The document discusses several coating processes including plasma spray, which uses a plasma jet over 20,000 K to melt and propel particles onto a substrate, complete melting is important for uniformity and residual stress can occur from uneven thermal expansion. It also discusses high velocity oxygen fuel coating which uses supersonic particle velocities over 1000 m/s for bonding through kinetic energy without melting, and produces a noisy diamond shock cell structure, and chemical vapor deposition such as low pressure CVD for integrated circuits where temperature control is critical and surface chemistry depends on temperature and gas concentration.

1. Plasma Spray Process
• Plasma jet can reach very high
temperature > 20,000 K
• Plasma disassociation effect
(ionization) is important to
enhance heat transfer
• Almost applicable to any
materials: ceramics, metal,
plastics, etc.
• Splat pattern of a single
particle
• Complete melting of the
particle is critical for
uniform coating
• Residual stress due to
uneven thermal expansion
is important

2. Residual Thermal Stress

3. High Velocity Oxygen Fuel (HOVF)
• Very high velocity (>1000 m/s supersonic range)
• Existence of diamond shock-cell structure; very noisy
• High kinetic energy of the particles is responsible for the
bonding (no melting is required).

4. Chemical Vapor Deposition (CVD)
 Low pressure CVD (LPCVD)
 Integrated circuit
 Temperature control is critical
 Combined mass and heat
transfers
 Surface chemistry is
governed by surface
temperature & gas flow
concentration