.

This work studies the manufacturability of pyramidal fin arrays produced using cold gas dynamic spraying. Near-net shape pyramidal fins of various sizes were formed and tested. The fin arrays were characterized and their heat transfer properties were assessed. Results obtained correlate well with data published for banks of tubes at a similar dimensionless pitch, and show that fins produced by cold spraying outperform traditional straight-cut fins at the same fin density.

A numerical investigation of fluid flow and heat transfer through thermal spray formed metal foam heat exchangers is presented. Experimentally obtained fluid flow and heat transfer parameters are used in the simulations. Analytically obtained values of effective thermal conductivity are used to model heat transfer. A 3D CFD model was created for a metal foam heat exchanger with a square cross-section. The external walls were deposited on the foam using a wire-arc process. The channel walls of the foam were exposed to a constant temperature of 400 K and an air flow with an inlet velocity of 2 m/s. The model was verified by comparing sample results to experiments. The effect of the foam on heat transfer was then studied by varying thermal conductivity values.

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.

Heat exchangers play a vital role in ongoing efforts to conserve energy. Plate-type heat exchangers typically consist of two flat separated flow paths in which heat transfer enhancing matrices are inserted. The combined effects of small irregular hydraulic diameters along with elevated heat transfer areas results in highly-efficient heat transfer to the external fluid. This allows for very versatile and compact heat exchanger designs. Typical plate-type heat exchanger fabrication methods such as brazing are labour intensive and limit post-processing operations like welding. In this paper, a novel micro-heat exchanger fabrication method using recently patented technologies is presented. The approach uses thermal spray processes such as Pulsed Gas Dynamic Spraying (PGDS) as an alternative to brazing for the production of a pressure barrier and integration of flow headers. Mesh wafer surfaces sealed using PGDS

Concentrating solar power (CSP) systems represent a zero emission method for conversion of sunlight to electricity. CSP systems use an array of mirrors to concentrate sunlight on the surface of a heat exchanger and heat a working fluid. These heat exchanger surfaces must have high absorptivity and low emissivity in the solar spectrum. In addition, they must be capable of extended operation at temperatures in excess of 600°C. Initial development of solar selective coatings using the air plasma spray process will be discussed. Eight different coating materials were deposited onto 304L stainless steel substrates. Solar absorptance and emittance were measured from each coating in three conditions: as-deposited, after heat treatment at 600°C for six hours, and after polishing to a 1 µm finish. A figure of merit based upon solar power tower (SPT) operation was calculated from these data and compared to the industry standard solar selective coating for SPT receivers, Pyromark Series 2500 high temperature paint. This comparison shows that Ni-5Al, 80WC-20Co, and CeO plasma-sprayed coatings all have potential as solar selective surfaces for SPT receivers.

Thermal spray coating processes have been employed in the current study to deposit well-adhered, dense skins on the surfaces of open-cell nickel foams. Using foam with 10 and 40 PPI (pores per inch) pore sizes, square channels were made with a height of 20mm and having a length of 250mm. In a unique process that prevents the deposited skin from penetrating the foam substrate via a paste comprised of a thermoset resin and powder particles, a dense stainless steel skin with an average thickness of 400 μm is applied to the exterior of the foam sample. The result is a channel that consists of a Ni foam core and a stainless steel skin wall that can be used as a compact heat-exchanger by directing the coolant flow through the foam. To study the feasibility of the metallic foam heat-exchangers, hydraulic and heat-transfer characteristics were investigated experimentally. The local wall and fluid temperature distribution and the pressure drop along the length of the heat exchanger were measured for heat-flux of 1540.35 – 9627.38 W/m 2 . Experiments were conducted using air as the coolant and varying flow velocity from 10 – 80 L/min. For non-Darcy flow with inertia effects in the porous media, the Dupuit and Forchheimer modification is employed with the experimental results to determine foam characteristics such as permeability (K), Ergun coefficient (CE) and the friction factor (f). To measure the heat-transfer performance of the metal foam filled channels, a length average Nusselt number is derived based on the local wall and fluid temperatures. Heat transfer was shown to have nearly doubled compared to that of a channel without a foam core.

