Quaternary diborides—improving the oxidation resistance of TiB_2 ± z coatings by disilicide alloying

Figures & data

Table 1. Chemical composition, crystallographic parameters (c/a ratio), and mechanical properties (H and E) for all grown Ti-(TM)-Si-B_2 ± z coating materials.

	Chemical composition [at. %]
Coating material	Ti	Ta	Mo	Si	B	O	B/(Ti + TM)	c/a	H [GPa]	E [GPa]
TiB2.57	27.7	–	–	–	71.2	1.1	2.57	1.054	38.2 ± 3.3	552.0 ± 90.2
Ti0.25Si0.08B0.67	23.9	–	–	7.6	65.5	2.6	2.74	1.051	30.4 ± 1.6	443.9 ± 21.5
Ti0.26Si0.15B0.59	25.7	–	–	14.2	58.2	1.6	2.26	1.054	23.7 ± 1.0	399.0 ± 21.5
Ti0.31Ta0.04Si0.06B0.59	30.4	3.7	–	6.1	58.4	1.3	1.72	1.032	32.8 ± 2.8	439.7 ± 29.5
Ti0.28Ta0.07Si0.12B0.53	27.7	6.8	–	11.6	52.5	1.3	1.52	1.041	36.0 ± 2.5	434.8 ± 26.1
Ti0.24Mo0.05Si0.12B0.59	23.3	–	5.2	11.6	57.4	2.2	2.01	1.042	27.3 ± 1.0	428.1 ± 10.0
Ti0.23Mo0.07Si0.16B0.54	22.7	–	6.6	16.2	52.2	2.1	1.78	1.034	24.4 ± 0.9	409.1 ± 25.7
Ti0.20Mo0.11Si0.26B0.43	19.8	–	10.3	25.5	42.1	1.8	1.40	–	19.1 ± 1.0	330.9 ± 17.4

Figure 1. X-ray diffractograms of (a) TiB_2.57, (b) Ti-Si-B_2 ± z, (c) Ti-Ta-Si-B_2 ± z, and (d) Ti-Mo-Si-B_2 ± z alloyed coatings with their stoichiometries indicated.

Figure 2. Thermogravimetric (TG) curves of mass change during dynamic oxidation of (a) Ti-Si-B_2 ± z, (b) Ti-Ta-Si-B_2 ± z, and (c) Ti-Mo-Si-B_2 ± z coatings in synthetic air under heating rate of 10°C/min. The TG curve for the binary coating TiB_2.57 is indicated by a dashed line in (a), (b) and (c).

Figure 3. TEM analysis of Ti_0.28Ta_0.07Si_0.12B_0.53 coating oxidized in ambient air at 800°C for 1 h. (a) BF image of the whole coating with the substrate at the bottom and oxide scale on top. (b) magnified area of the oxide scale with coating interface. (c) SAED image for the area indicated in (a). (d) STEM image and corresponding EELS maps for the area illustrated in (b).

Figure 4. TEM analysis of Ti_0.23Mo_0.07Si_0.16B_0.54 coating oxidized in ambient air at 1200°C for 1 h. (a) BF image of the whole coating with the substrate at the bottom and oxide scale on top. (b) magnified area for oxide scale with coating interface. (c₁) and (c₂) SAED patterns for areas indicated in (a). (d) elemental EELS maps for the area illustrated in (b).

Figure 5. As-deposited hardness of diverse alloyed TiB_2 ± z coatings in relation to their oxidation temperature T_ox. The obtained scale thickness (at T_ox) for each coating is indicated in relation to the reported oxidation time. The as-deposited coating thicknesses are: 2 µm for Ti_0.26Si_0.15B_0.59, 4.9 µm for Ti_0.28Ta_0.07Si_0.12B_0.53, 3.5 µm for Ti_0.23Mo_0.07Si_0.16B_0.54, 4.9 µm for Ti_0.20Mo_0.11Si_0.16B_0.54, 400 nm for TiB_1.43 [16], 980 nm for Ti_0.9Al_0.1B_1.3 [26], 1.3 µm for (Ti_0.35Al_0.65)B₂ [25], ∼1.5 µm for (Ti_0.68Al_0.32)B_1.35 [18],and ∼1.4 µm for Ti_0.13Si_0.41B_0.46 [27].

Thörnberg J, Bakhit B, Palisaitis J, et al. Improved oxidation properties from a reduced B content in sputter-deposited TiBx thin films. Surf Coat Technol. 2021;420:127353. doi:10.1016/j.surfcoat.2021.127353

 Web of Science ®Google Scholar

Thörnberg J, Mráz S, Palisaitis J, et al. Oxidation resistance and mechanical properties of sputter-deposited Ti0.9Al0.1B2-y thin films. Surf Coat Technol. 2022;442:128187. doi:10.1016/j.surfcoat.2022.128187

 Web of Science ®Google Scholar

Kashani N, Mráz AH, Holzapfel S, et al. Synthesis and oxidation behavior of Ti0.35Al0.65By (y=1.7–2.4) coatings. Surf Coat Technol. 2022;442:128190). doi:10.1016/j.surfcoat.2022.128190

 Web of Science ®Google Scholar

Bakhit B, Palisaitis J, Thörnberg J, et al. Improving the high-temperature oxidation resistance of TiB2 thin films by alloying with Al. Acta Mater. 2020;196:677–689. doi:10.1016/j.actamat.2020.07.025

 Web of Science ®Google Scholar

Glechner T, Oemer HG, Wojcik T, et al. Influence of Si on the oxidation behavior of TM-Si-B2±z coatings (TM = Ti, Cr, Hf, Ta, W). Surf Coat Technol. 2022;434:128178. doi:10.1016/j.surfcoat.2022.128178

 Web of Science ®Google Scholar