Coating vacuum plasma spray

Fig. 10. Scanning electron microscope (SEM) micrograph of the surface of vacuum plasma sprayed hydroxyapatite (HA) coating after treatment in the fluoridating solution (KF 0.05 M KH2PO4 0.15 M pH 7, temperature 100 C). A layer of thin needle-like fluorhydroxyapatite crystals (0.5-3 m long, 0.1-0.3 m width) can be observed. (With kind permission of Springer Science and Business Media).

Figure 5.28 Cross-sectional SEM images of vacuum-plasma sprayed (VPS) coatings type Cl (a) and C2 (b) after immersion in HBSS for 7 days, showing a network of microcracks and debonding along macrocracks parallel to the interface (Vu and Heimann, 1996).

Chang, C., Shi, J., Huang, J., Hu, Z., and Ding, C. (1998) Effects of power level on characteristics of vacuum plasma sprayed hydroxyapatite coating. J. Therm. Spray Technol., 7 (4), 484-488. 

Gledhill, H.C., Turner, I.G., and Doyle, C. (1999) Direct morphological comparison of vacuum plasma sprayed and detonation gun sprayed hydroxyapatite coatings for orthopaedic applications. Biomaterials, 20 (4), 315-322. 

Brossa F, Cigada A, Chiesa R, Paracchini L, Consonni C (1994) Post-deposition treatment effects on hydroxylapatite vacuum plasma spray coatings. Biomaterials 5 855-857 Brown CD, Mealey BL, Nummikoski PV, Bifano SL, Waldrop TC (1998) Hydroxylapatite cement implant for regeneration of periodontal osseous defects in humans. J Periodontol 69 146-157 Brown PW, Fulmer M (1996) The effects of electrolytes on the rates of hydroxylapatite formation at 25 and 388°C. J Biomed Mater Res 31 395-400... 

The accepted method to coat metals is vacuum plasma spraying (VPS), but a new method called high velocity oxy-ffiel (HVOF) thermal spraying has been developed and is more cost-effective and has thus made the use of composites much more practical. 

The mechanical strength of the thin-film cell as well as the electrical and thermal conductivity are provided by an open porous metalfic substrate which also serves as a fuel gas distributor. The functional layers of the cell - anode, electrolyte, and cathode - are consecutively deposited onto this substrate by a multistep vacuum plasma spray process. The contact from the cathode to the ferritic steel interconnect (bipolar plate) is provided by a flexible and ductile perovskite coating. An... 

The anode of the lightweight SOFC is made from Nickel oxide (NiO) and yttria-stabilized zirconia. For the electrolyte, yttria-stabUized zirconia is also used, while the cathode is made from lanthanum strontium manganite (LSM) (cf. previous section). The same material is used for the contact layer. Lanthanum strontium chromite is applied as a ceramic protective coating for chromium retention. The noble gas argon is used as an auxiliary medium in the vacuum plasma spraying process [71]. 

Fig. 1.6. Scanning electron micrographs showing the microstructures of plasma-spray coating of NiCrAlY on a 1020 steel substrate, (a) Air plasma spray coated layer with inter-splat cracks whose origin can be traced to the oxidation of A1 in the coated material during deposition. (6) Vacuum plasma sprayed coating of the same material without inter-splat microcracks. Reproduced with permission from Alcala et al. (2001).)...

For applications requiring higher density coatings with a strong adhesion to the substrate, low-pressure plasma spray is employed where spraying is done in an inert-gas container operating at a reduced pressure. Vacuum plasma spray is another thermal spray process which is used to improve purity of the deposited material and to reduce porosity and defect content, albeit at a higher cost than air plasma spray. 

Yang, Y.C. (2007) Influence of residual stress on bonding strength of the plasma-sprayed hydroxyapatite coating after the vacuum heat treatment. Surf. Coat. Int., 201, 7187-7193. 

S. Sharafat, A. Kobayashi, Y. Chen, and N. M. Ghoniema, Plasma spraying of micro-composite thermal barrier coatings, Vacuum, 65, 415-425 (2002). 

A. Afrasiabi, A. Kobayashi, Hot corrosion control in plasma sprayed YSZ coating by alumina layer with evaluation of microstmcture and nanoindentation data. Vacuum 88 (2013) 103—110. 

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