This study developed microstructure-based finite element (FE) models to investigate the behavior of cold-sprayed aluminum-alumina (Al-Al2O3) metal matrix composite (MMCs) coatings subject to indentation and quasi-static compression. Based on microstructural features (i.e., particle weight fraction, particle size, and porosity) of the MMC coatings, representative volume elements (RVEs) were generated by using Digimat software and then imported into ABAQUS/Explicit. State-of-the-art physics-based modelling approaches were incorporated into the model to account for particle cracking, interface debonding, and ductile failure of the matrix. This allowed for analysis and informing on the deformation and failure responses. The model was validated with experimental results for cold-sprayed Al-18 wt.% Al2O3, Al-34 wt.% Al2O3, and Al-46 wt.% Al2O3 metal matrix composite coatings under quasi-static compression by comparing the stress versus strain histories and observed failure mechanisms (e.g., matrix ductile failure). The results showed that the computational framework is able to capture the response of this cold-sprayed material system under compression and indentation, both qualitatively and quantitatively. The outcomes of this work have implications for extending the model to materials design and under different types of loading (e.g., erosion and fatigue).

In this work, tungsten carbide coatings are deposited by low-pressure cold spraying in order to assess the influence of powder compressive strength and binder materials on coating properties. Powder compressive strength was measured with a micro-compression tester, and cobalt and FeCr in different proportions were used as the metal binder. It was found that compressive strength affects coating hardness as well as deposition efficiency and that the optimum value for deposition efficiency is about 200 MPa. The results also indicate that dense coatings can be produced with either binder material, although coatings with an FeCr binder are the hardest.

In cold spray, feedstock powders are accelerated by supersonic jet with solid phase and deposited onto substrate. Compare with the conventional thermal spray, the coatings have low porosity without oxidation and decomposition. This study examines the effect of the powder compressive strength of each particle on coating deposition characteristics using two types of Ni powders, manufactured in a different process, in cold spray. The result indicated that heat treatment reduced the powder compressive strength, and the decrease of the powder compressive strength was related to the increase of bond strength of particles and deposition efficiency. In addition, it was shown that the powder compressive strength has an influence of deposition mechanism.

The quality and operation performance of layer composites manufactured by thermal spraying is influenced by two different processes, the activation process of the surface prior to coating deposition and the coating process itself. The activation of the substrate surface is mainly performed by grit blasting operations. Surface activation by grit blasting is used in order to improve the bonding between substrate and coating, which is strongly related to the size and nature of the surface topography and roughness generated by the blasting process. Besides the roughening effect, grit blasting induces compressive residual stresses into the substrate surface which can be critical especially for thin walled components, e.g. piston rings, where the component shape is an important factor for the operation behavior and functionality. Another effect is an increase of hardness in the surface region related to the induced compressive stresses. A variety of blasting parameters can influence the surface characteristics, like nozzle diameter, grit medium and size, blasting pressure, distance and time. The influence of these parameters on the surface roughness, hardness, component deformation and residual stresses was investigated by tactile surface metrology, universal hardness and Almen tests as well as experimental residual stress analysis with the incremental hole drilling and milling method. All investigations were performed on rectangular steel strips. The results are discussed concerning quality control features for grit blasting processes in serial production.

This paper aims to fabricate wear resistant composite coatings on light metal substrates which also exhibit low friction coefficients. It demonstrates that combined ceramic polymer coating systems are a powerful concept for industrial applications where high wear resistance, creep resistance and compressive strength as well as low friction coefficients are required. The results show that, under the specific experimental conditions used, the titanium dioxide layer in connection with the applied lubricant lacquer showed better performance than the mixed aluminum oxide/titanium dioxide layers. Paper includes a German-language abstract.

This paper describes some of the problems solved in the development of a mold-making process in which the molds are coated using a 2mm wire arc-spraying system. A water solution release agent has been chosen to meet industry standards and requirements. The composition of backup materials was chosen based on compression strength testing. The material selected has high ultimate compression strength and high thermal conductivity and can be readily incorporated in the mold-making process.

The mechanical properties of plasma sprayed metals and alloys are important in most applications. It a posttreatment by forming of plasma deposited coatings is required, their response to compressive loading is decisive. This paper is concerned with the compressive behaviour of two high-alloy steels sprayed by a water stabilized plasma gun. Martensitic (13.2 % Cr) and austenitic (19.6 % Cr, 11.6 % Ni) steels were plasma sprayed onto plain steel substrates. Small cube-shaped test samples were cut out of thick coatings by an electrospark technique. Compressive load was applied along axes parallel and perpendicular to the substrate and coating surfaces. In addition, comparative samples of bulk steels produced by conventional metallurgy were tested. The compressive behaviour of the as-sprayed martensitic steel was anisotropic at room temperature, i.e. dependent on the orientation of the compression axis. As a result of compression, the splat shapes changed in a manner depending on the orientation of the compression axis. The room temperature compression tests showed that the yield stress of this steel was decreased and the anisotropy was reduced by annealing after plasma spraying. At room temperature, the anisotropy of the as-sprayed austenitic steel and the effect of annealing were less pronounced in comparison with the martensitic steel. Very low values of the yield stress were observed in both steels compressed at the annealing temperature. In spite of the presence of oxide films enveloping each splat, the coatings were prone to considerable plastic deformation, in particular if compressed along the axis perpendicular to the surface.

Functionally gradient composites were spray formed via vacuum plasma spray deposition using tungsten cylindrical substrates. Materials deposited included tungsten-hafnium alloys and M-2 tool steel. Some deposits included micro-laminate layering with hafiiium alloys sprayed within the tungsten-hafnium matrix. Vacuum plasma deposition was shown to provide a viable means of producing functionally gradient composites from tungsten base materials. This was determined both by microstructural characterization of deposit structures and by measuring the compressive properties of the materials. Compression testing of the W-Hf matrix composites demonstrated compression strength of 1,552 MPa (225 ksi). Compression strengths of the tungsten/steel composite averaged 1,068 MPa (155 ksi). Failure of the W-Hf samples occurred via fracture of the tungsten/hafnium matrix whereas the tungsten/steel composites failed within the wrought tungsten core.