Thermally sprayed Al 2 O 3 -TiO 2 coatings were in the area of interest over the last decade because they showed improved wear properties over conventional coatings. In this study, flexicord flame spray gun was used to deposit Al 2 O 3 -TiO 2 coatings at different spray parameters. The microstructural morphology variation and phase transformation of coatings were investigated. In addition, as one of the most important properties for ceramic coatings, hardness, solid particle abrasive wear resistance of coatings were measured before and after heat treated condition. Test results show that the higher mechanical properties and wear resistance by the heat treatment at elevated temperatures.

Low-pressure cold spray has been used as an innovative method to deposit metal matrix composite (MMC) coatings: boron carbide-nickel (B4C-Ni) and tungsten carbide-cobalt-nickel (WC-Co-Ni) composites. The coatings were studied using scanning electron microscopy, X-ray diffraction with Rietveld refinement, and acoustic emission-coupled four-point flexural test. Indentation fracture toughness tests were performed on the WC-Co-Ni coatings, only. The results showed that the composites had reinforcing particle volume fractions of 45.8 ± 0.3 vol.% and 22.7 ± 0.1 vol.% for the WC-Co-Ni and B4C-Ni MMC coatings, respectively. Flexural tests were used to evaluate the fracture strain of the composites. In these tests, the WC-Co-Ni composite failed by brittle facture at approximately 0.5% nominal strain. The B4C-Ni composite showed flexural behaviour similar to that of an unreinforced Ni matrix. These results suggest that there was insufficient B4C within the coating to affect significantly the ductile failure mode of Ni matrix. Post bending fracture analysis showed the presence of straight, continuous cracks on the WC-Co-Ni surface and the indentation fracture toughness of WC-Co-Ni was found to be 1.2 ± 0.2 MPa·m0.5. Discontinuous, random cracks were observed on the B4C-Ni surface. The quantification of these properties is essential in evaluating the performance of the low-pressure cold sprayings to determine their potential applications.

Properties and performance of the coating fabricated by wire arc spray process strongly depend on various factors including spray parameters and characteristics of both in-flight particle and splat. In this study, relationship between in-flight particle, splat formation and microstructure of the CrMoBW-Fe based nanocomposite coating fabricated by wire arc spray process were investigated. The Focus ion beam (FIB) milling was used to prepare a transversal cross-section of the in-flight particle and splat to be characterized by scanning electron microscopy (SEM) along with an energy dispersive x-ray spectroscopy (SEM-EDS). In addition, phase compositions were also analyzed by using x-ray diffractometer (XRD). The results revealed that size of the in-flight particles and splat morphology greatly influenced microstructure and properties of the coatings. In-flight particles were revealed a spherical-shape with a broad size distribution ranging from 0.8 to 115 µm at the average of 26 µm particle diameter. In-flight particles were well flattened on impact giving flower-shape splat with the average diameter of 100 µm. Flattening degree was found to be 3.8. Arc sprayed CrMoBW-Fe base nanocomposite coating showed very thin splat with fine lamella structure which implied that particles were fully molten upon impact onto substrate.

Plasma spraying ZrB 2 ceramic coating is considered as potential candidate method of Thermal Protective System. While the application of plasma sprayed ZrB 2 coating is restricted due to its oxidation. Therefore, it is important to study the oxidation behavior of the ZrB 2 material. In this research, oxidation behavior of the ZrB 2 ceramic, which achieve different density by using SPS and pressureless sintering, is studied to explain the oxidation behavior of plasma spraying ZrB 2 ceramic coating. The oxidation behavior of ZrB 2 ceramics is investigated using SEM, XRD and EDS. The ZrB 2 –based ceramic coating is gravely oxidized at 600°C, but the block ZrB 2 –based ceramics also possess excellent oxidation resistance above 1000°C. The density of ZrB 2 ceramics significantly increase when changing the sintering method from pressureless sintering to SPS. The high density has beneficial effect to improve the oxidation resistance of ZrB 2 ceramic, for there are few open pores channel in high density ceramics. The oxygen cannot diffuse to the inner through pores, as a result, the high density ceramics can only be oxidized from outside to inside progressively, unlike low density ceramics, whose surface and inner is oxidized simultaneously.

