CVD of Refractory Amorphous Metal Alloys
- PDF / 237,241 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 29 Downloads / 233 Views
M. TENHOVER The Carborundum Company, Technology Division, Niagara Falls, New York 14302-08.32
ABSTRACT In this work, a novel process is described for the fabrication of multi-metallic amorphous metal alloy coatings using a chemical vapor deposition (CVD) technique. Of special interest in this work are amorphous metal alloys containing Mo and/or Cr which have high crystallization temperatures and readily available low decomposition temperature metal-bearing precursors. The conditions for amorphous alloy formation via CVD are described as well as the chemical properties of these materials. High temperature, aqueous corrosion tests have shown these materials (especially those containing Cr) are among the most corrosion resistant metal alloys known.
INTRODUCTION Since the first reports of the formation of amorphous metals, considerable effort has been Made to develop new and commercially viable methods of fabricating useful forms of these interesting materials I l1. Amorphous metals are commonly produced by rapid quenching of liquid alloys (,splat quenching), vacuum evaporation, sputtering, ion-implantation, electrochemical deposition, and surface melting via lasers or e-beams. Recently, new alloys chemistries have allowed the fabrication of bulk amorphous alloys by conventional casting methodsl2l. In all these formation techniques, there are limited alloy chemistries that will form amorphous alloys. Some, such as sputtering can produce amorphous alloys from a wide range of alloy chemistries while others such as liquid quenching are very limited in the compositions that can be quenched into the amorphous structure. In this work, a chemical vapor decomposition/deposition process is described for producing amorphous metal alloys. This method can produce very thermally and chemically stable amorphous materials. Like the other methods mentioned above, there is a limited number of compositions that can be made amorphous with a CVD process. The advantages of using CVD to fabricate amorphous metal alloys is the very high rate of production and the useful form of the material (such as a coating on an object or a free standing monolithic shape).
EXPERIMENTAL PROCEDURES The samples reported in this study were made in the system schematically illustrated below in figure 1. Three types of metallic alloys were investigated: 1. Cr-Mo-N, 2. Cr-Mo-N doped with Pt, and 3. Cr-Fe-Mo. The starting metal sources were chromium hexacarbonyl, iron pentacarbonyl, molybdenum hexacarbonyl, and platinum acetylacetonate. These precursors were chosen because they have decomposition temperatures significantly below that of the expected crystallization temperatures of the targeted amorphous alloy compositions. The powders of these materials were first mixed in the desired ratio and transported by screw-feeder into a feed chamber held between 70 and 100 0 C. The vapors were carried by an Ar stream into the deposition chamber. In addition, nitrogen gas was metered into the chamber as the N source for some of the alloys. The pressure in the depositio
Data Loading...
