Mechanical and Wear Behavior of Cobalt Based Composite with In-Situ Carbide Formed via Decomposition of Ti₃SiC₂

Metal matrix composites (MMCs) are usually designed with excellent wear resistance and mechanical properties when they are used as mechanical moving parts. One way to enhance mechanical strength and improve wear resistance is to add an appropriate amount of hard ceramic phase. But these improvements are always achieved at the cost of plasticity or fracture toughness, which limits the further application of MMCs in some high-load and impact conditions. In this study, Co-based composites with Ti₃SiC₂ additions were prepared by spark plasma sintering (SPS). During sintering, Ti₃SiC₂ was decomposed to form in situ the fine dispersed TiC that developed orientation relationship of (200)_γ-Co//(220)_TiC with the cobalt matrix. Relying on good interfacial bonding between the in-situ formed TiC and the alloy matrix, the composite material exhibits high fracture toughness of 39.1 MPa m^1/2 and low wear rate of 4.7 × 10⁻⁵ mm³N⁻¹ m⁻¹. Owing to its high fracture toughness, fatigue cracks were effectively hindered to nucleate and expand under the subsurface layer. It suffers from just slight abrasive wear. In comparison, the composites with addition of ex situ TiC or Cr₂O₃ exhibit low fracture toughness of 20~26 MPa m^1/2. During friction, they are subjected to serious fatigue and abrasive wear, leading to a high wear rate of 19.7~20.4 × 10⁻⁵ mm³N⁻¹ m⁻¹.