  Herein we report on the reactivity between palladium, Pd, and the MAX phases,
Ti${_2}$AlC, Ti${_3}$AlC${_2}$, Ti${_3}$SiC${_2}$ and Cr${_2}$AlC. Diffusion
couples of Pd/MAX were heated to 900 {\deg}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 {\deg}C for 10 h,
the diffusion layer thicknesses in the Ti${_2}$AlC/Pd, Cr${_2}$AlC/Pd,
Ti${_3}$AlC${_2}$/Pd and Ti${_3}$SiC${_2}$/Pd couples were found to be 35, 45,
105 and 410 mm, respectively. Thus, Ti${_2}$AlC is the most resistant to
reaction, while Ti${_3}$SiC${_2}$ is least resistant, with Cr${_2}$AlC and
Ti${_3}$AlC${_2}$, 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.
