The present invention provides a deposition process for plasma enhanced chemical vapor deposition of a coating on a substrate. The process comprises detennining a target process condition within a chamber of an expanding thermal plasma generator; the generator comprising a cathode, a replaceable cascade plate and an anode comprising a concentric orifice; and thereafter replacing the cascade plate with another plate having a configured orifice to effect the identified target process condition. The plasma is then generated at the target process condition by providing a plasma gas to the plasma generator and ionizing the plasma gas in an arc between cathode and anode within the generator and expanding the gas as a plasma onto a substrate in a deposition chamber.