Analytical description and tribological performance of Si 3 N 4 -MoSi 2 nanocomposites

Abstract

Silicon nitride (Si₃N₄) reinforced with molybdenum disilicide (MoSi₂) offers improved oxidation resistance and tribological stability compared to monolithic ceramics. This study presents comprehensive analytical modeling and validation of nano-sized Si₃N₄-MoSi₂ composite friction and wear behavior under reciprocating dry sliding against SiC counterface. Tribological testing was conducted at normal loads of 6–46 N and sliding frequencies 0.25–1.0 Hz, providing experimental database comprising friction coefficient evolution curves and specific wear rates. Novel analytical expressions incorporating sigmoidal and polynomial functions were developed and systematically validated to describe: friction coefficient evolution with cycle number at each load and frequency; steady-state friction dependence on normal load and frequency; and specific wear rate variation. Model fitting achieved R² > 0.95 for both transient and steady-state regimes, with normalized root-mean-square errors below 5%. The validated analytical framework captures quasi-linear load dependence and substantial frequency sensitivity (32% friction reduction from 0.25 to 1.0 Hz), while wear rate exhibits non-monotonic load dependence with minimum at approximately 30 N. Mechanistic analysis reveals that MoSi₂ functions as structurally compliant refractory phase facilitating mixed-oxide tribolayer formation. Compact design equations derived herein are directly implementable in component-level tribological simulations and bearing life prediction models.