High temperature tribological behaviour of Ti2AlC and Ti3AlC2 MAX-phases synthetized by SPS from Ti/Al/TiC powder mixtures
DUPONT V. 1, BOILET L. 1, ERAUW J. 1
1 BCRC (Belgian Ceramic Research centre), MONS, Belgium
Ternary compound MAX phase ceramics have attracted more and more attention in recent years thanks to the considerable advantages resulting to a large extent from their unique nano-lamellar crystal structure: high strength, resistance to elevated temperature decomposition and chemical corrosion, etc. These compounds possess as well high damage tolerance a.o at elevated temperature due to their intrinsic ductile-to-brittle transition, oxidation and thermal shock resistance, high thermal conductivity and low expansion coefficient. These properties combined with their lamellar structure make accordingly those materials promising candidates for demanding tribological applications.
In the present study, high purity Ti2AlC and Ti3AlC2 bulk ceramic were synthetized by Spark Plasma Sintering from Ti/Al/TiC powder mixtures, respectively, at 1400°C during 10 minutes and 1350°C during 15 minutes, under 35 MPa. Their resulting purity, as assessed by XRD characterization, was above 98%. Their tribological behavior was investigated at room temperature as well as at elevated temperature up to 600°C on a Tribolab (BRUKER) tribometer. The sliding friction and wear tests were performed using 10 mm diameter WC ball as counterpart. The tests were carried out at each temperature investigated, under a load of 5 and 10 N, using a linear drive with a track of 5 mm, at 10 Hz frequency corresponding to a sliding speed of 0.1 m/s. The total duration of the test was 5000 s, corresponding to a total 500 m distance.
Worn surfaces were investigated, on each MAX-phases, by scanning electron microscopy, level of oxidation was measured using EDX spectrometry, and wear volume was evaluated by 3D profilometer.
At room temperature, the tribological behavior of MAX phases were characterized by a high wear rate (> 10-4 mm³/N.m). However, at high temperature, the wear rate decreases below 10-6 mm³/N.m. The formation of a lubricious tribofilm at the contact areas could be responsible for these low values.