Yttria stabilized zirconia coatings (YSZ) have received great attention as a good candidate for thermal barrier coatings (TBCs). However, the grain growth and phase transformation, within applied coatings particularly under temperatures higher than 1473 K limit its further applications to great extent. In our present study, in order to develop better understanding of aforementioned phenomena and explore effective methods to conquer this challenge, TBCs using traditional and La 2 O 3 modified YSZ powders were deposited by atmospheric plasma spraying and their microstructures were investigated. Results show that the La 2 O 3 addition can effectively alleviate the grain growth of coatings under high temperature.

In this study, three different types of Al 2 O 3 coatings were prepared by atmospheric plasma spraying. Some physical properties of these coatings were measured. Microstructure and wear morphologies of coatings were investigated by scanning electron microscopy (SEM) and optical microscopy (OM). The tribological behaviour of various coatings against stainless steel using a block-on-ring configuration were investigated in terms of the microstructure, physical properties especially the thermal diffusivity of coatings and the evaluation of tribological heat. Results revealed that the wear resistance of coatings used in this work showed a high dependence on their thermal diffusivity rather than other properties such as porosity, microhardness and bond strength: the higher the thermal diffusivity of a ceramic coating, the better is its wear resistance.

In the present work, silicon coating was deposited using air plasma spraying technology. The temperature and velocity of particles in the plasma spraying were measured. The phase composition and microstructure of the coating was studied. And some mechanical and thermal properties of the coating were evaluated.

In the present study, Al 2 O 3 coatings were deposited by plasma spraying using feedstock of different particle sizes. The effects of particle size on their velocity and temperature in the plasma jet, the microstructure and properties of the coatings were investigated. The results revealed that in view of the smaller inertia effects and lower heat capacity, the smaller particles can be easily accelerated and heated, and have higher in-flight velocity and temperature, which contributed to produce a denser coating with lower porosity and higher mechanical properties. It was also found that the coating deposited using the finest starting powder has the lowest thermal diffusivity. This may be reasonably correlated with the microstructural characteristics. In addition, the coating manufactured using the intermediate feedstock in terms of particle size (D50 of 19.3µm) exhibited the highest wear resistance.

Calcium oxide stabilized zirconia coatings have been deposited onto Ti-6Al-4V substrates by means of atmospheric plasma spraying and incubated in the simulated body fluid for different periods of time to investigate the formation of apatite on their surface. The phase composition and microstructure of the coatings before and after immersion were examined by scanning electron microscopy and X-ray diffraction. The results obtained showed that apatite can be formed on the coating soaked in SBF solution, which indicated that calcium oxide stabilized zirconia possessed good bioactivity.

Titanium/dicalcium silicate composite coatings with different ratios (weight ratios as Ca 2 SiO 4 : Ti = 3:7, 5:5, 7:3) were prepared by plasma spraying. Effects of titanium addition on coating properties, such as bonding strength, Young’s modulus and dissolution in simulated physiological environment, were studied. Results showed that the bonding strength between coating and Ti-6Al-4V substrate increased with increase of titanium content in the composite coatings. It was explained by the narrowed dissimilarity of thermal expansion coefficients between the coatings and substrates. Degradation of mechanical properties after immersion in simulated body fluid was also studied. The dissolution of dicalcium silicate in the composite coatings resulted in the decrease of bend strength and Young’s modulus of the coatings in the simulated physiological environment. The higher titanium content in the composite coatings, the stabler are the composite coatings in the physiological environment.

Plasma sprayed ceramic coatings have been widely applied in modifying surface properties of metal components. They are useful to prevent various types of wear, corrosion, erosion and thermal degradation, thereby extending components service life and reducing the need for expensive and repetitive maintenance. The durability and functionality of plasma sprayed ceramic coatings is critically dependent on the adhesion between the ceramic coating and the underlying substrate as well as the cohesion between splats. In this work, both nanostructured and conventional Al 2 O 3 coatings were prepared by atmospheric plasma spraying technology (APS). For each feedstock, four kinds of coating samples deposited under different spraying parameters were designed, and moreover, seven groups of conventional coatings with different thickness were deposited under the same spraying parameters. Adhesion/cohesion of the plasma sprayed Al 2 O 3 coating samples were evaluated by scratch testing. The results obtained reveal that the spraying parameters have strong influences on the microstructure of plasma sprayed Al 2 O 3 coatings, which in turn influence their properties including deposition efficiency, porosity, microhardness as well as adhesion/cohesion.

