ELECTROLYTE-PLASMA POLISHING OF TITANIUM AND NIOBIUM ALLOYS

Abstract

Titanium and niobium alloys are widely used at present in aircraft, nuclear energy, microwave technology, space and ultrasonic technology, as well as in manufacture of medical products. In most cases production technology of such products involves an implementation of a quality polishing surface. Mechanical and electrochemical methods are conventionally used for polishing products made of titanium and niobium alloys. Disadvantages of mechanical methods are low productivity, susceptibility to introduction of foreign particles, difficulties in processing complex geometric shapes. These materials are hard-to-machine for electrochemical technologies and processes of their polishing require the use of toxic electrolytes. Traditionally, electrochemical polishing of titanium and niobium alloys is carried out in acid electrolytes consisting of toxic hydrofluoric (20–25 %), sulfuric nitric and perchloric acids. The disadvantage of such solutions is their high aggressiveness and harmful effects for production personnel and environment. This paper proposes to use fundamentally new developed modes of electrolytic-plasma treatment for electrolyte-plasma polishing and cleaning products of titanium and niobium alloys while using simple electrolyte composition based on an aqueous ammonium fluoride solution providing a significant increase in surface quality that ensures high reflectivity. Due to the use of aqueous electrolyte the technology has a high ecological safety in comparison with traditional electrochemical polishing. The paper presents results of the study pertaining to the effect of titanium and niobium electrolytic-plasma polishing characteristics using the developed mode for productivity, processing efficiency, surface quality, and structure and properties of the surface to be treated. Based on the obtained results, processes of electrolytic-plasma polishing of a number of products made of titanium alloys BT6 (Grade 5), used in medicine and aircraft construction, have been worked out in the paper.