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The use of advanced thermal spray technology for surface modification of aluminum alloy parts for automobiles can greatly improve the surface properties and service life of the parts while saving resources and reducing environmental pollution. In this paper, a Ni60A coating was prepared on the surface of aluminum alloy 109 (ZL109) by supersonic plasma spraying (HEPJet). The spraying process parameters were optimized based on the response surface methodology (RSM). The effects of the main factors such as spraying power, spraying distance, and Ar flow rate on the porosity and microhardness of the coating were analyzed by the Box–Behnken method (BBD). The response surface of the porosity and microhardness of the coating was constructed by establishing the appropriate mathematical model. The response surface of porosity and microhardness of the coating was constructed by establishing a relevant mathematical model. The results show that the established mathematical model is reliable, and the spray power has the greatest influence on the porosity and microhardness of the coating. The optimal porosity and microhardness of the coating predicted by the model are 0.85% and 971.1HV0.1, respectively, which is close to the experimental results. The porosity and microhardness of the coating measured by the experiment are 0.87% and 959.8HV0.1, respectively. The coatings prepared with optimal parameters have good compactness, small porosity, and high hardness. [ABSTRACT FROM AUTHOR]

Herein, we have deposited Cr/CrN/Cr/CrAlN multilayer coatings with various modulation ratios on TC11 alloy substrate using cathodic arc system. The influence of various modulation ratios on microstructure and Al 2 O 3 sand erosion behavior of coatings is systematically studied. Results reveal that the coatings are about 200 nm per cycle and total thickness is 8 μm. Five groups of coatings exhibit high hardness (>3000 HV 0.025). The coating with modulation ratio of 12 adhesion can reaches 55 N. The residual stress increases with the decrease of the modulation ratio, but the increase is generally low (less than −2 GPa). In addition, according to sand erosion test, it is found that sand erosion resistance of multilayer coating is significantly around 5 times higher than TC11 alloy matrix. The erosion morphology shows that a large number of irregular cracks and layered spalling appear on the surface of the coating, indicating that the cracks are constantly initiated under the continuous impact of the sand and gravel，and finally gather together and then spalling. Moreover, dynamic response and stress field of the coating under the impact of single sand (Al 2 O 3) are studied by numerical simulations. It is determined that coating cracking is caused by high tensile stress under CrAlN layer. In addition, according to crack propagation morphology and influence of different interfaces between multilayered structures on crack tips, propagation/termination mechanism of cracks is analyzed in detail. Cracks are easy to initiate in hard CrAlN layer and consume a lot of energy after propagating into soft Cr layer, thereby ending at next soft and hard interfaces. These results provide experimental and theoretical support for the study of high tenacity and anti-erosion coating. [ABSTRACT FROM AUTHOR]

A dense environmental barrier coating (EBC) was designed via aluminum infiltration into open pores or cracks to eliminate premature coating failure induced by the rapid permeation of oxidants through these pores. The water vapor corrosion performance of the EBC with and without aluminum infiltration was investigated at 1350 °C for 300 h under flowing 50%H 2 O–50%O 2 gas. The infiltrated coating exhibited decrease silicon loss by more than 80%, almost no phase decomposition, and no continuous thermally grown oxide (TGO), furthermore, TGO thickness at the crack-root decreased by ∼90%. The excellent resistance is primarily attributed to the channel pores being filled with aluminum, which eliminates the rapid permeation of oxidants. In addition, a continuous refractory ytterbium aluminum garnet (YbAG) layer was formed in situ on the EBC surface, this layer exhibited sufficient stability in steam, rendering the EBC less permeable to oxidants. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the Metal-rich phase Chromium Aluminum (CrAl)/Ceramic phase Chromium Aluminum Nitride (CrAlN) multi-layer coatings were prepared by Arc Ion Plating (AIP). The micro-structure and phase composition of CrAl/CrAlN multi-layer coatings were characterized, and the microstructure, mechanical properties, residual stress and fracture toughness of the coating were emphatically analyzed. It has been found out that the residual stress of the multi-layer coating was only −0.932 ± 0.065 GPa, which was significantly lower than that of the mono-layer coating for −1.569 ± 0.093 GPa. At the same time, it was also found that the preferred growth orientation of the coating changed from a mono-layer (111) to a multi-layer (200) crystal plane. The hardness of the multi-layer (22.74 ± 0.57 GPa) is slightly lower than that of the mono-layer (24.92 ± 0.5 GPa), and the adhesion strength (46.2 ± 3.8 N) is obviously higher than that of the mono-layer (37.4 ± 2.4 N), and the fracture toughness is also higher (8.7 ± 0.8 MPa m1/2). In addition, the mechanism of crack initiation and propagation in stress-induced coatings was studied in detail on the basis of the structure of micro-nano CrAl/CrAlN multi-layer coatings. [ABSTRACT FROM AUTHOR]

In this work, a 12 μm Cr/CrN/Cr/CrAlN erosion-resistant multilayer coating was prepared by arc ion plating. According to the application conditions of high-temperature changing environment, the high-temperature thermal shock performance and erosion resistance of the coating were studied. The results show that the Cr/CrN/Cr/CrAlN coatings show no change after thermal shock up to 700 °C. After thermal shock at 900 °C, the surface shows discolouration and wrinkling, and the nitride phase in the coatings disappears and Cr 2 O 3 and α-Al 2 O 3 phases appear. The hardness of the coating after thermal shock is reduced from 3658.57 Hv to 1930.96 Hv, and the adhesion strength is reduced from HF1 to HF4. The erosion rates of the coatings after thermal shock at room temperature, 300 °C, 500 °C and 700 °C do not vary significantly, and are within 1 mg/g at 30° and 90°. The coating is completely unprotective when the thermal shock temperature reaches 900 °C, reaching 2.731 mg/g at 30° and 4.832 mg/g at 90°. It shows that the coating has an anti-erosion protection effect within 700 °C, but the coating has completely failed after a thermal shock at 900 °C and has no protective effect. • Designed and prepared a 12 μm Cr/CrN/Cr/CrAlN multilayer coating. • Coating produces thermal expansion mismatch stress and oxide growth stress at high temperature. • The effective temperature of the coating against erosion protection reaches 700 °C. [ABSTRACT FROM AUTHOR]

