Phase composition and microstructure of hydroxyapatite (HA) significantly affects the biological and mechanical properties of final hydroxyapatite (HA) coating. In the present study, HA coatings were deposited on Ti-6Al-4V by micro-plasma spraying (MPS) using different spray parameters. The influence of spray parameters on the composition and microstructure of the coatings were investigated. To understand the formation mechanism of HA coatings, the in-flight particles and splats were examined as well. The morphologies of coatings surface, cross-sections, initial powder, in-flight particles and splats were characterized by scanning electron microscopy (SEM). Xray diffraction (XRD) was employed to analyze the phase composition. Three typical HA coatings were fabricated. The results indicated that the coating composition and microstructure were tightly related to the melting state of inflight particles. And this was influenced by the spraying parameters. The formation mechanisms of these coatings were discussed.

In this work, micro-plasma spraying is used to produce hydroxyapatite coatings on Ti-6Al-4V substrates. To understand coating formation mechanisms, in-flight particle velocity and surface temperature were monitored under different spraying conditions. XRD measurements show that the resulting coatings have a high degree of crystallinity with little amorphous or metastable phases. Some of the coatings were also found to have a uniformly distributed columnar structure, corresponding to a strong (002) texture and excellent stability in Hanks’ salt solution even after 14 days of immersion.

Nanostructured WC-CoCr powder was prepared and deposited on carbon steel substrates by HVOF spraying. The coatings obtained were characterized based on phase constitution, elemental distribution, and microstructure as well as corrosion and sliding wear behaviors. X-ray diffraction was used to identify the main phase constituents and EDS analysis revealed the distribution of Co and Cr in the coating. The mechanisms involved in the formation of microstructure are discussed along with the effects of Cr on coating performance.

A nanostructured WC-CoCr coating was fabricated by HVOF spraying using a new type of WC-CoCr powder in which the CoCr exists in the form of a metallic compound. The CoCr powder constituent was prepared by induction melting and mechanical milling. It was then combined with a WC-Co composite nanopowder and the mixture was agglomerated by spray drying and heat treating. The powders and coatings produced were characterized by means of XRD, EDS, and BSE analysis, nanoindentation testing, and potentiodynamic polarization studies. The results show that the presence of the intermetallic CoCr compound makes nanostructured WC-CoCr coatings harder and much more corrosion resistant than conventional WC-Co-Cr coatings in which Cr exists as an unalloyed metal.

In this paper, the nanostructured zirconia thermal barrier coatings were prepared on GH3030 high temperature alloy surface by plasma spraying process. The nanostructured agglomerated ZrO 2 feedstock was used as initial powders, and the NiCoCrAlY alloy as bond coating material. The relationship between bonding strength and spray current, secondary gas flow and spray distance were analyzed. The optimum parameters were acquired by orthogonal experimental design methods. The microstructures and phase structures of nanostructured zirconia thermal barrier coating were investigated thoroughly by SEM, TEM and X-Ray.

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.

In this work, 30wt% calcium silicate, including wollastonite and dicalcium silicate, were mixed with 70wt% ZrO 2 , respectively. The composite powders were deposited onto Ti-6Al-4V substrates to prepare wollastonite/ZrO 2 and dicalcium silicate/ZrO 2 composite coatings using plasma spraying technology. The bioactivity of coatings was evaluated using simulated body fluid soaking test. After the composite coatings were soaked in simulated body fluid for a certain period, apatite was formed on the surface of the wollastonite/ZrO 2 and dicalcium silicate/ZrO 2 composite coatings. In addition, the ZrO 2 in composite coatings may protect the calcium silicate in the coatings from dissolving in simulated body fluid.

In this paper, nano-structured TiO 2 coatings have been successfully deposited onto titanium alloy substrates by atmospheric plasma spraying technology using optimized plasma parameters. A chemical treatment method was employed to induce bioactivity on the TiO 2 surface. The bioactivity of as-sprayed and chemical treated TiO 2 coatings were evaluated by investigating the formation of apatite on their surface after they were soaked in simulated body fluids (SBF) for a period of time. Microstructure and the phase composition of the as-sprayed coating and apatite were analyzed by Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDS). The results obtained indicate that as-sprayed TiO 2 coating consists of rutile, anatase and suboxide such as Ti 3 O 5 . The surface of nano-TiO 2 coating is covered by nano particles of about 50nm in size. The bonding strength of TiO 2 coating with Ti alloy substrate is as high as 40 MPa. The corrosion resistance performance of nano-coating in SBF is better than that of Ti-6Al-4V alloy. The surface of as-sprayed TiO 2 coating can not induce bone-like apatite formation. Chemical treatment, such as acid and alkali, can improve bioactivity of TiO 2 coating surface.

In this paper, the Al 2 O 3 , ZrO 2 , TiO 2 , wollastonite, dicalcium silicate and their composite coatings were deposited onto Ti-6Al-4V substrates by an atmosphere plasma spray system. The rat osteoblasts were seeded onto the surface of the coatings to evaluate the growth behavior of osteoblasts on different implant materials. Scanning electron microscopy was used to observe the morphologies of the osteoblasts seeded on the surface of the coating for different time. The SEM observation indicated the osteoblasts are difficult to survive and proliferate on the Al 2 O 3 coating surface. Osteoblasts can survive and proliferate slowly on the TiO 2 and ZrO 2 coating surface. Osteoblasts grow and proliferate very well on the surface of the wollastonite and dicalcium silicate coating, which present the two coatings possess excellent cytocompatibility. The addition of wollastonite and dicalcium silicate into ZrO 2 and TiO 2 can improve their cytocompatibility.

This paper describes some of the problems solved in the development of a mold-making process in which the molds are coated using a 2mm wire arc-spraying system. A water solution release agent has been chosen to meet industry standards and requirements. The composition of backup materials was chosen based on compression strength testing. The material selected has high ultimate compression strength and high thermal conductivity and can be readily incorporated in the mold-making process.