High Efficiency Supersonic Plasma Spraying Research Articles

Study on Properties of Potassium Sodium Niobate Coating Prepared by High Efficiency Supersonic Plasma Spraying

In order to realize the construction of environmentally friendly potassium sodium niobate ceramic coating on metal surface, potassium sodium niobate ceramic coating was prepared by supersonic plasma spraying technology. The morphology, element extension and phase structure of such coating were investigated. The dielectric and ferroelectric properties were also analyzed. The results show that the coating has good quality and tetragonal phase structure. When test frequency ≥ 2 MHz, the dielectric constant is stable at about 300, and also dielectric loss is stable at about 0.05. The coating exhibits good hysteresis loops under different applied electric fields. When the applied electric field is 16 KV/cm, residual polarization value of as-prepared coating reaches 17.02 μC·cm−2.

Comparison of Dry Sliding Tribological Behavior of Nanostructured Al2O3–13 wt% TiO2 Coatings Prepared by High-Efficiency Supersonic Plasma Spraying and Atmospheric Plasma Spraying

Abstract Plasma-sprayed ceramic coatings have been widely used in friction and wear protection of mechanical parts. In this paper, the nanostructured Al2O3–13 wt% TiO2 coatings were prepared by high-efficiency supersonic plasma spraying (HESP) and atmospheric plasma spraying (APS), respectively. The surface and section morphology of the coatings were observed by scanning electron microscopy (SEM). The phase composition of the coatings was analyzed by X-ray diffraction (XRD). The dry sliding friction properties of the coatings were tested on UMT-3 friction and wear testing machine. The results show that after plasma spraying, a large amount of γ-Al2O3 phase appears, while the TiO2 phase almost disappears in the coatings; compared with APS, the coatings sprayed by HESP have fewer defects and better coating quality; under dry friction condition, the steady-state friction coefficient of the coatings sprayed by HESP and APS all decreases with the increase of load, and the wear volume all increases with the increase of load. When the load is more than 40 N, wear volume of the coatings sprayed by APS is basically twice that of HESP; the wear mechanism of the coatings sprayed by HESP is the laminar cracking, peeling off and the adhesive wear.

Microstructure and Corrosion Behavior of Aluminum Coatings Prepared by High-Efficiency Supersonic Plasma Spraying and Oxygen–Acetylene Flame Spraying

Thermal spraying aluminum coatings have been widely used in the corrosion protection of mild steel in seawater. In this study, high-efficiency supersonic plasma spraying (HESP) and oxygen–acetylene flame spraying (FS) were used to prepare aluminum coatings. The micromorphology of the coatings was analyzed by a scanning electron microscope equipped with an energy-dispersive x-ray spectrometer. The phase identification of the coatings was conducted by an x-ray diffractometer. The Vickers hardness and bonding strength of the coatings were measured by an HMV-2000 Vickers hardness tester and MTS809 universal tensile tester. The corrosion resistance of the coatings was tested by an IM6ex electrochemical workstation. The results show that the aluminum coatings prepared by HESP have a denser structure, higher microhardness, higher bonding strength, and better corrosion resistance than those prepared by the traditional FS. After 480-h immersion in 3.5 wt.% NaCl solution, a dense corrosion product formed on the surface of aluminum coatings prepared by HESP prevents further corrosion of the coatings, but the aluminum coatings sprayed by FS demonstrate a serious pitting phenomenon.

Microstructures and Wear Resistance of Al-25 wt.%Si Coatings Prepared by High-Efficiency Supersonic Plasma Spraying

Hypereutectic Al-Si alloy is an ideal surface strengthening material for aluminum alloy cylinder body. However, the coarse eutectic silicon phase and primary silicon particles in Al-Si alloys prepared by traditional methods lead to poor mechanical properties of the alloys, and the high cost of preparation limits the practical application of hypereutectic Al-Si alloys. In this study, Al-25 wt.%Si coatings were prepared on substrate 7075 by high-efficiency supersonic plasma spraying (HESP). The micromorphology, Vickers hardness, bonding strength and wear resistance of the coatings were measured and characterized by experiments. The results show that the Al-25 wt.%Si coatings prepared by HESP have a denser structure, and the primary silicon phase in the coatings is refined. The hardness of the coatings is 235 HV0.1, and the bonding strength between the coatings and the substrate is 44.1 MPa. The wear rate of the coatings is reduced by 20 times compared with that of the substrate, and the wear mechanism is mainly adhesion wear and oxidation wear.

