In this study, hydroxyapatite (HA) coatings were deposited on stainless steel by suspension plasma spraying. Coating samples and suspensions were examined by means of electron microscopy, XRD analysis, and FTIR and Raman spectroscopy. The results show that the coatings are porous and nanostructured with no impurity phases when low H 2 flow rates are used. They also contain a significant amount of OH - and CO 3 2- , which facilitates the formation of well-crystallized HA and improves bioactivity and compatibility in implant applications.

In this paper, copper coatings were deposited on a metallic substrate by means of multi-function micro-plasma spraying under different processing parameters. The microstructure and phase structure of copper coatings were investigated using a scanning electron microscope and X-ray diffraction, bonding strength were tested by an electron tensile tester, droplet impinging and flattening on a flat substrate surface and the residual stress after solidification were studied numerically. The experimental results show that the density of copper coatings was improved with increasing plasma power and operating gas flow, and this copper coating possessed high adhesion strength and low residual stress, still without obvious oxidation. This spraying system extends the application field of tradition plasma spray. Through changing the processing parameters, materials with different melting points, even as low as copper can be produced.

In this paper, the effects of ceria addition to HVOF thermal sprayed NiAl intermetallic coatings were investigated through micro-indentation, thermal shock testing, and microstructural analysis techniques including SEM with EDX, and XRD analysis. It has been found that the addition of ceria to NiAl coatings reduces the tendency of brittle peeling during thermal spraying. This reduction in peeling is presumably due to the improved wetting of the substrate by the molten coating material, which ultimately leads to better coating adhesion. The addition of ceria also resulted in higher coating hardness and elastic modulus as determined by micro-indentation. The coatings containing ceria also exhibited significant increases in thermal shock resistance when compared with that of the pure NiAl coatings. The possible mechanisms responsible for the improvement of the above mentioned properties upon the addition of ceria are also addressed in this paper.

One of the methods used for the evaluation of coating adherence consists of determining an apparent interfacial fracture toughness through interfacial indentation in the cross-section of the coated system. In the present paper the interfacial crack propagation in a thermal spray coated system, during interfacial indentation test, was studied by finite element method. A Vickers indenter was applied at the coating/substrate interface to perform indentation test. In order to simulate the cracking, an initial semi-circular crack lying at the interface between the substrate and the coating was considered. Since the cracks resulting from interfacial indentation test have been reported to have a semi-circular shape, the crack was forced to advance by a uniform distance normal to the crack front in the plane of interface at each step of calculation. In these conditions it was shown that the interfacial crack has a mixed fracture mode. An apparent interfacial fracture energy Jca was calculated by this method to evaluate the interfacial adhesive toughness. The model was applied to study the crack propagation at the interface between a Cr 3 C 2 -NiCr HVOF coating and a grey cast iron substrate. A reasonable agreement between the calculation results and reported experimental data was found.