In this work, a TiO 2 coating with nanostructured surface was obtained through plasma sprayed nano-sized TiO 2 powder. Its bonding strength onto Ti-6Al-4V substrate is high up to 38 MPa. At same time, we have successfully improved the bioactivity of plasma sprayed TiO 2 coating with nanostructured surface using hydrogen ion implantation and UV illumination. Bone-like apatite can form on the surface of the post-treated TiO 2 coatings after they are soaked in simulated body fluid for a period of time. Introduction of surface bioactivity (bone conductivity) to plasma-sprayed TiO 2 coatings which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys makes them more superior than many current biomedical coatings such as plasma-sprayed hydroxyapatite.

In this paper, nanostructured layers of zirconium and aluminum oxide are produced by atmospheric plasma spraying. The layers are characterized using SEM, TEM, X-ray phase analysis, and hardness measurements, the results of which show that hard, dense nanostructured oxide layers were achieved. Paper includes a German-language abstract.

Recent developments in the field of plasma sprayed ceramic coatings at Shanghai Institute of Ceramics (SIC) are presented. Nano-titania and nano-tungsten carbide coatings were prepared. Their structure and properties were detected. The super hard B 4 C coating was deposited by APS. The physical and mechanical and anti-irradiation properties of B 4 C were measured. Wollastonite coating was deposited and its bioactivity has been tested. The results obtained indicated that (1) nano-titania coating possessed porous structure and unique electric properties; (2) nano-WC-Co coating exhibited notable wear resistance; (3) B 4 C coating was excellent irradiation resistance and (4) the carbonate-containing hydroxyapatite was formed on the surface of wollastonite coating, which indicated that this coating has excellent bioactivity.

This article describes a method of preparing bioactive and porous titanium coatings on titanium-based substrate using vacuum plasma spraying and chemical treatment in alkali solution. The porous titanium coating was fabricated in two-layer structure. The bond strength, average porosity and roughness (Ra) of the porous titanium coating are 55MPa, 30% and 21µm, respectively. The chemical treatment of as-sprayed titanium coatings was carried out in 5.0M NaOH solutions at 40 °C for 24h. The surface morphology and structure of the porous titanium coating before and after chemical treatment were examined by SEM and laser Raman spectroscopy. The treated titanium coating was immersed into SBF to evaluate its bioactivity by examining apatite formation on its surfaces. It was observed by SEM and TF-XRD that apatite was formed on the surface of the treated titanium coating after immersion in SBF. The spherical aggregates gradually grew large by consuming calcium and phosphate ions in SBF and covered the surface with increase in soaking time. Incorporation of CO 3 2- ions into apatite crystal lattice was revealed by FT-IR. The results obtained indicated that net-like sodium titanate formed due to NaOH attack was responsible for apatite nucleation and growth. It is concluded that vacuum plasma spraying and subsequent chemical treatment is an effective way to produce bioactive and porous titanium coatings.

To improve the bonding strength of HA coating, several HA-based composite coatings (HA/Ti, HA/ZrO 2 HA/ZrO 2 SiO 2 and HA/NiCr composite coatings) have been fabricated via atmospheric plasma spraying. The bonding strengths of fabricated specimens were tested by ASTM C-633 method. The bioactivity of composite coatings was evaluated by examining carbonate-containing apatite formation on their surfaces in simulated body fluid (SBF). In vitro cell cultures were carried out to examine the biocompatibihty of composite coatings. The results obtained revealed that the addition of metal or ceramics in HA improved the bonding strength of coating significantly except HA/ZrO 2 -SiO 2 composite coating. In SBF test, all of these four coatings were covered by carbonate-containing apatite after immersed in SBF, indicating good bioactivity for composite coatings. The results of cell cultures produced the testimony of excellent biocompatibihty for the coatings except that HA/NiCr composite coating possessed cytotoxicity. By comprehensive survey of bonding strength, bioactivity and biocompatibihty, HA/Ti and HA/ZrO 2 composite coatings were candidates of prospective biocoatings.