Two c-TiAl based alloys of Ti-48Al-2Nb-2Cr (at-%) and Ti-45Al-2Nb-2Mn-1B (at-%) were used as substrate materials. The coatings' deposition process was prepared using the slurry method. After the deposition of water based slurry containing Al and Si powders on the substrates, diffusion treatment has been carried out at 1000uC for 6 h in Ar atmosphere. The structure of the silicon modified aluminide coatings is as follows: (a) an outer layer consisting of a TiAl 3 matrix and Ti 7 Al 5 Si 12 grains dispersed within this matrix, (b) a middle layer composed of a TiAl 3 matrix and columnar grains of Ti 5 Si 3 and (c) an inner layer as TiAl 2 phase. According to the energy dispersive spectroscopy analysis results, it can be concluded that Cr had a high tendency to move towards the Si enriched compounds. The results of isothermal oxidation test of 1000uC/200 h showed that the formation of Si modified aluminide coatings on c-TiAl alloys by slurry method can greatly improve their high temperature oxidation resistance.

No abstract

No abstract

Ahigh pressure sensor based on an optical fiber micro sphere cavity Fizeau interferometer (MSC-FI) is presented in this paper.The sensorwas fabricated by use of a fusion splicer. The achieved pressure sensitivity of MSC-FI sensor was in the range of 500 to 7000pi to be 4×10 -4 nm/psi. With a 10 pm resolution for the wavelength shift detection, the resolution of the device at room temperature for pressure measurement is to be 25 psi. This sensor can be used as a high pressure sensor in downhole application.