Abstract
This study analyzed the mechanical properties of cold-sprayed Cr3C2-25(Ni20Cr) blended with Ni-graphite as a solid lubricant deposited on 7075 aluminum alloy substrate. To optimize the coating properties, different sets of parameters (graphite content in feedstock, process gas composition, spraying distance, and traverse gun speed) were tested in the frame of the Taguchi experiment. The cold-sprayed coatings were evaluated for their chromium carbide and graphite content, hardness, and coefficient of friction. Analysis of the microstructure of the deposited coatings revealed that graphite as a soft and brittle component fills all voids in the coating and its quantity depends on its content in the feedstock. The experimental results show that the composition of the process gas has the greatest impact on the Cr3C2 content in the coating and the proportion of graphite in the sprayed blend directly affects its hardness. In the case of the coefficient of friction, the most significant parameters were the graphite content in the sprayed blend, the spraying distance, and process gas composition. The conducted verification experiment with the optimum parameter values allowed a coating with the highest hardness and the lowest coefficient of friction to be obtained.
Highlights
The emergence of new surface engineering technologies has always been associated with research on obtaining surface layers with better properties than those obtained with the methods used so far
The research currently being conducted covers the deposition of composite coatings with a very diverse share of ingredients and include the matrix containing a solid lubricant [7,8,9]
The analysis of the results revealed that the coldsprayed coating in Experiment 3 exhibited the highest S/N ratio of 29.314 and the coldsprayed coating in this experiment showed the highest chromium carbide content of
Summary
The emergence of new surface engineering technologies has always been associated with research on obtaining surface layers with better properties than those obtained with the methods used so far. Thermal spraying techniques provide wide deposition possibilities of such coatings on the cooperating surfaces of components. They allow the use of materials with significantly different physical and chemical properties, which makes it possible to obtain coatings with the required properties [1,2,3]. The characteristic feature of the cold-spray process is the temperature of the gas stream, which is always below the melting point of the sprayed material. In this process, powder particles are injected into a high-velocity stream of the gas (300–1200 m/s) and accelerated by flowing through a converging—diverging nozzle toward the substrate. The basic problem is the selection of the matrix material and the solid lubricant and determining their mutual proportions
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