ORALS

SESSION: AdvancedMaterialsFriPM2-R2	5th Intl. Symp. on New and Advanced Materials and Technologies for Energy, Environment and Sustainable Development
Fri Oct, 25 2019 / Room: Leda (99/Mezz. F)
Session Chairs: Tetiana Prikhna; Ruiyuan Liu; Session Monitor: TBA

15:55: [AdvancedMaterialsFriPM209] Keynote
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 Id: 107 [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 Ti₂AlC, Ti₃AlC₂ and (Ti,Nb)₃AlC₂ 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^3.3-3.9AlC_1.4-1.6 (5 I�m thick) deposited on Ti substrate using a vacuum-arc method from the hota�� pressed target (Ti₂AlC (57 wt.%) +Ti₃AlC₂ (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 ^oC 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 H₂ for 3 - 40 h and oxidation up to 1000 h at 600 ^oC, as well as thermocycling in air up to 600 ^oC on the bending strength and mass change of Ti₃AlC₂, (Ti,Nb)₃AlC₂, Ti₂AlC showed that the highest absolute value demonstrated Ti₂AlC and it was the most stable in the oxide medium (seems due to presence of some oxygen in the structure - Ti_2.2AlC_0.9O_0.17). The bending strength of the Ti₃AlC₂ and (Ti,Nb)₃AlC₂ even increased after heating in H₂. The addition of Nb allowed increasing the stability of the MAX phase in H₂, and in air (the oxide film was twice thinner than that on the samples without Nb after 1000 h heating at 600 ^oC). The high temperature X-rays showed that Ti₂AlC was oxidized more intensive than Ti₃AlC₂ at higher temperatures (Ti₂AlC was stable up to 700- 750 ^oC and Ti₃AlC₂ - up to 1050-1100 ^oC). The most stable at thermal cycling to 1200 ^oC was a high-density material based on the MAX phase Ti₃AlC₂, 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 Ti₃AlC₂but synthesized by one-stage hot pressing at 15-30 MPa for 10-30 min was twice thicker. The wear of Ti₃AlC₂ 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, Ti₃AlC₂demonstrated 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