Process optimization and coating properties of aluminum coating prepared by supersonic plasma powder feeding based on response surface

This paper adopts High Efficiency Supersonic Plasma Spraying (HEPJet) to produce aluminum coating under the condition of large powder delivery. Based on the Box-Behnken-Design (BBD) design in Response Surface Method (RSM), the interaction of Ar flow, power and spraying distance with the deposition efficiency and microhardness of aluminum coating was analyzed, and the spraying parameters of aluminum coating prepared by supersonic plasma powder feeding were optimized. The coating performance was analyzed by means of electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the established quadratic equation model is reliable and the influence of spraying distance coating on deposition efficiency and microhardness is greatest. The parameters of spraying with large powder delivery were as follows: argon 200 L/min, power 50 kW, spraying distance 40 mm, and powder delivery amount 150 g/min. Moreover, the aluminum coating prepared by HEPJet has poor density, large porosity and severe oxidation, which provides reference value for the subsequent research on the preparation of aluminum coating by HEPJet.

Microstructural design and oxidation resistance of CoNiCrAlY alloy coatings in thermal barrier coating system

This paper aims to improve the oxidation resistance of plasma-sprayed CoNiCrAlY coatings by optimizing microstructure. A series of coatings that contained 22.5 ± 2.3%, 35.4 ± 2.2%, and 57.8 ± 2.5% unmelted particles were fabricated by a high efficiency supersonic plasma spraying (SAPS) system. Experimental results showed that the β phase mainly existed in the unmelted particles, and its content increased with increasing the content of unmelted particles. The coating that contained 35.4 ± 2.2% unmelted particles showed the best oxidation resistance. An accurate numerical model obtained from molecular dynamics simulation was used to explain the experimental results. Our study confirmed that an appropriate amount of unmelted particles can improve the oxidation resistance of CoNiCrAlY coating.

High performance nanostructured ZrO 2 based thermal barrier coatings deposited by high efficiency supersonic plasma spraying

In this paper, the nanostructured zirconia (ZrO 2) based thermal barrier coatings (TBCs) deposited by high efficiency supersonic atmospheric plasma spraying (SAPS), were described. The phase composition, microstructure, thermal conductivity and thermal shock resistance of as-sprayed coating were studied. The results revealed that the as-sprayed coating was composed of tetragonal zirconia and consisted of some unmelted nanoparticles (30–50 nm) and nanograins (60–110 nm), and the latter was the main microstructure of the coating. The nanograins and homogeneously distributed micro-cracks of coating resulted in not only low thermal conductivity, but also high thermal cycling lives. Besides, the failure process of coating during thermal cycles was also investigated in the present work.

Microstructural Study of Nanostructured ZrO<sub>2</sub> Based Thermal Barrier Coatings Fabricated by High Efficiency Supersonic Plasma Spraying

In this paper, the microstructure of nanostructured zirconia (ZrO2) based coating fabricated by newly developed process, high efficiency supersonic atmospheric plasma spraying (SAPS), is studied. The velocity and surface temperature of in-flight particles during spraying were monitored by on-line system and the microstructure and phase composition of the as-sprayed coating was characterized with SEM, TEM and XRD. Meanwhile, the bonding strength between the top coating and bond coating was measured. The results showed the average in-flight velocity of YSZ particles in SAPS was about 430m/s, which was much higher than that of conventional atmospheric plasma spraying (APS). The as-sprayed coating was composed of well-adhered fine lamellar structures with thickness of 1-4μm. The desirable structure was attributed to higher impact velocity of in-flight particles during SAPS process, resulting in the improvement of flattening degree of molten particles. Meanwhile, the SAPS-YSZ coating exhibited a bimodal distribution with small grains (30-50nm) and large grains (60-110nm), the latter was the main microstructure of the coating. In addition, it was found that the monoclinic zirconia existing in the original powders transformed into tetragonal phase after plasma spraying and the bonding strength of as-sprayed coating was as high as 46±3MPa. The high efficiency supersonic plasma spray, which offers some unique advantages over the conventional plasma spraying process, is expected to be potentially used to deposit a wide variety of nanostructured coatings at lower cost.