Assessment of the processability of applying a metal matrix coating by electrochemical deposition on an internal combustion engine cylinder

Introduction. Weight optimization of internal combustion engines is achieved through the use of aluminum alloys. In order to increase the wear resistance of surfaces, functional coatings are used – including those with the inclusion of nanoparticles. Nanoparticles are incorporated into the coating to substantially improve performance properties such as hardness and wear resistance, also to form a more uniform structure. To maintain the gap in the piston-cylinder group, it is important to assess the current state of the surface of the parts and the method of preparing them for applying a metal-matrix wear-resistant coating. Methods and materials. During the study, an integral analysis of the microgeometry of the piston and cylinder surfaces was carried out using a laser scanner (measurement accuracy – 10 microns). Surface of cylinder is coated with Ni–SiC by electrochemical deposition. Samples from different sectors of the inner surface of the cylinder were cut to evaluate the coating. The microhardness was determined using a TBM Tochline microhardness meter at a load of 50 g. The microstructure and chemical composition of the coating were examined using a JSM-6490 LV scanning electron microscope at a magnification of x500. Results and discussion. Analysis of the cylinder and piston microgeometry revealed a nominal radial gap of 250 μm. Deviations of the cylinder dimensions correspond to the 5th degree of accuracy of castings, for the piston – to the 3rd. Bore diameter in cylinder цилиндре 39+0,000 +0,146, piston diameter 38,5–0,150 –0,038. Thickness of coating layer including series-formed main nickel layer with strengthening phase SiC ≈ 900 nm is 160±10 mcm. Average microhardness of the applied coating 420 HV. The cylinder depth variation does not exceed 10 HV, which characterizes the uniformity of the formed nickel-strengthening phases SiC. Conclusion. Before coating, machining of the inner surface of the cylinder is required to equalize the radial gap to 400+10 μm, ensuring a 39+0,39 +0,40 mm. The developed coater ensures geometric and structural uniformity of the coating with a thickness of 160±10 microns. The coated surface shall be finished. In the future, bench tests of the wear resistance of the coating will be carried out. Subsequent studies will be aimed at optimizing the technology of its application in order to achieve an indicator of operating time of 500 hours before overhaul.