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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]

In this paper, an integrated fault diagnosis and fault tolerant control algorithm was proposed for a non-Gaussian nonhnear stochastic distrihution control system. The RBF neural networks observer based fault diagnosis and PI tracking fault tolerant control were integrated to he designed. The rational square-root B-spline model was used to represent the output probability density function (PDF), On the basis of designed nonlinear neural network observer, a new fault diagnosis algorithm was developed to diagnose the slow-varying fault in the dynamic part of such systems, Convergency analysis was performed for the error dynamics raised from the fault detection and diagnosis phase. With the information of fault diagnosis, a new fault tolerant control scheme based on PI tracking strategy was designed so that the post-fault probability density function could still track the given distribution, A simulated example has been given to illustrate the efficiency of the proposed algorithms. [ABSTRACT FROM AUTHOR]