This study investigates the wear resistance of WC-FeCSiMn coatings deposited on 3D surfaces by two-wire arc spraying. Wear behavior was evaluated by means of pin-on-disc testing, pin-on-rotating tube testing, and a method in which a robot arm moves a pin over test specimens with arbitrary surface geometries. Residual stresses were determined by incremental hole drilling and were found to have a dependency on substrate geometry. After wear testing, a 3D profilometer determined wear volume and coating surfaces were examined by SEM. The results indicate that wear resistance is strongly influenced by the geometry of the substrate.

In this work, plasma spray-physical vapor deposition (PS-PVD) is used to create oxygen transport membranes, consisting of gastight LaSrCoFeO thin films on porous MCrAlY metallic supports. During spraying, a protective layer of alumina forms at the interface between the membrane and support preventing interdiffusion. Surface roughness of the metallic support is shown to play a critical role in limiting microstructural defects. Phase composition, growth rate, and microstructure buildup are also investigated along with the annealing behavior of LSCF films at different temperatures. Initial results are promising and further improvements are expected by optimizing process parameters.

This study analyzes the mechanical properties of aluminum alloy substrates, in particular, changes in flexural behavior of laser-textured surfaces. Bending tests are conducted on samples treated by laser texturing and by conventional methods such as chemical degreasing and sandblasting. A comparison of flexural strengths caused by the different surface pre-treatments method is presented.

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.

This work evaluates the tribological properties of conventional and nanostructured Al 2 O 3 -13TiO 2 coatings obtained by atmospheric plasma spraying. The structure and composition of the composite coatings and powders were analyzed by SEM, TEM, and x-ray diffraction. Nanoindentation and ball-on-disc tests were conducted and surface topography was examined by noncontact 3D profiling. Coating samples of both types were polished and their friction coefficients were measured. The coefficient of friction for nanostructured coatings was 0.51, while that of conventional coatings was 0.62.

This work investigates the reliability and reproducibility of scratch testing for YSZ and TiO 2 coatings deposited on NiCr bondcoats by plasma spraying. Scratch tests were conducted on cross-sections of the spray coatings. An image of the scratched area was taken after testing using an optical microscope in order to determine failure mode. With a statistical evaluation, the adhesion and cohesion strength were determined. The results show that cross-sectional scratch testing is effective for estimating the adhesion and cohesion strength of plasma spray coatings.

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.

Cold spraying is a promising candidate for the metallization of carbon fiber reinforced polymer (CFRP) composites, but it requires the use of a protective interlayer deposited by either flame or plasma spray. This study evaluates the effect of different surface treatments on interlayer adhesion strength. CFRP samples were treated mechanically, chemically, and thermally and then a copper layer was deposited by atmospheric plasma spraying. Adhesion strength was measured by pullout testing and the results are compared with surface roughness measurements, SEM fracture surface images, FIB bisections of single Cu splats, and XPS analysis of the chemical affinity between the polymer and copper.

This study investigates the potential of external powder injection for producing functionally graded coatings by twin wire arc spraying. In spray trials, the position of the injection port was altered along the spray axis and perpendicular to the arc and different powders and carrier gases were used. Real-time images were captured by a high-speed camera during spraying to detect correlations between gas flow rates, hard particle wetting, and atomization of the molten pool. The optimal location for injection was found to be dependent on the size and density of the powder and the flow rate of the carrier gas. In the case of embedding B 4 C in a Fe-based matrix, a strong metallurgical bond was formed, confirming that powder injection is a viable approach for controlling the composition of twin wire arc sprayed coatings.

This study compares the effects of plasma nitriding and nitrocarburizing treatments on HVOF sprayed stainless steel coatings with different crystal structure. The treatments were conducted at 550 °C for 10 h in a gas mixture of N 2 and H 2 for nitriding and N 2 , H 2 , and C 2 H 2 for nitrocarburizing. Optical microscopy, SEM-EDS, and XRD show that the treatments produced thick nitride layers consisting of a compound layer and a nitrogen diffusion layer. The treatments increased not only the surface hardness, but also the load bearing capacity of the coatings due to the formation of CrN, Fe 3 N, and Fe 4 N phases. Plasma nitrocarburized 410 stainless steel had the highest microhardness and load bearing capacity because of the precipitation of Cr 23 C 6 on the surface.

This study ranks a number of common thermal surfacing materials for soil tillage applications based on the results of dry-sand rubber-wheel testing for abrasion resistance. Test specimens were prepared by plasma transferred arc (PTA) and powder welding deposition of a nickel-based self-fluxing matrix with and without tungsten carbide (WC) additions. For comparison, PTA coated M2 tool steel and quenched and tempered spring steels were also tested. PTA and PW deposition produced coatings with a similar level of abrasive wear resistance. Hardfacing with M2 and nickel-based 1560 deposited by PTA showed ~30% and ~15% wear respectively compared to the reference steels, while nickel-based grades with additions of 50% carbide showed only ~5% wear. Moreover, by increasing the amount of WC from 50 to 60 wt%, abrasive wear resistance was increased by 25%.

