Effect of surface roughness, elastic modulus, and hardness on wear and friction in borided AISI M2 steel substrates

Abstract Thermochemical boriding treatment is a surface hardening process that increases the wear resistance and service life of mechanical components and tools made of steel. The tribological analysis of the FeB/Fe2B biphasic boride layer is of great importance to reduce the energy consumption in frictional contacts and the manufacturing costs associated with wear of machinery elements. In this experimental study, the powder pack technique was used to perform the thermochemical boriding treatment on AISI M2 steel substrates using different combinations of temperature and exposure time, to obtain a FeB/Fe 2 B biphasic boride layer. The boride layer was characterized by x-ray diffraction, scanning electron microscopy (SEM), nanoindentation, and contact profilometry. The wear and friction of the surface of unborided AISI M2 steel and FeB/Fe 2 B biphasic boride layer in contact with an alumina (Al 2 O 3 ) ball were evaluated using the pin-on-disc test under dry conditions. Several statistical techniques were used to determine that there is a linear relationship between surface hardness and wear depth of the FeB/Fe 2 B biphasic boride layer: descriptive statistics, Shapiro-Wilk normality test, Pearson and Spearman correlation coefficients, linear regression analysis, R-squared, adjusted R-squared and Durbin Watson test. In addition, the results show that the boriding increases the wear resistance of AISI M2, although on substrates borided at 1173 K for 6 h, 1223 K for 4 h and 1223 K for 8 h, this resistance was lower. The coefficient of friction of the unborided substrate was higher (0.81) than that of the borided substrates (0.70–0.77). In contrast, the duration of the transient state of the unborided substrate is shorter than that shown by the borided substrates.