Previous own works revealed that novel partially amorphous Fe-based alloys have a combination of proper-ties that are beneficial for the application in liquid hydrogen (LH2) tanks, viz low thermal diffusivity, little porosity, and good adhesion. The influence of cryogenic temperatures or hydrogen on coating tensile strength, on the other hand, has not been investigated yet for this material. However, this is crucial for the long-term durability of the coatings under hydrogen and other alternative fuels. Thus, in this work, tubular coating tensile (TCT) tests were performed at room temperature and cryogenic temperatures. In addition, hydrogen charging was carried out to identify a possible regime that is sufficient for TCT tests under the influence of hydrogen. Subsequently, the fracture surfaces were evaluated analytically, optically and profilometrically. Under cryogenic conditions, a significant increase in tensile strength and a finer structure of the fracture surfaces was observed.

The amorphous Fe-based coating was fabricated on 304 stainless steel matrix by high velocity oxygen fuel (HVOF). The microstructure, friction properties and wear mechanism of the coating were mainly analyzed by scanning electron microscopy, X-ray diffractometer, Vickers microhardness tester, friction and wear tester, three-dimensional optical profilometer. Results show that: most of the coatings were amorphous, and the amorphous content increased first and then decreased with the increase of heat input. When the spraying parameters are kerosene flow rate 21 L/h, oxygen flow rate 56 m 3 /h, powder feeding rate 35 g/min, spraying distance 360 mm, the coating amorphous content is up to 84%, the hardness is over 842 HV 0.2 , the wear resistance advances over 2.9 times than the matrix.

In this paper, the principles of computational fluid dynamics are used to simulate the complex gas flows in the cylinder bore of an automotive engine during internal-diameter twin-wire arc spraying. A number of experiments are conducted as well and the results are presented and analyzed in order to optimize the properties of the coating. The combination of simulation and experiments led to the development of a process that achieves uniform layer adhesion strength over the length of the cylinder bore.

Nowadays combustion engines are the most common way to impel vehicles. Thereby losses occur, due to cooling, exhaust gas and friction. Modern engines roughly dissipate 8% of the chemical energy stored in the fuel because of friction in different tribological systems. The highest potentials for optimisation can be found in the tribological system of inner surface of combustion chamber and piston ring. Besides friction, corrosive stress of inner surface of combustion chamber increases e.g. due to the utilization of auxiliary systems such as Exhaust-Gas-Recovery. In order to save energy, reduce emissions and enhance the lifetime of combustion engines innovative coating material systems need to be developed, especially for inner surface of combustion chamber. This study focuses on the development of innovative iron based materials for combustion chamber application using Plasma Transferred Wire Arc (PTWA) and Rotating Single Wire Arc (RSW) technologies. In order to improve the wear and corrosion resistance boron and chromium are added into the feedstock material. After deposition, different honing topographies are manufactured in order to evaluate their influence on the tribological behavior. Furthermore, electro-chemical corrosion tests are conducted by using an electrolyte simulating the exhaust gas concentrate. In conclusion an optimised coating material deposited by PTWA and RSW and improved surface topographies can be combined.

The lower wear and poor impact resistance of the amorphous coatings has been a great problem in the past few years for their use in industrial applications. Several research methods have been reported recently to overcome this issue. The present paper addresses the main work done recently on iron based amorphous composite coatings by the addition of 0-20% Alumina particles. These particles were homogeneously distributed in the amorphous matrix of the coatings which improved wear and impact resistance as compared to the monolithic coatings without any decrease in corrosion resistance. The hard alumina particles enhanced wear resistance to several times not only in air but also in salt water solution with a decrease in friction coefficient. The combined effect of wear and corrosion were also observed to become better by the alumina addition. Furthermore, the impact resistance was also improved three times by the addition of alumina particles. The hard second phase particles present in the amorphous coating matrix disperses the residual stresses generated during the impact loading. The brittle alumina particles absorb the impact energy by breaking itself which stop the initiation of cracks and also play a vital role in the crack arresting and blocking of the crack propagation.

