Friction and wear behavior of fluoride added Si₃N₄-SiC ceramic composites at elevated temperature

The addition of fluoride phases often provides promising wear resistance characteristics in ceramic matrix composites at elevated temperatures. In this work, MgF2 added Si3N4–SiC nanowire composite is successfully fabricated to enhance wear resistance capabilities at 500OC. Tribological characteristics of Si3N4–SiC composite with the addition of fluoride phase are reported here. The composite matrix with 5 wt.% MgF2 shows a significant decrease in coefficient of friction by ∼25.40% and an improvement of specific wear rate by ∼78.35%, by providing a tribo layer at the mating interfaces. Moreover, the composite can achieve a high fracture toughness of ∼10.56 MPa.m0.5 with the addition of SiC nanowires. However, the addition of a higher amount of (>5 wt.%) fluoride diminishes the mechanical properties of the ceramic composite. This leads to a change of wear mechanism from delamination to abrasion, causing a higher wear rate.