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To improve the wear resistance of the low-pressure turbine cowling ring's Ti6Al4V (TC4) alloy surface and suppressing the generation of cracks during laser cladding, TiC/Ti3Al-reinforced Ti-based composite coatings on TC4 alloy surface were fabricated through laser cladding by TC4-coated TiC mixed powder with different Ti2AlC contents (0, 10 wt.%). Results show that the composite coatings have no cracks due to TiC coated by TC4, the hard phase TiC is uniformly distributed in all regions of the coatings, and the physical phases of the two coatings mainly consist of α-Ti matrix phase, hard phases TiC, Ti3Al, and Fe-Ti-V solid solution. Besides, coatings with weight fractions of 0 and 10% Ti2AlC have an average hardness of 482 ± 3.81 and 535.3 ± 3.41 HV0.5, respectively, which is approximately 1.51 and 1.67 times that of the substrate hardness (320 ± 1.81 HV0.5). Besides, for the coating added with Ti2AlC, the lowest coefficient of friction (COF) (30 N, 0.267 at 500 °C) and the strongest wear resistance (30 N, 0.92 × 10−6 mm3/N m at 500 °C) were obtained relying on the synergistic effect of Al2O3, TiO2 oxide film and the hard phases TiC and Ti3Al. Because of tearing of the Al2O3 and TiO2 oxide films on composite coating surface under high loading at (60 N, 500 °C), the friction coefficient and the wear rate started to increase. Ti2AlC-coated composites mainly undergo hard phase peeling, three-body abrasive wear, slight oxidation wear and adhesive wear at room temperature, and the primary wear mechanisms are slight adhesive wear, abrasive wear and oxidation wear at (30 N, 500 °C) and severe adhesive wear, abrasive wear and oxidation wear at (60 N, 500 °C). [ABSTRACT FROM AUTHOR]

By applying the TC4-Ti2AlC composite coatings to the Ti6Al4V substrate by laser, the wear resistance of the Ti6Al4V alloy was improved. Analysis was done on the composite coatings' microstructure, phase composition, microhardness, and tribological characteristics. According to the findings, coatings without defects can be created when Ti2AlC content ranges between 5 and 15 wt.%. Furthermore, the coating without Ti2AlC consisted of a α-Ti solid solution while coatings with Ti2AlC included a α-Ti solid solution, hard phases of TiC and Ti3Al, as well as a Ti2AlC ceramic phase. During laser cladding, Ti2AlC partially dissolved and turned into TiC and Ti3Al, resulting in an average hardness of 371.61 ± 3.95 HV0.5, 382.92 ± 3.61 HV0.5, 388.91 ± 3.29 HV0.5 for the coatings with Ti2AlC weight fractions of 5, 10, and 15%, respectively. These numbers were about 1.16 ~ 1.22 times the hardness of the titanium alloy matrix (320 ± 3.12 HV0.5). Besides, the Ti2AlC lubricant and hard phases act synergistically to bring composite coatings better performances in wear resistance and friction reduction compared to the pure TC4 coating. The lowest coefficient of friction (0.382) (COF) and the greatest wear resistance (8.87 × 10−5 mm3/N m) were obtained at the composition of TC4-10wt.%Ti2AlC; more particularly, the wear resistance at TC4-10wt.%Ti2AlC was 1.2–2.1 times that of pure TC4 coating. The principal causes of wear in a pure TC4 coating are adhesive wear and oxidation, however, these wear processes shift to minor abrasive wear and oxidation when assisted by oxide coatings, Ti2AlC lubricant, and TiC, Ti3Al hard phases. [ABSTRACT FROM AUTHOR]

• Laser cladding of TC4 coating on cast iron, no cracking, max hardness 480.9 HV. • Scan speed 13 mm/s, 500 W 1st layer, 600 W 2nd layer, eradicated ledeburite. • 600 W coating outperforms 800 W & 1000 W in wear resistance at RT & 500 ℃. To enhance the wear resistance of the HT250 surface and eliminate ledeburite formation at the coating-substrate interface, a dual-layer Ti-6Al-4 V coating was created on HT250 surfaces through laser cladding. The influence of varying laser power on the microstructure, hardness, and wear resistance was investigated. The results indicate that a laser power of 600 W for the second layer can eliminate the formation of ledeburite at the coating-substrate interface, fabricating a crack-free cladding layer with a maximum hardness of 480.9 HV. Needle-like TiC was in-situ synthesized in the surface zone when the laser power was set at 600 W and 800 W. The surface hardness at 600 W is 1.1 and 1.4 times higher than that at 800 W and 1000 W, respectively. The optimal wear resistance was achieved at a laser power of 600 W, exhibiting 0.52 and 0.40 times the wear rates compared to those at 800 W and 1000 W, respectively, at 500 °C. At temperatures below 300 °C, the predominant wear mechanisms for all three coatings were abrasive wear and a small amount of oxidative wear. As the temperature increased to 500 °C, oxidative wear became the primary wear mechanism for the coatings. [ABSTRACT FROM AUTHOR]