Gas and Liquid fuel HVOF thermal spray torches have been commercially available for the past 20 years. These torches have different fundamental operating characteristics, such as gas flows, exit gas velocities, and thermal efficiencies. This paper will examine the fundamental operating and design characteristics of the Diamond Jet, WokaJet, JP5000, and WokaStar HVOF torches. Results for total heat input to the torch, thermal efficiency, and design conditions are presented.

Plasma spray torches for spraying internal diameters have typically been limited to 40 kW in the past. A new internal plasma spray torch has been developed with an operational power limit above 90 kW. This high power torch was primarily developed to decrease the spray time required to apply coatings to large inside diameters such as land based gas turbine components. This paper explores the factors effecting the operation of this torch as well as the functional limits of its operation. The factors investigated are gas flow, gas ratios, current, voltage, water flow, and water temperature. Thermal efficiency and plasma enthalpy are presented.

Several attempts have been made in the past to compare the coating costs associated with different processes. These have been based normally on various process related assumptions. The comparisons have typically been biased by the views and objectives of the presenters. A realistic comparison of the process costs needs to be based on the actual production methods and the historical data. This paper presents the comparisons of the Vacuum Plasma process with two versions of the HVOF process. Both small and large part geometries are considered as well as part complexity. The cost data will be presented as an actual cost per part to coat, including both operating costs and amortized capital costs. This method is preferred over the theoretical calculation of the cost per pound of material sprayed. The latter method requires a number of assumptions and does not consider the limitations of production cycles and material handling.