A commercial abradable coating AlSi-hBN was fabricated by atmospheric plasma spraying and was thermal aged at 450 °C in the atmospheric environment for 1000h. Thermal aging effect on coating abradability, hardness, bond strength and microstructure were evaluated. It was found that coating abradability increased obviously after 2h thermal aging and slightly decreased for extended thermal aging time. A sharp decrease in both coating hardness and bond strength were found after 2h thermal aging and a slow increase occurred with the extended aging time. Relationships between coating properties and microstructure were studied. Decomposition of organic binder and sintering of AlSi matrix metal generated by thermal aging were found to be reasons for coating properties changes.

The Ti 2 AlNb blade is used in high pressure compressor aero-engines to provide high thrust force at relatively light weight. A series of abradability tests was carried out on CuAlNi-graphite, NiCrAl-graphite, NiCrAl-bentonite, and NiCrFeAl-hBN abradable coatings rubbed against Ti 2 AlNb dummy blades with the maximum blade-tip velocity of 300 m/s at 500 °C. In consideration of the effects of an engine’s working conditions, some tests were conducted with incursion rate as the single variable. The scratched surfaces of the samples were observed by the stereoscopic optical camera, and a ratio of the blade wear to shroud incursion depth (IDR) was evaluated to characterize the abradability of coatings. The results show that NiCrAl-graphite and NiCrFeAl-hBN abradable coatings perform very well rubbed against the Ti 2 AlNb blade, and the blade-tip wear is not obvious after abradability tests.

This study investigates the relationship between in-flight particle characteristics, splat formation, and microstructure of CrMoBW-Fe base nanocomposite coatings produced by wire arc spraying. Focused ion beam milling was used to prepare transversal cross-sections of in-flight particles and splats for SE-SEM, EDS, and XRD analysis. The results show that particle size and splat morphology greatly influence the microstructure and properties of the coatings. In-flight particles were found to have a spherical shape with a broad size distribution ranging from 0.8 to 115 μm. The particles were well flattened on impact, resulting in flower-shaped splats with an average diameter of 100 μm. Splats were very thin with fine lamella structure, implying that the particles were fully melted at the time of impact.

This study demonstrates a new surface treatment for thermal barrier coatings that combines ultrasonic vibration and laser remelting and assesses its effect on crack distribution, surface morphology, and grain refinement. YSZ coating samples were vibrated at 20 kHz at different power levels while being irradiated by a Nd:YAG pulsed laser operated at 5.2 J and 6 J. SEM examination revealed a uniform distribution of segmented network cracks in treated samples, which are shown to play an important role in relieving stress and increasing strain tolerance in topcoat layers, thus improving fracture toughness and thermal cycle life. Another important finding is that visible ribbon-like loops induced by variations in surface tension were eliminated as a result of improved surface convection facilitated by ultrasonic vibration. At a vibration power of 520 W, coating surfaces were uniform and flat, but at 1300 W, undulations and trough geometries were observed. The results of XRD analysis indicate that tetragonal to monoclinic phase transformations are prevented when ultrasonic vibration power is greater than 780 W.

A comparative study was done on the structure and tribological properties of arc sprayed coatings and arc surfaced layers of TRIP steel. An iron alloy feedstock was used due to its ability to form a metastable austenite structure in both sprayed and surfaced layers that can be transformed to hard martensite by an applied external load. Microstructural and phase analysis and adhesive and abrasive wear tests were conducted to evaluate the coatings and surfaced layers. Differences in properties are explained based on input energy parameters.

The fatigue performance of conventional structural steel with an applied thermal barrier coating (TBC) was evaluated via cyclic bending. Tests were carried out for as-received and grit-blasted substrates as well as for samples with thermally sprayed bond coats and topcoats. Failure mechanisms were identified and changes in fatigue resistance were assessed based on results obtained for different loading amplitudes supplemented by fractographic analysis.

