Development and characterization of yttria stabilized zirconia and Al2O3 thin films by pulsed laser deposition:Special Issue

The present study concerns development of yttria stabilized zirconia (YSZ), Al2O3 and a multilayer of Al2O3-YSZ thin film deposition by pulsed laser deposition (PLD) technique for its application as thermal barrier coating (TBC). The detailed study included characterization (microstructure, composition, phase and surface topography) of the thin film. The phase analysis of the YSZ films deposited at room temperature showed amorphous feature, while the film deposited at high temperature showed the formation of tetragonal phase. Residual stress analysis of the coating showed the presence of compressive stress and was maximum at 573 K (sigma(11) = -8.1 GPa and sigma(22) = -6.4 GPa). Residual stress was found to decease with increase in substrate temperature and was found to be lowest at 973 K (sigma(11) = -3.0 GPa and sigma(22) = -1.7 GPa). The cross-sectional morphology of the YSZ and Al2O3 thin films deposited at room temperature showed presence of inter-columnar porosities which changed to a dense structure with increase in substrate temperature

Diode laser assisted surface nitriding of Ti-6Al-4v: properties of the nitrided surface

In the present study, a detailed investigation of mechanical and electrochemical properties of laser-surface-nitrided Ti-6Al-4V has been carried out. Laser treatment is carried out by melting the surface of Ti-6Al-4V substrate using a high power CW diode laser with nitrogen as shrouding environment. The effect of laser parameters (applied power and gas flow rate) on the properties of the nitrided surface was evaluated. The microhardness of the nitrided surface was improved to a maximum of 1175 VHN in the present set of laser processing conditions as compared to 280 VHN of as-received substrate. Surface nitriding increased the potential for pit formation (E pit) significantly as compared to as-received Ti-6Al-4V. Immersion in Hank's solution showed calcium phosphate deposition from the solution. The optimum process parameters for laser surface nitriding were derived