A model for deposition of metal vapors from multiple targets on a cylindrical substrate

The paper addresses a challenging problem of developing technology for heat exchanger tubes embedded in ceramic composite matrix. Functionally graded composite tubes, made using physical vapor deposition (PVD) process, are required to have diffusion barrier layers, withstand high temperature, and be impermeable to hydrogen. The work addresses mathematical modeling of the deposition of metallic vapors from multiple targets on a cylindrical substrate to simulate the PVD process in manufacturing such tubes. Materials used for the deposition are Molybdenum and Niobium because they have shown good formability, strength, toughness and ductility over a wide range of temperatures. Commercially available software FLUENT was used to model the process. Prediction of condensation of vapors from metal ingots occurs in varying proportion along the circumference of the tube, resulting in submicron layers of different materials of varying thicknesses being ingrained into each other. Results are presented for patterns of materials showing continuously changing relative concentration of deposited metals over a stationary and rotating cylindrical substrate.