In the present study, X-ray microtomography is used to examine cold-sprayed tantalum splats on copper substrates. To resolve tantalum splats intermeshed with other splats of the same chemical composition, a contrasting medium of some sort is required. For this purpose, the feedstock powder is coated with an iron layer by means of fluidized-bed chemical vapor deposition. Experimental tests were coupled with finite element simulations to determine how stresses generated during the impact of a spherical iron-coated particle affect the integrity of the added contrasting layer.

Babbitt is used at tribology applications according to its low friction coefficient. Thermal spraying and pouring are widely used production processes of Babbitted parts. Comparative analysis of structure and wear properties of Babbitt layers produced by these technologies was done. Examples of typical arc sprayed Babbitted part's applications which were done at Mashprom are represented.

Microstructures and properties of electrical arc sprayed cored-wired coatings were investigated and compared in this work. Three types of cored-wired studied were WC-Ni, WC-Fe and nano WC-Fe The as-received cored-wire were characterized prior to be sprayed. In-flight particles were collected during spraying in order to reveal particle morphology and size distribution forming splats. Size distribution analysis of the filler particles showed that nanostructured WC-Fe had a comparable mean filler particle size with that of the WC-Fe and were larger than that of the WC-Ni. The difference in filler particle size of starting cored-wire was well correlated with the in-flight particle size produced. Nano WC-Fe cored wire coating had the lowest porosity and roughness compared to others with a comparable hardness to WC-Ni cored wire coating with rather different coating microstructures.

The characterization of thermal sprayed coatings is often limited to microstructural analysis to evaluate the coatings morphology. Indentation is commonly used to determine the mechanical properties of different kind of engineering materials. However, due to the complex structure of thermal sprayed coatings few results have been obtained so far. This is the second of two papers concerning the intrinsic mechanical properties of arc-sprayed WC-FeSiCMn coatings. In part 2 experimental nanoindentation tests and simulation results are compared. The experimental indentation tests show scattering in the force-deformation data due to the complex structure of the arc-sprayed coating which is investigated by means of an indentation test simulation. Based on these results the effective Young's modulus as well as further properties are identified. A general procedure is presented to predict the effective mechanical properties of different coating composites based on the microstructure, porosity and properties of the chemical composition after thermal spraying.

In cold spray, feedstock powders are accelerated by supersonic jet with solid phase and deposited onto substrate. Compare with the conventional thermal spray, the coatings have low porosity without oxidation and decomposition. This study examines the effect of the powder compressive strength of each particle on coating deposition characteristics using two types of Ni powders, manufactured in a different process, in cold spray. The result indicated that heat treatment reduced the powder compressive strength, and the decrease of the powder compressive strength was related to the increase of bond strength of particles and deposition efficiency. In addition, it was shown that the powder compressive strength has an influence of deposition mechanism.

High velocity oxyfuel (HVOF) thermal spraying and atmosphere plasma spraying (APS) were using to deposit a nickel aluminum (NiAl)/ hexagonal boron nitride (hBN) composite coating. The hBN powder was added to the Ni-5Al coatings to increase the lubrication property of the coatings. The hBN material was added to the NiAl alloy powder after either blending or ball milling to create the NiAl/hBN composite powders. The NiAl/hBN composite powders were than deposited as NiAl/hBN composite coatings. The velocity and temperature of the in-flight particles during thermal spraying were monitored using a DPV 2000 instrument. The morphology, microstructure and composition of the coatings and powders were analyzed. The coatings with the best lubrication and most uniformly deposited microstructure were formed when the NiAl/hBN coatings were deposited using the atmosphere plasma spraying method.

The brittleness of intermetallic compounds severely hampers their appliance in industry as high temperature structural materials. In order to make use of their good qualities and avoid the influence of their disadvantages, this paper put forward another method on the application of intermetallic compounds--using as coatings on the surface of structural materials. Lots of experiments have been done on Fe-Cr-Al intermetallic compounds and excellent coatings were acquired by high temperature in-situ reaction process. The coating is compact and bonded well with substrate. And the result of experiment shows that it has wonderful corrosion resistance to molten zinc.