Microstructure and properties of MAX-based composites manufactured from Ti3SiC2-based and Ti/SiC powders by FAST/SPS in vacuum

Abstract

The synthesis of MAX-based composites from Ti3SiC2-based and non-stoichiometric Ti/SiC powders was developed via field-assisted sintering technology/spark plasma sintering (FAST/SPS) in vacuum at temperatures ranging from 1350 to 1450 °C, with a heating rate of 200 °C/min, holding time from 1.5 to 15 min, and a compaction pressure of 60 MPa. The phase composition of the powders and composites was analyzed using X-ray diffraction (XRD), while the microstructure was examined by means of light microscopy (LM) and scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDS). The specific features of the MAX phase microstructure formation from the mechanically alloyed powder were defined. The hardness, nanohardness, Young's modulus, and strain gradient model parameters were determined. Calculations based on load-displacement curves allowed to indicate such materials' properties as Young's modulus, true hardness, and characteristic depth. The friction and wear behavior were investigated at temperatures ranging from 20 to 700 °C and test loads from 10 to 40 N, revealing self-lubricating effects during sliding. A near-zero wear effect at high temperatures was found for the composites sintered from non-stoichiometric Ti/SiC powder. The resulting composites exhibited hardness of 810–860 HV10 and fracture toughness of 5.5–6.5 MPa m1/2 for the samples sintered from Ti3SiC2-based powder and hardness of 1100–1200 HV10 and fracture toughness of 5.0–5.3 MPa m1/2 for the samples sintered from Ti/SiC powder. In both cases, Ti3SiC2 was the dominant phase, while TiSi2, SiC, and TiC were also present in the microstructure of the sintered samples.