In this work, two different Ni-base powders, namely, ProXon 21021 (P21) and ProXon 21031 (P31), were sprayed onto a steel substrate 35CrMo4 using a thermal flame spray technique. The morphology and chemical composition of the phases that are present in the powders and coatings were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The hardness and wear resistance of the coatings were investigated. The XRD analysis revealed that the phases present in the coatings are different from the initial powders. In addition, some inhomogeneities such as oxides, porosity, and unmelted particles were observed by SEM. It was found that the P31 spray-coated exhibited higher microhardness, higher wear resistance, and significantly lower friction coefficient in comparison with those of P21 coatings.The use of coatings is one of the most effective strategies to protect materials against corrosion and to increase the wear resistance of materials. This allows for developing components with optimized surface behavior using cheaper or more processable materials, like mild carbon steel. Different coating alternatives of carbon steel can be found in the literature: stainless steel, [1,2] 100Cr6 steel, [3,4] Mo, [5,6] organic coatings, [7,8] ceramic coatings, [9,10] and WC-Co. [11,12] Thermal spray is a technique that produces a wide range of these coatings for diverse applications. The principle of thermal spray is to melt material feedstock (wire or powder) to accelerate the melt to impact on a substrate where rapid solidification and deposit build-up occurs. [13] Thermal spraying uses two principal energy sources, chemical energy of the combusting gases that power the flame spray torches (e.g., high velocity oxygen fuel (HVOF) spraying) and electric currents providing energy for the plasmatons (e.g., atmospheric plasma spraying (APS)). All these techniques allow for the deposition of coating on materials generally ductile to improve their corrosion and wear resistance. Nevertheless, more traditional electric arc wire spray and combustion flame spray are still widely used. [14][15][16][17] The flame spray deposition technique has several disadvantages compared with the HVOF or APS methods, including a bigger grain size microstructure, pore size, and crack length, but it also has certain advantages, such as its being more economical, easier to handle, and more adaptable to the manufacturing process with a short series or recovery of pieces. Flame spray was the first thermal spray process developed. Modern torches have changed, and the high particle velocities are in the range of 200-300 m/s. Oxyacetylene torches are using acetylene as the main fuel in combination with oxygen to generate high combustion temperatures and particle temperatures around 2873 K (2600°C). [13] In recent years, thermally sprayed nickel-based alloys are used in a variety of applications, e.g., as bond coats for thermal barrier coatings on turbine components, as restorative layers for mach...