Amorphous coatings, despite their high strength and hardness and outstanding corrosion and wear properties, have been limited in application due to poor bonding strength and low impact resistance. This paper reviews the progress that has been made in that regard through the addition of ductile metals, ceramic particles, and polymer phases and through laminar structure design consisting of alternating amorphous and NiCrAl layers. Test results show that the composite amorphous coatings realized by the various methods exhibit significantly improved bonding strength and impact resistance along with their other superior properties.

This study assesses the influence of alumina particle additions on the impact and wear behavior of iron based amorphous coatings. Test results show that the presence of Al 2 O 3 particles improved the impact and wear resistance of the coatings by a factor of three. Deformation and fracture mechanisms under impact loading were also investigated. It was revealed via SEM analysis and finite element simulations that hard second phase particles in the amorphous coating matrix disperse residual stresses generated during impact loading and that brittle particles absorb impact energy by fracturing, which plays a vital role in crack prevention and arresting. Abstract only; no full-text paper available.

Thermally sprayed Fe-based coatings reinforced by TiC particles are a cost effective alternative to carbide coatings such as WC/CoCr, Cr 3 C 2 /NiCr and hard chrome coatings. They feature a good wear resistance and, with sufficient amount of alloying elements like Cr and Ni, also a high corrosion resistance. In hydraulic systems the piston is coated for protection against corrosion and wear. New water-based hydraulic fluids require an adaption of the coating system. In order to investigate the wear and corrosion resistance of Fe/TiC a novel powder consisting of a FeCr27Ni18Mo3 matrix and 34 wt.-% TiC was applied by HVOF and compared to reference samples made of WC/CoCr (HVAF) and hard chrome. Besides an in-depth coating characterization (metallographic analyses, EMPA), wear resistance was tested under reverse sliding in a water-based hydraulic fluid. Corrosion resistance was determined by polarization in application-oriented electrolytes (hydraulic fluid at 60 °C, artificial sea water at RT).

This study investigates the effects of feedstock composition and annealing temperature on cold-sprayed aluminum-iron deposits. Commercially available Al and Fe powders mixed in ratios of 55:45, 75:25, and 85:15 were cold sprayed on aluminum substrates, producing dense coatings that were subsequently annealed at 500 and 550 °C. Solid diffusion reactions between Fe and Al produced Al 5 Fe 2 intermetallic compounds, the morphology and content of which were found to depend on annealing temperature and the composition of the as-sprayed deposit. The Fe particles in the Al matrix were fully consumed via compounding reaction with Al at 550 °C. At higher temperatures, however, the intermetallic particles begin to crack possibly due to large tensile stresses.

In the present study, X-ray microtomography is used to examine cold-sprayed tantalum splats on copper substrates. To resolve tantalum splats intermeshed with other splats of the same chemical composition, a contrasting medium of some sort is required. For this purpose, the feedstock powder is coated with an iron layer by means of fluidized-bed chemical vapor deposition. Experimental tests were coupled with finite element simulations to determine how stresses generated during the impact of a spherical iron-coated particle affect the integrity of the added contrasting layer.

In every industry wear plates and parts are demanded in heavy duty standards at cost effectiveness and environmental friendliness. For that reasons a new kind of coating technology was developed, and first applied on parts for agricultural machinery for getting results from the field. Simultaneously lab tests were done to compare the wear behaviour and performance of these sintered iron-based coatings with mainly chromium-carbides and borides in it, with other well known wear-resistant coatings like hard chrome, thermal sprayed coatings (Ni-matrix/WC), PTA welded coatings (Ni-matrix/WC, high speed steel) and processed steel like Hardox. Wear tests were performed under 3-body-abrasion as well as combined impact/abrasion conditions, respectively. Dry-sand rubber-wheel procedure according ASTM G65 was used to investigate low stress abrasion, whereas for high stress abrasion investigations a steel wheel was used. A special designed impeller-tumbler apparatus was used for combined impact and abrasion wear tests. Analysis after testing was done quantitatively by gravimetric mass loss, and qualitatively using SEM microscopy (edge stability, wear mechanisms). The ambition of this investigation is to secure the wear performance of the sintered iron-based coating at low production costs compared to well known anti-wear solutions applied in wear intensive industries.

