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Manufacture of thick chromium coatings by R.F. plasma spraying for PVD sputter targets

Book ·
OSTI ID:379570
;  [1]; ;  [2]
  1. Freiberg Univ. of Mining and Technology (Germany)
  2. Univ. de Sherbrooke, Quebec (Canada)
The production of plasma-sprayed thick chromium coatings on copper substrates for PVD sputter targets contains a number of technological challenges which were tried to be addressed using r.f. plasma spray technology. The efforts were focused on several objectives. The coatings should be as dense as possible. Their residual stresses should be low enough to avoid strong substrate bending and to prevent failure in adhesion or cohesion of the coating. The deposition efficiency during spraying should be as high as possible. Different spraying parameters were varied in order to find the optimum conditions for the spraying process. Two different powder grain sizes were used. First a spheroidization study was performed which gave evidence about the optimum chamber pressure, the optimum plasma power, and a manageable range of the powder feed rate. During spraying of the coatings the power feed was further optimized. Also the spraying distance, the substrate roughness and the substrate cooling were optimized. The substrates were respectively non-cooled, gas-cooled or directly water-cooled. The water-cooled samples showed no substrate bending. However, the thermal stresses were strong enough to cause failure in adhesion or cohesion of the coating. The non-cooled samples showed the best adhesion while the substrate bending could be kept in acceptable limits. Powder feed rates up to about 55 g/min yielded the densest coatings with optimum deposition efficiency.
OSTI ID:
379570
Report Number(s):
CONF-9509182--; ISBN 0-87170-541-9
Country of Publication:
United States
Language:
English