In this study, we deposited CrNx/CrAlN multilayer coatings with different modulation periods on TC4 titanium alloy substrates via cathodic arc deposition. The effects of the different modulation periods on the microstructure, mechanical properties, erosion resistance, and fracture failure mechanism of the coatings were studied. The results show that the multilayer coatings exhibit a dense structure, with the CrNx layer being mainly composed of the CrN (200) and Cr 2 N (111) phases and the CrAlN layer being mainly composed of the CrN (111) and CrN (200) phases. The comprehensive mechanical properties of the multilayer coating with a modulation period of 200 nm are the best: The hardness is 3306 HV, the bonding force is 50.0 N, the crack propagation resistance is 483, the residual stress is the smallest, and the erosion resistance is the best. In the process of coating fracture failure, the CrAlN hard layer is mainly wear-resistant, while the CrNx metal-rich ductile layer mainly absorbs the fracture stress and undergoes a ductile–brittle transition, which eventually results in brittle fracture and layered peeling failure. • Designed and prepared the CrNx/CrAlN multilayer coatings with different modulation periods. • When the modulation period was 200 nm, the comprehensive mechanical properties of the coating were the best. • After eroded, the rich metal layer absorbs the fracture stress, undergoes a ductile-brittle transition, and exfoliates. [ABSTRACT FROM AUTHOR]

In this paper, a 16 µm CrN/CrAlN multilayer coating is prepared on the titanium alloy surface via arc ion plating. Since titanium alloys are susceptible to wear in a high-temperature environment, high-temperature wear performance and mechanism after coating are investigated. The results show that the friction coefficient of the CrN/CrAlN multilayer coating decreases with an increase in temperature during wear tests at room temperature, 300 ℃, 500 ℃, and 700 ℃. Moreover, the friction coefficient decreases from 0.9 at room temperature to 0.4 at 700 ℃. The wear rate increases with the temperature, more specifically from 1.32 × 10−5 mm3/(N·m) at room temperature to 6.45 × 10−5 mm3/(N·m) at 700 ℃. [ABSTRACT FROM AUTHOR]

Diamond-Cu composites have been considered to be the next generation of electronic packing materials. One of the key stumbles for such an application is the joining problem between diamond-Cu composites and other materials due to the poor wettability of the diamond particles in the composites. In order to overcome this hurdle, pure Cu powder was thermally sprayed onto diamond-Cu substrate by low-temperature high-velocity oxygen fuel spraying process. Microstructure and some fundamental properties of the coating obtained were systematically investigated, and morphologies of the single splat deposited on the diamond-Cu substrate were also observed. The splats obtained have good adhesion with the substrate as fine particles flattened sufficiently, while the coarse particles were significantly deformed. The coating was quite dense with porosity lower than 1%, oxygen content under 0.5% and thermal conductivity about 266 Wm K and still remained on the diamond-Cu substrate after 50 thermal shock cycles between 300 °C and water bath at room temperature. Meanwhile, the solderability of the coating was significantly improved. Therefore, Cu coating deposited on diamond-Cu substrate by low-temperature high-velocity oxygen fuel spraying process can be beneficial in electronic industry assisting with soldering and improved wettability for joining of other materials. [ABSTRACT FROM AUTHOR]

In this study, CrN and CrAlN coatings were deposited on the surface of aerospace titanium alloys using the arc ion plating technology to investigate the effect of the microstructure of the coatings on the mechanical and erosion resistance properties. The cross-sections of the coatings were observed by Scanning Electron Microscope(SEM), the microstructures were characterized by Transmission Electron Microscope(TEM), and the crystalline structures were tested by X-ray diffraction (XRD); furthermore, the hardness of the coatings was determined by a micro-Vickers hardness tester, the film-base bond strength was measured by a scratch tester, the change in curvature was measured by laser scanning and the residual stress was calculated. The fracture mechanism of the coating was elucidated by simulating the fracture pattern of the cross-section of the erosion crater. The results indicated that the thicknesses of the CrN and CrAlN coatings were almost the same, but the number of large particles on the surface of the CrAlN coating was higher. Both sets of coatings exhibited a nanocrystalline structure with a grain size of around 10 nm. Due to the doping of the Al element, the CrAlN coatings exhibited a hardness of 2846 HV and a higher residual stress of −1.831 GPa. Both the CrN and CrAlN coatings showed lower erosion rates than the titanium substrate at 30° and 90° angles of attack. The results of finite element simulations indicated that the more ductile CrN coating exhibited a better stress absorption capacity, and a typical brittle fracture failure mechanism was observed for both sets of coatings. • CrN and CrAlN coatings with good erosion resistance were obtained. Compared with the titanium alloy substrate, the erosion rate of the coated sample is only 1/8 of the titanium alloy substrate at 30°, and only 1/3 of the titanium alloy at 90°. • The erosion fracture process of the hard coating was explored, in which the cracks were mainly in the direction perpendicular to the film-base interface, and were easily deflected by stress concentration at the microparticles and the interface. • Both CrN and CrAlN coatings are typical brittle fracture failure mechanisms, but the tougher CrN coating has better stress absorption capacity. [ABSTRACT FROM AUTHOR]