EFFECT OF VACUUM HEAT TREATMENT ON OXIDATION BEHAVIOR OF SPUTTERED NiCrAlY COATING

A bond coat for thermal barrier coating (TBC), NiCrAlY coating, is subjected to vac-uum heat treatment in order to remove internal stress before ceramic top coat is de-posited. The effect of vacuum heat treatment on the oxidation behavior of the sputtered NiCrAlY coating has been investigated. The as-sputtered NiCrAlY coating consists of γ-Ni and b-NiAl phases. After vacuum heat treatment, the sputtered NiCrAlY coating mainly consists of γ'-Ni3Al, β-NiAl, γ-Ni, and trace of α-Al2O3 phases. The isothermal oxidation of sputtered NiCrAlY coating with and without vacuum heat treatment has been performed at 1000℃. It is shown that a-Al2O3 formed during vacuum heat treatment acts as nuclei for the formation of a-Al2O3, and the protective a-Al2O3 scale is formed more rapidly on the vacuum heat treated NiCrAlY coating than that formed on the untreated coating. Also the a-Al2O3 scale has a better adherence to the vacuum heat treated NiCrAlY coating. Therefore the vacuum heat treatment improves the oxidation resistance of sputtered NiCrAlY coating.

Phenomenological study on the decay widths of Υ(nS)→d~*(2380)+X

The decay widths of Υ（nS）→d^＊（2380）＋X with n=1,2,3 are studied in a phenomenological way. With the help of crossing symmetry, the decay widths are obtained by investigating the imaginary part of the forward scattering amplitudes between d^＊ and Υ（nS）. The wave functions of d^＊ and deuteron obtained in previous studies are used for calculating the amplitude. The interaction between d^＊（d） and Υ is governed by the quark-meson interaction, where the coupling constant is determined by fitting the observed widths of Υ（nS）→d＋X. The numerical results show that the decay widths of Υ（nS）→d^＊＋X are about 2-10 times smaller than that of d＋X. The calculated momentum of d^＊ is in the range 0.3-0.8 GeV. Therefore, it is very likely that one can find d^＊（2380） in these semi-inclusive decay processes.