The association of chemical composition microstructure and tribological properties of the coating on the 25CrMo4 DIN substrate by the SMAW process

In the present study, the effect of chromium carbide element on microstructure, hardness and abrasive properties of welded coating on the DIN-25CrMo4 substrate was investigated. For this purpose, three groups of roughing electrodes with different chromium content (0-13 wt%) were made and roughing operation was performed by hand electrode arc process (SMAW). Optical and scanning microstructural studies (SEM) along with XRD fuzzy analyzes showed that with increasing chromium content the microstructure of the coating is varied from a ferritic field with needle and morphology morphologies into a rich austenite field of carbide phases such as (FeCr) 7C3. The evaluation of the characteristics of roughened samples showed that the coating hardness increased by about 350% with increasing chromium content (the hardness of the chromium-plated coating and the hardness of the metal substrate were 875 ± 5HV and 200 ± 5HV respectively). Examining the wear behavior of the samples indicates a significant improvement in the wear resistance of the chromium-rich coating (an 80% reduction in the coefficient of friction and a 90% reduction in the amount of lost weight relative to the metal-tensile properties) The SEM study of washed surfaces implying a change in the wear mechanism from the two-body scrubbing wear to the cutting mechanism by increasing the volume fraction of carbide compounds in higher-chromium specimens.