RF induction plasma spraying: State-of-the-art review

Abstract

Radio frequency (RF) induction plasma technology has gained wide acceptance for the preparation of plasma spray coatings and structural free-standing parts of metals, ceramics, and metal-matrix composites. Its principal advantages are the relatively large volume and low velocity of the discharge, which coupled with the ease of axial injection of the powder into the plasma allows for the melting of relatively large particles at high throughput. The absence of electrodes offers the added advantage of ease of operation under a wide range of conditions at atmospheric and low pressure, with an inert, reducing, or oxidizing atmosphere. Highlights of recent advances in induction plasma melting and deposition of materials are presented in this article. The first section deals with advances in induction plasma spraying technology including system and torch design. This is followed by a brief overview of mathematical modeling and diagnostic studies of the induction plasma deposition process. Examples of applications of induction plasma spraying for the preparation of protective coatings and fiber-reinforced metal matrix composites are presented in the final section.