Open pore foams can be used as gas filters, catalyst supports, and heat exchangers due to their high gas permeability and heat conductivity. In this study, Ni-Cr skins were deposited on each side of a foam sheet by HVOF spraying to form a sandwich structure for use as a heat exchanger. The microstructure of the skins and the interface with the nickel foam struts were examined and the hydraulic characteristics and heat transfer properties of the sandwich structure were experimentally determined. Pressure drops across the heat exchanger were measured and found to be proportional to the square of the velocity of the coolant and a least square fit was used to solve for the permeability, K, and form coefficient, C, of the foam.

Abradable seals have been used in jet engines since the late 1960's. Today they are seeing applications in low pressure and high pressure sections of compressors as well as the high pressure turbine module of jet engines. Clearance control systems using abradable coatings are also gaining ever more attention in industrial and steam turbine applications. Thermal spraying is a relatively simple and cost effective means to apply abradable seals. Abradable coatings work by minimizing gaps between rotating and stationary components by allowing the rotating parts to cut into the stationary ones. Typically plasma and combustion spray processes are used for applying abradable coatings. The types of coatings employed in the HP turbine are zirconia based abradable material systems with polymer and, in some cases, solid lubricant additions such as hexagonal boron nitride. The coatings are designed to work at service temperatures of up to 1200°C. Types of matrix materials used in the low and high pressure sections of the compressor are aluminum-silicon, nickel and MCrAlY based systems. These compressor type systems typically also contain fugitive phases of polymer and/or solid lubricants such as hexagonal boron nitride or graphite. Operating temperature, depending on the material of choice, can be up to 750°C. Regardless of the specific application, fugitive phases and porosity are needed for abradable coatings. Polymers are used to create and control porosity in plasma sprayed coatings, a critical design requirement in adjusting abradability and erosion properties of thermal spray coatings. Combustion spray coatings generate porosity through the lower deposition velocities and temperatures compared to plasma and typically do not need polymer phases. Solid lubricants are added to help weaken the structure of thermal spray coatings and reduce frictional heating and material transfer to the blade.

In modern jet engines, the efficiency of the compressor stages is highly dependent on the clearance between blade tip and casing. In order to improve efficiency of gas turbines (i.e. areo engines as well as land based gas turbines), the gap between the rotating turbine blades and casing has to be minimized. Any increase in the gap results in power loss. Abradable coatings permit a minimization of the clearance and control of the over-tip leakage by allowing the blade tips to cut into the coating. Thermal sprayed abradable coatings aim at a well balanced profile of properties relevant for the application as abradable seals. Amongst others these include: abradability, ageing resistance, corrosion and oxidation resistance, surface finish and bond strength to substrate materials. In this work, abradable coatings consisting of a multiphase material, comprising a metal matrix in addition to a solid lubricant as well as a defined level of porosity, were developed using the Triplex Pro 200 (Sulzer Metco, Wohlen, Switzerland) in order to increase the reproducibility and deposition efficiency. Additionally the influence of the process parameters on coating characteristics such as porosity, hardness and, resulting from this, coating erosion properties and abradability was investigated.

Nickel-based superalloys can be used at temperatures up to 1050 °C in air. Superalloy open cell foam sheets with skin layers plasma sprayed on both sides can be used as high temperature heat exchangers provided that the two deposited skins are dense and well adhered to the open cell foam. In this study alloy 625 skins were deposited on each side of a sheet of metal foam by APS and HVOF to form a sandwich structure. Two densities of open cell foams, 20 and 10 pores per linear inch (ppi), were used in this study as the core. The initial Ni foam was converted to an alloy composition by plasma spraying aluminum and chromium on the foam’s struts with subsequent diffusion/solutionizing heat treatments before the alloy 625 skins were deposited. The microstructure of the coatings and the interface between the struts and skins was investigated. A layer of Ni-Al alloy was formed near the surface of the struts as a result of the heat treatment. The foam struts were imbedded more deeply into the coatings deposited by HVOF than the coatings deposited by APS.