In this study, iron-based coatings are deposited on stainless steel substrates by HVOF and HVAF spraying and are evaluated based on SEM examination, hardness measurements, and corrosion and wear testing and by comparison with WC-CoCr and CrC-NiCr reference coatings. The results indicate that corrosion resistance is insufficient if the coating is not fully dense and has open porosity. During spraying, the particles must be totally melted and rapidly solidified to achieve uniform coating composition. Open porosity and nonuniform distribution of alloy elements, particularly chromium, is seen to induce crevice corrosion in iron-based coatings.

To answer current issues adequately considering technical, economic, as well as environmental requirements, material transformation and especially surface treatment industries must be source of innovations to be proactive. As a result, developing new alternative solutions to existing ones had become a top priority. Considering surface treatment processes, conventional ones (thermal spraying, plasma transferred arc) do not allow to consider this approach since the processes themselves (co-treatment of different powders) do not permit to guarantee the initial composition nor do they ensure a sufficient homogeneity to the coating structure. If indeed the dry surface treatment processes have already shown large potential, several limits remain such as an inefficient adhesion, an environmental impact over the life cycle or almost no materials on the market. To overcome these issues hybrid coating technologies (combining several processes) are likely to be developed. From all of them, laser technology seems to be very promising due to its high flexibility considering all the potential parameters (varying power, continuous or pulsed beam, etc.) and the localised treated area. For instance, combining simultaneously a laser with a thermal spray process enables the elaboration of a thick coating showing a good adherence. The ablation laser applied on the substrate surface just before the impacting particles as promoted in the PROTAL process permit to insure a suitable surface state favourable to the particles adhesion. The control of the coating microstructure was not so much studied. That is why, to complete the knowledge in this area, this work aims at studying the influence of laser technology in association with plasma spraying on the coating microstructure and more precisely on the coating mechanical properties. Coatings were characterized by SEM and void content was evaluated through image analysis and Archimedean porosimetry. Mechanical properties were assessed by the four points bending test for evaluating the coating apparent Young modulus.

Magnesium and magnesium alloys are the lightest structural materials with an approximate density of 1.7 g/cm³ (density of aluminium ~2.7 g/cm³). Due to the poor corrosion and wear resistance properties, they need to be coated for usage in lightweight constructions. AlSi20 was found to be a suitable coating material to improve the properties of parts made of the magnesium alloy AZ31B. Within this work, coatings are applied by thermal spraying, laser cladding and the combination of both processes. These coatings were investigated regarding corrosion protection in 3.5 % chlorine solution in a three electrode setup to obtain electrochemical corrosion characteristics. Abrasive wear was investigated using a pin-on-disc tribometer and abrasion rate was calculated. Resistance against shock loads was tested by applying a cyclic load at 50 Hz in order to investigate the resistance against impact stresses.

Functionally graded coatings exhibit outstanding thermomechanical performances that meet economic demands. By influencing the microstructural formation of the layers of the coated tool, the distribution and transfer of heat from the impact zone into the forming process is determined. Thus, largely affects the tool’s life cycle and microstructure in the surface area of the parts to be formed. With respect to graded coatings, examinations on simple substrates have already shown the applicability of different microstructure formations of coatings. In these approaches, varied parameter settings were investigated to identify the most significant factors and their effects on the formation of the microstructure. Furthermore, using different grain-sized powder materials and utilizing other thermal spraying methods, it is possible to generate either porous or dense coatings according to their requirement profile. The utilization of different thermal spray methods particularly leads to high costs caused by increased setup times. As opposed to traditional thermal spray deposition process parameters for graded coatings, generated by an in-situ process, need to become coordinated with the movements of the robot. In this study, we investigated the dependencies between the spray parameters of Atmospheric Plasma Spraying, such as spray distance and spray angle, and the formation of microstructures. The investigation focusses on the utilization of Alumina (Al 2 O 3 ) which is widely used as a wear and corrosion resistant coating.

Coatings, a few-millimeter thick, are widely used to protect new mechanical parts against abrasion and erosion or rebuild worn parts. The plasma transferred arc process is a commonly used process to deposit such coatings. It makes it possible to bring about a metal bath inside which melted powders are introduced to form an alloyed coating between the feedstock material and substrate material with metallurgical adhesion. The main parameters of the process are the arc current intensity, plasma and shrouding gas flow rates, distance between the cathode tip and piece, velocity of plasma torch displacement; they all have a notable effect on the produced coating. This study investigates the plasma behavior and properties of the clad by using a design of experiments. The properties of the coating are the dilution level, porosity, and efficiency of material deposition, heat flux transferred to a water-cooled calorimeter, and the hardness in the clad and the substrate to estimate the thermally affected area.

Earlier works have demonstrated that Fe2B-based arc-sprayed coatings and weld overlays present outstanding dry erosion resistance when compared to other carbide-based coatings and overlays. The present work was undertaken to examine their wear resistance, particularly their slurry erosion resistance. Cored wires containing chromium (2-20 wt%) and carbon (0.2-1.2 wt%) additives were deposited by arc spraying and gas metal arc welding (GMAW). The abrasion, particle erosion and slurry erosion resistances of these (Fe-B-Cr-C) coatings and overlays were evaluated in laboratory. The results demonstrate that both differences in cored wire composition and variations in the deposition process must be considered in order to obtain the best wear properties.