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Thermally sprayed 316L stainless steel coatings are commonly used on metallic structures due to their corrosion and wear resistance when compared to carbon steel. Cold Gas Spray (CGS) is a convenient thermal spray process to deposit 316L coatings, producing thick and very dense coatings, with almost no deleterious changes on the feedstock properties to the coating condition. The powder characteristics have influence on the microstructure of the coating, such as porosity and oxide contents, which alter its corrosion and wear behavior. CGS is an efficient technique to reduce the problems associated with material melting commonly found in other conventional thermal spray methods. In this work, different 316L powders, produced by different manufacturers, were deposited by CGS, applying the same equipment and parameters, with the objective to evaluate the relation between the powders’ characteristics and coating properties. Their microstructure, adherence, hardness, as well as the performance on corrosion and wear testing were evaluated. The water atomized powders presented in general better results than gas atomized powders.

HVOF thermal spray process produces coatings with low porosity and low oxide content, as well as high substrate adhesion. Small variations on the parameters of the HVOF process can generate coatings with different characteristics and properties, which also is chemical composition depended of the alloy. FeMnCrSi alloy is a cavitation resistant class of material with a great potential for HVOF deposition use. The main goal of this article is to study the influence of some HVOF parameters deposition, as standoff distance, powder feed rate and carrier gas pressure on three different alloys. FeMnCrSi experimental alloys with some variations in nickel and boron content were studied. Taguchi experimental design with L9 orthogonal array was used in this work. Porosity, oxide content, tensile adhesion strength and microhardness of the coatings were evaluated. The results indicated that all factors have significant influence on these properties. Chemical composition of the alloys was the most important factor, followed by the carrier gas pressure, standoff distance and powder feed rate. The addition of Ni, produces coatings with lower levels of oxide content and porosity. An experiment with improved parameters was conducted, and a great improvement on the coating properties was observed.

Thermally sprayed coatings are employed for many purposes, as corrosion protection, wear resistance improvement, resistance to high temperatures, and others. The coating performance depends on its morphology, which is composed by splats, pores, oxide inclusions, and entrapped unmelted or resolidified particles. In arc spray process (ASP), the heat source is the arc electric obtained from the contact of two consumable metallic wires with different electric potentials, and the carrier gas is the compressed air. The velocity, dimensions, and thermal characteristics of the droplets sprayed are related to the morphology and properties of the coating. The main goal of this research is to evaluate how the velocity, temperature, and particle size are modified by the chemical composition of different materials (carbon steel, stainless steels, and FeMnCrSiNi alloy). The intention is to predict how the modification of the process parameters will change the particles properties. The materials had similar behavior tendencies during the flight: the velocity increased to a peak value then decreased, but this maximum value was different for materials with different particle size. The particles’ size did not present significant differences during the flight; and the particles cooled down as they moved away from the gun, except the austenitic stainless steel and the FeMnCrSiNi alloy, which increased the droplets temperature during the travel. These alloys also presented more variation in chemical composition during flight.

The use of the cold gas spray (CGS) process as a metal additive manufacturing (MAM) technique for metallic part production has been deeply studied recently, mainly due to its advantages over other MAM techniques. CGS MAM is a high-productivity technique with a very low level of particle oxidation, microstructural changes, phase transformations, or deleterious residual thermal stresses in the part. The use of CGS MAM to produce maraging parts represents a gain for the industry by saving machining time and preventing raw material waste. Its wear resistance and corrosion behavior were evaluated in this work and were compared with cermet coatings deposited by high-velocity oxy-fuel (HVOF) on the CGS MAM maraging. This work presents the innovative and effective combination of different thermal spraying processes and materials to obtain MAM maraging parts with higher wear resistance, evaluating abrasion, sliding, and water erosion wear types.

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