The conventional manufacturing process of the automotive brazed heat exchanger includes complex preparation processes before brazing: aluminum brazing filler alloy is pre-claded on both sides of a fin by an extrusion method, and holed aluminum tubes are coated on both sides with Zn for corrosion protection by a wire arc spraying process. The intent of this study is to simplify the preparation process by kinetic spraying using all of the components, including Al-12%Si (for the brazing filler metal), Zn (for corrosion protection), and KAlF4 (flux powder). Four kinds of blended powder, with and without flux, were evaluated. The bond properties and composition distribution at the braze joint area were evaluated by SEM and an electron probe micro analyzer (EPMA). It was necessary to control the Zn content so that the corrosion resistance and brazeability of the aluminum heat exchanger would not be affected. An optimal kinetic spray condition was obtained, in order to fabricate the heat exchanger in this study. It was observed that the joints of the brazed specimens on each side of the brazing part were sounder than those achieved brazed by the conventional methods. Further, the kinetic sprayed heat exchanger showed acceptable corrosion protection.

Fireside corrosion and erosion of heat exchanger tubes is a serious problem. One of the methods to combat this is by applying corrosion and erosion resistant coatings. Nickel– chromium alloys have already been used as coatings to deal with oxidation environments at high temperature. The wear resistance of these coatings can be improved by adding different hard precipitates such as carbides of refractory metals and cemented carbides. In the present study, various compositions comprising of Ni-Cr with 15, 35, 60 and 100% wt% WC/Co were made using thermal spray grade powders. These were then coated on steel substrate by the HVOF method. After detailed characterization of the coatings, the performance of the coatings at high temperature was studied by exposing the coated samples in the temperature range of 600-700°C. Ni-alloy coatings with moderately (15%) added WC/Co showed better oxidation resistance than coatings with high percentage of WC/Co and also than the pure Ni-alloy coating in high temperature range of 600-800°C. From the characterization, it was found that Ni-Cr alloy with 15% WC/Co gave the optimum results.

In modern jet engines, the efficiency of the compressor stages is highly dependent upon the clearance between housing and rotating compressor blades. To control the over-tip leakage, abradable coating systems are applied on the housing. In the high pressure compressor they typically consist of a thermal sprayed multiphase material, comprising a metal matrix combined with a dislocator and/or a solid lubricant as well as a defined level of porosity. In this study, novel material systems have been sprayed via the plasma and flame spray process and compared to reference materials. Resulting microstructures have been analyzed as well as important coating characteristics evaluated, including coating hardness and erosion resistance. Furthermore rig tests were performed to analyse the coatings abradability behaviour under different operation conditions of the compressor.

The balanced flow type condenser is one of important part used in the air-conditioner of automobile. The manufacture needs the surface of aluminum multi-void to be coated with zinc. One of economical and efficient process is the automatic wire arc spray, in which the maintain of temperature and the in-process speed can make key effects on the quality of coatings. The relation between substrate temperature and the composition, structure and corrosion resistance of the coating of aluminum multi-void are mainly discussed to confirm the best in-process speed of aluminum multi-void, the maintain of temperature and the parameters of arc spraying. Abstract only; no full-text paper available.

Pb-Sn alloys tend to form string-like abrasion products during compressor operations, and the products cause malfunctions at the down streams of the seals and may affect the operation efficiency of the compressors. In this article, a thermal spraying method is developed for forming an abradable labyrinth seal of powdered abradable alloys to cope with the problems for improving the product quality and the operation life of the compressors. The article evaluates the abradable properties of the thermal sprayed coating labyrinth seals of the RIK-type compressors that have higher rotational speed than the other type. Various abradable properties of the sprayed coating are tested by the following test methods: microstructure observation, bond strength, machinability, bending ductility, and corrosion resistance. The article reports the results obtained from these test methods and compares them with those of the cast alloy.

This paper discusses the gases used in different thermal spraying processes and the factors that determine purity requirements, consumption rates, and working temperature and pressure. It explains how process gases are supplied to and distributed within manufacturing facilities and how gas-handling systems and related equipment are tested for operational suitability and safety. Paper includes a German-language abstract.

The ASM Thermal Spray Society Recommended Practices Committee, through its Subcommittee on Safety, is responsible for the development and dissemination of practical recommendations for thermal spraying work. This paper discusses the guidance set forth in the “Recommended Practice for the Handling and Usage of Gases in Thermal Spraying,” which deals with the installation, operation, and maintenance of gas equipment used in spraying processes. It summarizes the hazards associated with compressed gases and high-pressure cylinders and presents precautionary measures to reduce the risks. Paper includes a German-language abstract.