On the interactions of Ti₂AlC, Ti₃AlC₂, Ti₃SiC₂ and Cr₂AlC with palladium at 900 °C

Herein we report on the reactivity between palladium, Pd, and the MAX phases, Ti₂AlC, Ti₃AlC₂, Ti₃SiC₂ and Cr₂AlC. Diffusion couples of Pd/MAX were heated to 900 °C under uniaxial stress of ∼20 MPa for 2, 4, and 10 h in a vacuum (<1 Pa) hot press. The diffusion couples were examined using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. After heating to 900 °C for 10 h, the diffusion layer thicknesses in the Ti₂AlC/Pd, Cr₂AlC/Pd, Ti₃AlC₂/Pd and Ti₃SiC₂/Pd couples were found to be 35, 45, 105 and 410 μm, respectively. Thus, Ti₂AlC is the most resistant to reaction, while Ti₃SiC₂ is least resistant, with Cr₂AlC and Ti₃AlC₂, in between. In all cases, the reaction occurred by the diffusion of the A-group element into Pd, concomitant with Pd diffusion into the MAX phase. No diffusion of the M and X atoms was detected.