High Velocity Oxy-Fuel Flame Spraying-Process and Coating Characteristics

Abstract

High velocity oxy-fuel (HVOF) spray experiments were carried out using various spray systems. A comparison is made of the systems introduced as a first and second generation (Jet Kote, Diamond Jet, Top Gun, CDS) with the more recently introduced systems of the third generation (JP 5000, DJ 2600, DJ 2700). The comparison is based on particle velocities and experiments to evaluate the heat transfer to the particles. The results show that the systems of the new generation with a converging-diverging nozzle section can produce up to 50% higher particle velocities. The higher kinetic energy allows to reduce the thermal energy and to reduce thermally activated phase transformations of the coating material during the spray process. Carbide coatings produced with one of the new HVOF systems exhibit a higher density, higher bond strength and higher hardness as compared to coatings produced with one of the systems of the first and second HVOF generation. Furthermore, the reduced thermal energy yields less oxidative loss of carbon and opens the possibility to spray coatings with neutral or compressive internal stresses, a prerequisite to produce carbide coatings up to a thickness of several millimeters.

Properties of WC‐CoCr Based Coatings Deposited by Different HVOF Thermal Spray Processes

“…Moreover, systems which employ a gaseous fuel such as hydrogen yield comparatively higher particle temperatures and lower velocities than systems which employ a liquid-fuel such as kerosene. [8,12] As a consequence, a higher temperature combined with a lower velocity increases the residence times of the particles in the hot gas. If the temperature of any region of a heated particle exceeds the melting temperature of the WC-CoCr pseudoternary eutectic, dissolution of the WC in the liquid CoCr occurs.…”

Investigation of the Influence of Powder Fraction on Tribological and Corrosion Characteristics of 86WC-10Co-4Cr Coating Obtained by HVOF Method

“…However, the number of studies on the influence of initial powder fractions on the properties of coatings obtained by HVOF method is poorly understood. Most authors in their works mainly considered the influence of powder particle size distribution (including WC) on the microstructure, wear resistance and corrosion properties of thermally sprayed WC-Co-Cr coatings [34][35][36][37][38].…”