The influence of nozzle design on HVOF exit gas velocity and coating microstructure

Abstract

A simple device was constructed for determining a value for the average combustion gas velocity at the exit plane of a high-velocity oxyfuel gun. This device was used to measure the velocities of a standard factory-made barrel nozzle and a specially designed de Laval nozzle as a function of the fuel/oxygen ratio and the total mass flow rate. The Mach number of the de Laval nozzle was 1.42. The maximum combustion gas exit velocities determined for the standard and the de Laval nozzles were 1100 and 1550 m/s, respectively. The maximum velocity depends on the fuel/oxygen ratio but is independent of the total flow rate. The effect of increased combustion gas velocity on coating quality is demonstrated.

Yb2Si2O7 Environmental Barrier Coatings Deposited by Various Thermal Spray Techniques: A Preliminary Comparative Study

“…A MultiCoat system (Oerlikon Metco, Wohlen, Switzerland) with three-cathode TriplexPro 210 and Diamond Jet 2700 spray torches mounted on a six-axis robot (IRB 2400, ABB, Switzerland) was employed for APS and HVOF spray experiments, respectively. The HVOF burner was fitted with a convergent-cylindrical design nozzle (Type 2705) which yields lower particle velocities and thus longer dwell times in comparison to that of convergent-divergent nozzles [26]. A VLPPS investigation was performed with an O3CP torch operated by the MultiCoat platform (Oerlikon Metco, Wohlen, Switzerland) in a controlled-atmosphere chamber.…”

Review: The Impact of Metal Additive Manufacturing on the Aerospace Industry

“…This process involves the jetting of metallic particles through an expanded supersonic gas flow, providing the particles with sufficient kinetic energy to impart plastic deformation and bonding to an impacted surface ( Figure 12) [125]. As the metal particles are pushed through a Laval nozzle the flow temperature drops as the particles are accelerated by up to 1200 m/s [126], resulting in metal droplets being deposited on the targeted area to cover the damaged region. Thus, the SPD technique is viewed as a viable and effective repair solution for damaged components, in addition to DED repairs.…”

Application of High-Velocity Oxygen-Fuel (HVOF) Spraying to the Fabrication of Yb-Silicate Environmental Barrier Coatings

“…The HVOF burner was fitted with a convergent cylindrical design nozzle (Type 2705) which yields lower particle velocities and thus longer dwell times in comparison to that of a convergent-divergent nozzle [18]. Methane has been used as the fuel gas in the HVOF process.…”