| High Temperature Stability in Oxygen and Hydrogen Environments and Wear Resistance of Ti,Nb-Al-C MAX Phases Tetiana Prikhna1; Tetiana Serbenyuk2; Vladimir Sverdun2; Fernand Marquis3; Orest Ostash4; Viktoriya Podhurska5; Alexander Kuprin6; Myroslav Karpets1; Semyon Ponomarov7; 1INSTITUTE FOR SUPERHARD MATERIALS, Kiev, Ukraine; 2INSTITUTE FOR SUPERHARD MATERIALS OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE, Kiev, Ukraine; 3SAN DIEGO STATE UNIVERSITY, San Diego, United States; 4KARPENKO PHYSICAL-MECHANICAL INSTITUTE OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE, Lviv, Ukraine; 5PHYSICO-MECHANICAL INSTITUTE OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE, Lviv, Ukraine; 6NATIONAL SCIENCE CENTER KHARKOV INSTITUTE OF PHYSICS AND TECHNOLOGY, Kharkov, Ukraine; 7INSTITUTE OF SEMICONDUCTOR PHYSICS, Kiev, Ukraine; PAPER: 107/AdvancedMaterials/Keynote (Oral) SCHEDULED: 15:55/Fri. 25 Oct. 2019/Leda (99/Mezz. F) ABSTRACT: MAX phases of Ti-Al-C system are the most examined and perspective for high temperature applications; they are light, electro conductive, having high damping and low friction abilities, etc. But despite the combination of unique properties they did not find yet wide spread application (it is difficult to synthesize single phased material, they should combine a set of properties and even the singlephased materials can have very different characteristics because of synthesis parameters) [1]. The bulk Ti<sub>2</sub>AlC, Ti<sub>3</sub>AlC<sub>2</sub> and (Ti,Nb)<sub>3</sub>AlC<sub>2</sub> developed by us are promising for the manufacture of interconnects of solid hydrogen fuel cells, pantograph, as damping substrates under the incisors, and others. The films with an approximate stoichiometry of Ti<sup>3.3-3.9</sup>AlC<sub>1.4-1.6</sub> (5 I�m thick) deposited on Ti substrate using a vacuum-arc method from the hota�� pressed target (Ti<sub>2</sub>AlC (57 wt.%) +Ti<sub>3</sub>AlC<sub>2</sub> (43 wt.%)) were extremely promising for high-temperature applications, in particular for interconnects fuel cells and as cavitation resistant coatings on turbines. After 1000 h heating at 600 <sup>o</sup>C the surface electrical conductivity of the films only slightly decreased from 0.01 to 0,01-3 Ohm while the surface of pure Ti after 250 h in the same conditions totally oxidized and lost conductivity. Investigation of the influence of H<sub>2</sub> for 3 - 40 h and oxidation up to 1000 h at 600 <sup>o</sup>C, as well as thermocycling in air up to 600 <sup>o</sup>C on the bending strength and mass change of Ti<sub>3</sub>AlC<sub>2</sub>, (Ti,Nb)<sub>3</sub>AlC<sub>2</sub>, Ti<sub>2</sub>AlC showed that the highest absolute value demonstrated Ti<sub>2</sub>AlC and it was the most stable in the oxide medium (seems due to presence of some oxygen in the structure - Ti<sub>2.2</sub>AlC<sub>0.9</sub>O<sub>0.17</sub>). The bending strength of the Ti<sub>3</sub>AlC<sub>2</sub> and (Ti,Nb)<sub>3</sub>AlC<sub>2</sub> even increased after heating in H<sub>2</sub>. The addition of Nb allowed increasing the stability of the MAX phase in H<sub>2</sub>, and in air (the oxide film was twice thinner than that on the samples without Nb after 1000 h heating at 600 <sup>o</sup>C). The high temperature X-rays showed that Ti<sub>2</sub>AlC was oxidized more intensive than Ti<sub>3</sub>AlC<sub>2</sub> at higher temperatures (Ti<sub>2</sub>AlC was stable up to 700- 750 <sup>o</sup>C and Ti<sub>3</sub>AlC<sub>2</sub> - up to 1050-1100 <sup>o</sup>C). The most stable at thermal cycling to 1200 <sup>o</sup>C was a high-density material based on the MAX phase Ti<sub>3</sub>AlC<sub>2</sub>, obtained by two-stage technology (synthesis in vacuum with subsequent compression by hot pressing at 30 MPa). The oxidized layer of specimens contained ~100% of Ti<sub>3</sub>AlC<sub>2 </sub>but synthesized by one-stage hot pressing at 15-30 MPa for 10-30 min was twice thicker. The wear of Ti<sub>3</sub>AlC<sub>2</sub> materials obtained at 30 MPa according to the one- and two-stage technologies was very low (as compare to silumin), but the wear of the copper in contact with them was rather high. Significant reduction of wear of copper was achieved when the manufacturing pressure was reduced to 15 MPa: during friction in pair with copper its wear resistance in comparison with traditionally used silumin was 40 times higher, and the wear of copper was 14 times smaller (after 6 km of the way); Besides, Ti<sub>3</sub>AlC<sub>2 </sub>demonstrated much higher arc resistance. References: [1] T. Prikhna, O. Ostash, V. Sverdun, M. Karpets, T. Zimych, A. Ivasyshin, T. Cabioca��h, P. Chartier, S. Dub, L. Javorska, V. Podgurska, P. Figel, J. Cyboroń, V. Moshchil, V. Kovylaev, S. Ponomaryov, V. Romaka, T. Serbenyuk, A. Starostina Presence of oxygen in Ti-Al-C MAX phases-based materials and their stability in oxidizing environment at elevated temperatures // Acta Physica Polonica A. - 2018. - Vol. 133, a�� 4. - P. 789-793 |