Thermal spray coatings have been applied on furnace rolls in continuous annealing lines to improve product quality and prolong roll service life. The most common defects formed on working furnace rolls are oxide pickups. In this study, HVOF sprayed cermet coatings are used to duplicate pickups by reacting with iron and manganese oxides. The reactions are performed in a furnace at 900 °C with inert gas flow. After testing for eight days, large Mn-rich pickups were formed on the coatings while pickups without Mn were very small. Mn was shown to enhance the reaction between the coating and the iron oxide. Pickups from a furnace roll were also investigated and compared with the laboratory samples.

Due to its easy handling and low operating costs, wire arc spraying has become one of the most established processes for applying protective coatings to components used in waste incineration plants. This paper discusses the development of relatively low-cost Fe-Cr-Si coating materials for incinerator applications and the corrosion and wear properties that have been achieved using conventional arc spraying methods.

Iron-based wire feedstocks represent a technical as well as economical alternative to carbide reinforced feedstocks for wear protection applications. To assess the potential of such feedstocks, iron-based cored wires were developed with up to 6 wt% boron. The feedstocks were deposited by electric arc spraying, forming hard, partially amorphous coatings with embedded nanocrystalline boride precipitations. To further improve wear resistance, chromium carbide was blended into the powder filling in some wires. Coatings produced from all feedstocks were evaluated by means of optical microscopy, X-ray diffraction, and microhardness measurements.

The objective of this work is the development and application of Fe-based wear- and corrosion-resistant coatings with uniform density and even coating surfaces. The coatings obtained were analyzed with respect to microstructure, hardness, and surface roughness.

Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. As commercial arc sprayed coatings have been used to a limited extent in applications involving erosion and abrasion wear, developing attractive wear resistance arc sprayed coatings has been found necessary. Abrasive wear testing was carried out on four Fe-based composite coatings containing varied contents of Cr 3 C 2 particles as hard phases. Scanning electron microscopy (SEM) was used for observing the surfaces of the composite coatings, and wear mechanisms of the coatings were discussed on the basis of the observation. The results obtained from MLS- 225 wet sand/rubber wheel test showed that the abrasive wear resistance of composite coatings with Cr 3 C 2 hard phase is about 28 times higher than that of Q235 mild steel. The coating method was proved effective in producing a uniform and dense lamellar structure. The excellent abrasive resistance of the composite coatings with Cr 3 C 2 particles were found to be related to three major factors: enhanced bulk hardness, compact lamellar structure and strong bonding between matrix and hard phase, as well as a load supporting system constructed by the hard phase structure.

Iron base composite coatings were deposited on mild steel substrates by arc spraying and cored wire with TiC ceramic powders. The abrasive wear resistance properties were examined on the MLS-225 wet sand/rubber wheel tester. The microstructure, phase compositions and worn surface morphologies of the coatings were observed by means of optical, scanning electron microscopy and X-ray diffraction. The results showed that composite coatings with TiC ceramic hard phases were reinforced by the TiC hard particles distributed in the iron-based coating. The average micro hardness of the coatings is about 1137 HV0.1. The coatings have the excellent abrasive wear resistance which is 6 times higher than that of the Q235 mild steel. Wear mechanisms of coatings was mainly micro-ploughing and brittle fracture.

It is widely held that most of the oxidation in thermally sprayed coatings occurs on the surface of the droplet after it has flattened. The evidence in this paper suggests that, for the conditions studied here, oxidation of the top surface of flattened droplets is not the dominant oxidation mechanism. In this study, a mild steel wire (AISI 1025) was sprayed using a high-velocity oxy-fuel (HVOF) torch onto copper and aluminum substrates. Ion milling and Auger spectroscopy were used to examine the distribution of oxides within individual splats. Conventional metallographic analysis was also used to study oxide distributions within coatings that were sprayed under the same conditions. An analytical model for oxidation of the exposed surface of a splat is presented. Based on literature data, the model assumes that diffusion of iron through a solid FeO layer is the rate limiting factor in forming the oxide on the top surface of a splat. An FeO layer only a few thousandths of a micron thick is predicted to form on the splat surface as it cools. However, the experimental evidence shows that the oxide layers are typically 100x thicker than the predicted value. These thick, oxide layers are not always observed on the top surface of a splat. Indeed, in some instances the oxide layer is on the bottom, and the metal is on the top. The observed oxide distributions are more consistently explained if most of the oxide formed before the droplets impact the substrate.