One of the main problems that slows down the implementation of the green hydrogen (H 2 ) economy is the cost of water electrolysis. While part of this cost is associated to the price of electricity, a significant part relies on the parts of the electrolyzers. Despite their advantages, Proton Exchange Membrane Water Electrolyzers (PEMWE) still have to overcome some drawbacks to reduce its H 2 production cost, while maintaining high efficiencies. For decades, thermal spraying has been used for the production of coatings all over the world because of its versatility in industry for machinery and tools preservation, surfaces protection and corrosion prevention. This study demonstrates the possibilities of Cold Gas Spray (CGS) for the cost-reductive production of a component of PEMWEs, the Bipolar Plates (BPPs), by metal 3D printing. In this process, the incorporation of a mask between the nozzle exit and the substrate can drastically transform the BPP production to a very fast and automatic bottom-up process where material is deposited layer by- layer for building up the three-dimensional flow field patterns from a flat surface. Microstructure and topography of 3D printed BPPs were inspected by microscopy techniques. For evaluating the fulfilment of BPPs requirements (interfacial contact resistance and corrosion resistance) the new BPPs were characterized following the Davies’ method and with potentiodynamic test in O 2 -saturated H 2 SO 4 solutions, respectively.

Cold Spraying (CS) is a thermal spray process capable of producing dense and thick coatings by the spraying of powders under high velocity and relatively low temperature. The high deposition efficiency and the thickness of each pass make possible the use of CS to produce freestanding parts, as an additive manufacturing process (CSAM). Traditionally, CS is performed spraying perpendicularly to the substrate, which ensures maximum deposition efficiency among other benefits. This, however, presents two main disadvantages for CSAM. First, by keeping the spraying angle constant, there is not much control on the final geometry of the part being built, and, second, the resultant part’s properties show anisotropy depending on whether this property is measured along the spraying axe or not. In this work, we present a method (Metal Knitting) that aims to help reduce both disadvantages. Metal Knitting is based on the performance of certain spraying movements that build near squared shapes step-by-step like in a knitting process. The principle of the method and examples are presented in this work, as well as some results on the anisotropy of 316L stainless steel freeform parts obtained by CSAM, measuring the tensile stress, hardness, and evaluating the microstructure in different directions of the material. The effect of annealing on the material properties is also investigated.

TiC-based coatings have proven to be very suitable candidates in various areas of thermal spraying when high corrosion and wear resistance is required. The most important advantages of these coatings are their high corrosion resistance compared to conventional coatings such as WC+Co and WC+Co+Cr, but also their low density. However, the main problem with HVOF spraying these materials is their high reactivity with the oxygen necessary for the flame. In this paper, Self-Propagating High-Temperature Synthesis-TiC+Ni-Ti base powder are processed with two different spray guns (Diamond Jet Hybrid (DJH) and CDS 100). This allows to compare the properties of the resultant coatings (wear and corrosion mainly) as a consequence of the main advantages of each variable (gun and gas) particularly in relation to the oxidation processes. It is observed that DJH coatings showed the best corrosion resistance whilst CDS coatings showed a corrosion potential closer to the steel value. Paper includes a German-language abstract.

The development of new spraying processes has increased the demand for high quality protecive coatings. Many thermal spraying processes have been developed to obtain coatings for a wide spectrum of materials and substrates. The High Velocity Oxygen Fuel (HVOF) process involves lower temperatures and higher velocities than those required by other techniques to obtain high density coatings. It is desirable to know which are the main factors that affect the corrosion behaviour of coated materials. The corrosion behaviour in chloride solution of a 34CrMo4 steel coated with different kinds of powder have been studied. The electrochemical corrosion of the coating-substrate system was characterised by corrosion potential measurements and potentiodynamic polarisations. Microscopic studies have also been performed by means of SEM. The corrosion tests were performed in synthetic marine water (ASTM D-1l41) in the presence of dissolved air. Polarisation resistances have been obtained from potentiodynamic studies. Measurements were carried out on two different (Ti,W)C+Ni coatings, as well as on the coatings obtained from a TiC+Ni-Ti powder which had been previously Ni coated using an electro less method. The best corrosion results were obtained from these last coatings.