Ni-SiC composite coating obtained by electrodeposition

Introduction. One of the common types of coatings is a composite coating based on nickel reinforced with solid particles of silicon carbide SiC. It has high anti-wear properties and is widely used to increase the strength of the working surfaces of internal combustion engine cylinders. The basic technology for applying the coating is electrodeposition. The quality of the coating is affected by the size of the solid particles. Difficulties in forming a composite arise when moving to a large fraction of 20–25 μm, especially when moving from flat samples to long axisymmetric parts. The aim of the research is to study the technological potential of creating a Ni-SiC coating on flat samples simulating a sector of an axisymmetric part. Methods and materials. The research part of the work was carried out on samples of aluminum alloy AK7. Electrodeposition mode: current density 10 A/dm2; duration 60 minutes; temperature 60 °С. The microstructure of the coatings was studied using an Olympus GX51 optical microscope. Coating wear resistance tests were performed using a CSM Micro-Scratch Tester. Microhardness was assessed using a DuraScan 50 microhardness tester. Roughness Ra was determined using a Mitutoyo Surftest profilometer. Results and discussion. The article considers the features of the process of forming a composite coating based on Ni-SiC by the electrodeposition method. A model of the action of electrostatic, gravitational and centrifugal forces on SiC particles in the electrolyte solution for electrodeposition is presented. Based on the model, an installation was designed, on which the technological process of applying a composite Ni-SiC coating to flat samples of aluminum alloy AK7, simulating a sector of an axisymmetric part, was successfully tested. Due to the possibility of rotating the installation during the electrodeposition, three types of coating were obtained: nickel-based «Ni»; nickel-based with silicon carbide particles ”Ni-SiC”; layered coating. Conclusion. The nickel coating with a uniform distribution of SiC particles is characterized by the maximum microhardness value, increased roughness and a small groove width after the scratch test, which indicates good adhesion to the substrate material.