Investigation of possibility of fabrication of long-length samples of Ti3AlC2–Al MAX-cermet by the SHS method with spontaneous infiltration by aluminum melt

The article discusses the features of combining the self-propagating high-temperature synthesis (SHS) of the Ti3AlC2 MAX phase porous skeleton with infiltration by aluminum melt in a spontaneous mode in order to obtain enlarged samples of Ti3AlC2–Al ceramic-metal composite (MAX cermet) in an air atmosphere. A new scheme was developed for obtaining long-length SHS cermet samples from a bulk density charge with spontaneous infiltration by melt in the same direction with the combustion wave movement, which makes it possible to regulate the time gap between the end of the Ti3AlC2 synthesis and the beginning of the spontaneous pore filling with aluminum melt. This technology was used to obtain a Ti3AlC2 SHS skeleton with a total length of 250 mm and a diameter of 22–24 mm where the depth of infiltration with pure aluminum was about 110 mm, and impregnation with the Al–12%Si alloy was 130 mm. The paper provides comparative data on density, microstructure, and phase composition at different areas along the length of MAX cermet samples obtained. It was found that infiltration with pure aluminum destroys the Ti3AlC2 MAX phase to transform it into a mixture of TiC + TiAl3 phases in the SHS cermet, and 12 % Si added to the Al melt promote Ti3AlC2 preservation in the cermet to a some extent. Instead of MAX cermet samples with the target composition of Ti3AlC2–Al and Ti3AlC2–(Al–12%Si), long-length samples of SHS cermets with a different actual phase composition were obtained: TiC–TiAl3–Al and TiC–Ti3AlC2–TiAl3–(Al–12%Si), respectively, where the Ti3AlC2 MAX phase either practically absent or present in small quantities. The average hardness values of TiC–TiAl3–Al and TiC–Ti3AlC2–TiAl3–(Al–12%Si) SHS cermets were HB = 640 and 740 MPa, density ρ = 2.88÷3.16 g/cm3 and 3.03÷3.13 g/cm3, and residual porosity П = 17.0÷24.6 % and 17.6÷20.3 %, respectively.