Characterization of an Axial-Injection Plasma Spray Torch

The Axial III™ torch is a multiple-arc plasma generator with a set of three single cathode–anode units, which is still of significant importance, especially in the field of suspension plasma spraying. The division of the plasma generator into three spatially separated systems allows for central feedstock injection with improved deposition rates and efficiencies. In this work, several diagnostic methods were applied to characterize the plasma jet of an Axial III™ spray torch to further the understanding of this spray system. One important result was that the plasma temperature in the jet exhibits a triple distribution with three straight lobes arranged around the jet axis. As with every plasma torch, the total plasma power is subject to fast temporal variations. Power variations were clearly seen in the plasma jet even though it could have been anticipated that the triple jet characteristics and the natural fluctuations of the arcs generated by the three single cathode–anode units would be less pronounced after merging the three plasma streams. Unaffected by this it is nevertheless likely that the axially injected feedstock particles are caged effectively in the core of the plasma jet. Hence, the total electrical torch power and the uniformity of the single unit’s powers must be monitored to realize possible degradation and asymmetries in the plasma temperature distribution, which may influence deposition parameters.

Next Generation Axial III Torch

The Axial III, launched in 1994, is a patented plasma spray torch with axial injection of feedstock. In comparison to the traditional radial injection, axial injection technology has proven to offer greater deposition efficiency, throughput, and cost savings on numerous applications [1]. Despite these benefits, the original Axial III M600 torch had several limitations due to its size, mass, and number of components. To address these shortcomings, a smaller, lighter, and more ergonomic version of the torch was developed, called the Axial III Plus, that produces the same high-quality coatings at high feed rates and deposition efficiency. This paper highlights the innovations in this new torch and the potential applications it opens for the plasma spraying industry.

Bioactive and Tribological Behaviour of Atmospheric Plasma Sprayed Hydroxyapatite Coatings Reinforced by Lanthanum Oxide

Lanthanum oxide (La2O3) reinforced Hydroxyapatite coating was deposited by using unique gas tunnel type plasma spray torch under optimum spraying conditions. The phase and microstructure of the as-prepared powder and coatings were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). In vitro bioactivity of the plasma sprayed lanthanum oxide reinforced hydroxyapatite coatings were investigated by using simulated body fluid solution. Results showed that there was onset of apatite formation on the surface of coatings after 15 days of immersion in SBF, while after 19 days of immersion in SBF it was indicated that a HCAp phase crystallized on their surface. Our studies demonstrate that lanthanum oxide reinforced hydroxyapatite coatings are potentially useful biomaterials with good tribological and bioactive behaviour.