Tribological and Mechanical Performance of Ti₂AlC and Ti₃AlC₂ Thin Films

Abstract

Mn+1AXn (MAX) phases are novel structural and functional materials with a layered crystal structure. Their unique properties such as good machinability, high electrical conductivity, low friction, and corrosion resistance are appealing for many engineering applications. Herein, Ti2AlC and Ti3AlC2 MAX thin films are synthesized by magnetron sputtering and subsequent thermal annealing. A multilayer approach is used to deposit single‐element nanolayers of titanium, aluminum, and carbon onto silicon substrates with a double‐layer‐diffusion barrier of SiO2 and SixNy. Ti2AlC and Ti3AlC2 thin films (thickness ≈500 nm) are formed via rapid thermal annealing and verified by X‐Ray diffraction. Nanoindentation tests show hardness values of about 11.6 and 5.3 GPa for Ti2AlC and Ti3AlC2, respectively. The tribological behavior of the Ti2AlC and Ti3AlC2 thin films against AISI 52100 steel balls under dry sliding conditions is studied using ball‐on‐flat tribometry. The resulting coefficient of friction (CoF) for Ti2AlC and Ti3AlC2 ranges between 0.21–0.42 and 0.64–0.91, respectively. The better tribological behavior observed for Ti2AlC thin films is ascribed to its smaller grain size, reduced surface roughness, and higher hardness.

The effect of different annealing temperatures on the mechanical and tribological properties of the Ti2AlN MAX phase films

“…24 Compared to the R1-750 film, Ti 2 AlC and Ti 3 AlC 2 MAX phase films also exhibited lower hardness values of 11.6 and 5.3 GPa, respectively. 40 This is because nitride-based films are inherently harder than carbon-based films, owing to their strong metal-nitrogen bonds. These bonds facilitate the formation of films with a more compact and dense structure and increase their hardness.…”

MAB‐Phases and Beyond—A Tribological Success Story?

“…Mean values of bulk modulus (related to isostatic compression), shear modulus, and Young's modulus show that the selected MAB-phases show fairly similar values to the state-of-the-art MAX-phase (Ti 3 SiC 2 and Ti 3 AlC 2 ), which have already shown promising tribological properties when used as solid lubricant coatings. [38][39][40][41] Notably, attainable chemistries in synthesized MAB-phases have been limited to A = Al and M = Cr, W, Mo, Fe, and Mn, apart from the recently discovered Ti 2 InB 2 . However, the special attention in tribology has been paid to MAB-phases based on Mo, Fe, and Mn (MoAlB, Fe 2 AlB 2 , and Mn 2 AlB 2 ) due to their possible synthesis together with their good mechanical properties.…”

Self‐lubricating effect of solid solution elements on tribological performance of Ti3AlC2 over a wide temperature range

“…More worthy of attention is that Cr 2 AlC and Ti 2 SnC are lately demonstrated with self‐crack healing ability in low oxygen partial pressures and decreased temperatures 21–26 . Additionally, attractive tribological characteristics have been considerably developed, which are primarily associated with the self‐lubricating oxidation‐introduced friction film on the worn surface, along with the dramatic high‐temperature performance and mechanical properties making MAX phases potentially advantageous as solid lubricants in aerospace, high‐speed trains, or marine environment applications with extreme service conditions 4,27–31 …”

“…[21][22][23][24][25][26] Additionally, attractive tribological characteristics have been considerably developed, which are primarily associated with the self-lubricating oxidation-introduced friction film on the worn surface, along with the dramatic high-temperature performance and mechanical properties making MAX phases poten-tially advantageous as solid lubricants in aerospace, highspeed trains, or marine environment applications with extreme service conditions. 4,[27][28][29][30][31] Present research indicated that partial substitution treatment on the M, A, and X sites can be used to modify the mechanical properties of resulted materials due to the solid solution hardening and strengthening effects, as well as to tailor the tribological performance by providing controllable phase composition and oxide proportion of the predominate friction film. [32][33][34][35][36][37][38][39][40][41] Huang et al 35 developed Ti 3 Al(Sn)C 2 solid solution and found that the friction coefficients varied continuously in the range of 0.1-0.4 depending on the varying Sn content, meanwhile maintaining excellent wear resistance under dry sliding against low-carbon steel.…”