Thermally sprayed heating coatings are a recent approach for temperature control in moulding tools. While there are material options in the lower temperature range up to T = 300 °C, new alloys have to be developed to improve the range of application. The Al 0.5 CoCrFeNi high-entropy alloy (HEA) with further addition of Zr and Si shows favourable electrical properties due to severe lattice distortion. The alloy development was carried out with Al 0.5 CoCrFeNiZr x Si y by arc melting. Thereby, the molar Zr content x was varied from 0 to 0.5 and the Si content y from 0 to 0.2. In order to evaluate the alloy’s prospective performance, the phase composition was studied by SEM with EDX and the fracture toughness was determined to estimate fracture properties, which are found to be a typical failure mechanism of heating coatings. The different HEA exhibit a typical dendritic microstructure with fcc dendrites and a bcc interdentritic phase. The hardness of the alloys increases with increasing bcc content, while the ductility decreases. With knowledge about the effects of Zr and Si on the electrical and mechanical properties, which are justified by the microstructure, Al 0.5 CoCrFeNiZr x Si y HEA can be tailored specifically towards the needs of individual heating applications.

The quality of feedstock powder is a critical factor in determining the properties of coatings deposited using cold spray (CS). However, most commercially available powders are not designed or optimized for CS applications, making it challenging to tailor powders to desired quality. In this research, we investigated and compared the cold-sprayability of four different Cu powders produced by electrolysis and gasatomization methods. We assessed the powders' microstructure, particle morphology and size distribution to understand the effect of manufacturing methods on Cu powder characteristics. We also studied the flowability of the powders using the shear cell method and evaluated their mechanical properties and deformability for CS using nano-indentation. Our results showed that gas-atomized powders with equiaxed grains exhibited promising flowability and deformability for CS applications, outperforming the other powders tested. Specifically, the spherical morphology of gas-atomized powders provided less surface area than the irregular-shaped electrolytic powder, reducing the interaction of surface forces and contributing to smooth powder flow. Additionally, the gasatomized powder with small dendrites in the microstructure exhibited the highest nano-hardness value (HIT= 1.6±0.1 GPa), while the porous electrolytic Cu powder had the lowest value (HIT= 0.7±0.2 GPa). In conclusion, we found that gas-atomized Cu powders with equiaxed grains may hold promise as the optimised feedstock for CS application, considering both effective metrics of flowability and deformability.

Material’s tensile strength can be improved by the presence of a body-centered cubic (BCC) phase, which is essential in highstrength applications and highly corrosive environments. Thus, synthesizing a BCC single-phase, equiatomic AlCoCrFeNi high-entropy alloy (HEA) feedstock particle using a highenergy mechanical alloying (HE-MA) method was investigated. The transient alloy particles were developed using a planetary mill at a constant rotational speed of 580 rpm employing milling times in the range of 4 to 24 hours. During the process, stearic acid of 3 wt.% of the precursor composition was used as a process-controlling agent (PCA). Two HE-MA manufacturing regimes were utilized: i) conventional (milling constituent elements simultaneously), and ii) sequential (progressive milling while adding elements in a certain order). In addition to the conventional method, a sequential regime was employed to develop FeNiCoCrAl, wherein individual elements were added every 4 hours to the starting/milled Fe + Ni mixture. Based on the results, the HE-MA FeNiCoCrAl showed a BCC single-phase formation after 24 hours, with no intermetallic or contamination traceability. Finally, a nanoindentation hardness measurement was carried out to support the observed phase transformation before and after the HE-MA process.

This research presents a novel approach for producing metal matrix composite powders using a nanoparticle decoration technique. A 1wt% stable suspension of 30nm Al 2 O 3 particles was decorated onto primary AA6061using a redispersion method. The resulting AA6061-1wt% Al 2 O 3 composite powder was mixed in a rotary mixer for one hour and subsequently dried at 45°C. Scanning electron microscopy of the composite powder confirmed the successful material composition. The composite powders were then deposited onto an AA6061 substrate using a low-pressure cold spray system, with the coating quality, deposition efficiency, surface roughness, and hardness of the deposited materials analyzed. After heat treatment at 430oC, the role of the nanoparticles in hindering recrystallization was studied, with Orowan strengthening shown to be the main mechanism for preventing recrystallization and grain growth. This technique provides a promising alternative method for producing metal matrix composites and offers potential for further exploration of their properties and applications.

The study of self-lubricant coatings is a rapidly developing research field that is expected to address major issues arising from operation under high loads and thermal stresses of machine parts. It is of utmost importance that various critical tribological pairs such as crankshaft bearings, piston rings, etc. maintain their integrity, thus contributing to the engines efficient and reliable operation for long periods of time. Therefore, a choice of high-strength metals is required, with special treatments and/or coatings in combination with sufficient lubrication. In the present study, liquid lubricants encapsulated in poly(urea-formaldehyde) were incorporated in ceramic-metal matrices for the production of composite coatings by Atmospheric Plasma Spraying. Aspects concerning the survival of the capsules during their flight through the high temperature plasma flame, the maintenance of their integrity at impact with the substrate with high kinetic energy, their homogeneous dispersion within the coating mass, thermal spray deposition parameters adjustment and optimization are thoroughly discussed. Coating properties such as roughness, friction, adhesion strength, and wear behaviour were also investigated. Microstructural characteristics and friction-wear behaviour were found to be critical to the durability of coating.

Hardmetal coating compositions containing both WC and Cr 3 C 2 are less intensively studied than WC-Co(Cr) and Cr 3 C 2 -NiCr. In particular, compositions with Cr 3 C 2 as the main phase are relatively new in the market. In this contribution, two commercial agglomerated and sintered feedstock powders with similar compositions (42Cr 3 C 2 -42WC-16Ni and 45Cr 3 C 2 - 37WC-18NiCoCr) were studied. Both powders differ in their porosity and the melting behavior, as was found by DSC experiments. Coatings were deposited with a liquid-fueled HVOF process (JP 5220). Optimization of the spray conditions was evaluated with five different spray parameter sets. Coating microstructures and phase compositions, as well as microhardness HV 0.3 and abrasion wear resistance were less influenced by the spray parameter sets. At the same time, significant differences in deposition efficiency between the two compositions were observed, which might be related to the differences in the melting behavior of the compositions and the powder porosity. However, coating microhardness and abrasion wear resistance were similar for each of the spray parameter sets. Coating microstructure and phase composition were studied with a focus on the interaction between Cr 3 C 2 and WC and will be discussed in detail.