TiN coating plays a positive role in improving the abrasion resistance and impact resistance of aero-engines in sand and dust environments. However, little research has been done on the laser cleaning of TiN coatings that failed on aircraft engines. In this paper, TiN coatings are deposited on Ti6Al4V alloys by magnetic filtered cathodic vacuum arc (MFCVA). The TiN coating was laser cleaned with different parameters. By analyzing coating morphology, surface composition and sample profile, the research reveals the morphological change of the TiN coating after cleaning and the laser cleaning mechanism. The results show that for TiN–Ti6Al4V structure, when the laser average power density is 2.54 × 10³ W/cm², the cleaning mechanism of the coating is thermal expansion; The laser average power density is increased to 5.08 × 10³ W/cm², the cleaning mechanism is thermal expansion, accompanied by the thermal melting of the substrate, a small amount of molten substrate overflows from the crack. When the laser average power density is 5.08 × 10³ W/cm² and the number of cleanings doubles, the cleaning direction is perpendicular to each other, the cleaning mechanism is thermal expansion and thermal melting, both the substrate and the coating are melted, and the cleaning is obviously effective.

Sand erosion has always been a key threat to the performance and service life of aero-engines. The compressor, the key component installed at the front of the aero-engine, suffers the most from sand erosion, especially compressors serving in deserts. Ceramic hard coating is a traditional way to improve the hardness and wear resistance of cutting and grinding tools. It may also be used to improve the erosion resistance of aero- engine compressor. However, the mechanism of erosion damage is complicated, which may include wear, secondary erosion, anisotropic erosion, impact, and fatigue. Recent research discovered the major problems with ceramic hard coating on aero-engine compressors. In this paper, these following problems are discussed: the design of coating material and structure, the preparation method and technology, the effects of droplets and clusters of coating surface, microstructure and characteristics of interface. The review of the major problems and possible solutions discussed in this paper may contribute to the future research on erosion coating theoretically and practically.

Ceramic coating is an effective method for improving the erosion resistance of a material, particularly for titanium alloys. In this study, a TiN/ZrN (ceramic/ceramic) nanoscale multilayer coating is designed and prepared on the Ti6Al4V titanium alloy surface by the physical vapor deposition (PVD) process. The cross-sectional microstructure and phase composition are measured using SEM and XRD, respectively. The hardness, elastic modulus, and adhesion of the coating are measured by the nano-indentation and scratch method. The erosion test is conducted at a 45° angle with 100 m/s velocity using self-developed erosion equipment. The erosion resistance mechanisms of both the substrate and the coating are revealed more intuitively through a single sand particle impact test. The results show that the erosion resistance rate of the coating is 15.5 times higher than that of the titanium alloy substrate. The damage mechanisms of material removal of the coating include crack deflection, crack branching, and succeeding interaction between them when suffering an impacting load. These cracks are started from the droplets and the stress concentrations on the coating surface during the preparation of coating. They are the primary reasons for the decrease in the erosion resistance of the coating. This research is important for the optimization of the erosion-resistant coating structure.

TiN/ZrN multilayers can effectively improve the erosion resistance of metals, particularly titanium alloys employed in aero engines. To explore the corrosion damage mechanism of TiN/ZrN nanoscale multilayers (nanolaminate), a novel [TiN/ZrN]₁₀₀ nanolaminate coating was deposited on Ti-6Al-4V alloys by multi-arc ion plating method. Salt spray corrosion tests and hot corrosion experiment were carried out to evaluate the corrosion resistance of the coating. The corrosion and damage mechanisms were explored with the help of detailed microstructure, phase composition and element distribution characterizations. The salt spray corrosion tests showed that the [TiN/ZrN]₁₀₀ nanolaminate coating possessed good corrosion resistance, which protected substrate against the corrosion. The low temperature hot corrosion tests showed that the oxidation occurred on the surface of the coating, which improved the oxidation resistance of the sample. However, the oxidized droplets squeezed the coating, and destroyed the oxidized layers. As a result, the coating was peeled off from the substrate. The research highlights the corrosion resistance of the novel TiN/ZrN nanolaminate coating and offers a support for their application in engine compressor blade.

Coatings of 3 μm CrN and TiN were prepared by a magnetic filtered cathodic vacuum arc process (MFCVA) on Ti-6Al-4V substrates, respectively. Rotating bending tests and uniaxial tests were conducted for investigating the effect of the thin and uniformly distributed hard CrN and TiN coatings on the fatigue and mechanical properties of Ti-6Al-4V substrate. During both tests, no coating spallation phenomenon was observed, which indicated that the hard coating bound well with the substrate. The fatigue test results showed that the fatigue strength of the coated sample was decreased in both the low- and high-cycling fatigue regimes compared with the uncoated Ti-6Al-4V substrate. Compared with the TiN coating, the CrN coating caused a more significant reduction on the fatigue property of the uncoated Ti-6Al-4V substrate due to its inferior plastic deformation capacity. Furthermore, the tensile test results showed that the coated sample had a relative higher ultimate strength, yield strength, and lower elongation compared with the uncoated Ti-6Al-4V substrate. This may be due to the fact that the hard coating could suppress the initiation of cracks, and so higher stress was needed for crack initiating. During the crack propagation period, the hard coating cracked at a relative higher velocity, which led to cracking of the ductile substrate and elongation reduction.

TiN/Ti coatings have great application potential in improving aero-engine server lives in a dusty environment. However, the damage behavior and mechanism of the coating and substrate under high impact speed and multi-direction loading conditions has scarcely been investigated. In this paper, TiN/Ti coatings were deposited on Ti6Al4V alloys by a magnetic filter cathode vacuum arc. Multi-directional impact tests were carried out by a gas gun system at, 45°, 60°, and 90° with a velocity of 330 m/s. The damage behaviors and mechanisms of the TiN/Ti coatings were investigated and revealed by researching the damage morphology, crack propagation, and stress distribution. The results show that plastic deformation occurs both in the coatings and the substrates under high speed impacting. Cracks extend vertically downward in the TiN layer first and are deflected at the Ti layer when the driving force is not enough. Circular cracks and radical cracks are found to form network cracks on the surface of the coating and the shear stress loaded by the particles, which drives cracks’ propagation is the main reason for the peeling off on the coatings.