Study on the subsonic speed flame spraying coating of hydroxyapatite

A new method of preparation of biomaterial composite coating by the techniqueof subsonic thermal spraying was discussed in this paper. Ti_6Al_4V and pure Ti were chosen assubstrate and sublayer material respectively and the working layer was sprayed with biomaterialhydroxyapatite (HAP), forming the composite coating. The experiments of heat shock and tensilestrength showed that the bonding strength between coating and substrate is almost as same as that ofspecimen in which Ni/Al powder was adopted as sublayer. The phases of TiN, TiO_2, and Ti_2O_3 wereformed in the sublayer, which are free of toxic and have no side effects. The powder of workinglayer HAP was decomposed partly during spraying, but it can be solved by later treatment.

Flame Pyrolysis Spraying of Alumina-Yttria Ceramic Coating

Alumina yttria composite oxide coating was obtained on the stainless steel through the pyrolysis of aluminium nitrate and yttrium nitrate by flame spraying in the open atmospheric environment. The isothermal oxidation behaviour of the specimens coated with alumina yttria was investigated in air at the temperature of 1273 K. The results show that coating can promote the selective oxidation of chromium in the alloy and improve the high temperature corrosion resistance of the stainless steel.

Applying Thermal Spraying to Forming Glass Enamel Coatings

Applying thermal spraying to forming glass enamel coatings is explored in present paper. Four kinds of glass enamel frits suited to flame spraying have been prepared and the flame spraying experiments have conducted. It is possible to form glass enamel coatings on still substrates by a proper flame spraying technique. Besides the obvious mechanical adhesion obtained by roughening the surface of the still substrates, the element micro diffusion between glass enamel coatings and substrates have been produced during the spraying process, Hence metallurgical chemical adhesion is derived.

CORROSION FAILURE ANALYSIS OF FLAME SPRAYED Zn-A115 COATING IN SEA WATER

The morphology,microstructure,chemical composition and electrochemical behavior of the flame sprayed Zn-Al15 coating after corrosion test in sea water have been investigated.The results show that the selective dissolution of the laminar euteetic structure of the Zn-AI15 coating is the fundamental cause for its similarity in electrochemical behavior with Zn coating and kinetic behavior with Al coating.In the beginning period of sea water corrosion,the com- bined action of the laminar eutectic structure of the coating together with the residual stress may induce the stress corrosion cracking of the coating,and result in the crevice corrosion. The coating then will bulge and.fail in local areas due to embrittlement itself,stacking and ex- pansion of corroded products under the residual stress.

The Synthetic and Mechanical Properties of a Silica Matrix Cermet Composite

A cermet composite was prepared by employing thermal spraying flame onto stainless steel surfaces of(304)type.Hence 25,50%of aluminum was mixed with matrix of(10%Al_(2)O_(3)-SiO_(2)).A spray system consistis of oxygen barrel,acetylene and spray gun that contains powders feeder at different spray distances(5,10,15,20 and 25 cm).The thermal treatment of the samples resulting from spraying was performed at 1100℃for 1.5 hr.Some physical examinations(porosity and adhesion),mechanical tests(hardness and wear rate)and Atomic Force Microscope(AFM)test were performed before and after thermal treatment.The test results showed that the best mixing rate was(50%)and the best spray distance was(15cm)where the quality of coating layer improved after thermal treatment at 1100℃for 1.5 hr with a porosity ratio reduced from 11.2%to 6.6%,and adhesion strength improved with the increase in the alumina content to 50%.The results demonstrated that the best adhesion value after thermal treatment was 30.98 MPa.The hardness of coating layer increased from 45.78 to 54.88 HV;while the lowest rate of wear was at 50%of alumina with a spray distance of 15cm.Also,there was a clear improvement based on AFM within grain size,root mean square and roughness rate.

Structural and photocatalytic characteristics of TiO_(2) coatings produced by various thermal spray techniques

Titanium dioxide(TiO_(2))was elaborated by four different thermal spray techniques-(i)plasma spraying using a water-stabilized torch,(ii)plasma spraying using a gas-stabilized torch,(iii)high velocity oxy-fuel gun,and(iv)oxy-acetylene flame.The porosity of the coatings was studied by optical microscopy,nano-structural features by scanning electron microscopy(SEM),phase composition by X-ray diffraction(XRD);the microhardness,surface roughness and wear resistance were evaluated.The diffuse reflectance was measured by ultra-violet/visible/near-infrared(UV/Vis/NIR)scanning spectrophotometer.The kinetics of photocatalytic degradation of gaseous acetone was measured under a UV lamp with 365 nm wavelength.After all the applied spray processes,the transformation of anatase phase from the initial powders to rutile phase in the coatings occurred.In spite of this transformation,all the coatings exhibited certain photocatalytic activity,which correlated well with their band gap energy calculated from reflectivity.All the coatings offer relatively good mechanical properties and can serve as robust photocatalysts.