Recycling of tungsten carbide scrap metal: A review of recycling methods and future prospects

Abstract

Tungsten’s unique properties and the excellent cutting and wear resistance properties of its carbides have made it a strategic commodity of high importance globally. Cemented carbides, used for the production of tools and components for metal cutting, rock drilling and wear resistance applications, are highly employed in the manufacturing, petrochemical, construction, gas drilling and mining sectors. These materials, with a typical tungsten content of about 40–95 wt%, become available for recycling and re-use when scrapped.Cemented carbide recycling methods are classified into three categories: (1) direct, (2) indirect and (3) semi-direct. The direct methods have advantages of high recoveries, good quality powders’ production and good grain size control. These methods, however, suffer from incomplete separation of metal carbides from the binding material, require specialized costly equipment and are energy intensive. Indirect methods have the advantage of producing ‘virgin Ammonium para tungstate (APT)’, the most important precursor for tungsten intermediate products such as tungsten trioxide, tungsten blue oxide, tungstic acid and ammonium metatungstate. These methods, however, have a shortcoming of long reaction times and use several conversion steps. The semi-direct methods have the advantage of being low on energy requirement and environmental impact. However, these methods have a disadvantage of slow process kinetics.Statistics show that tungsten-based scrap will become an increasingly important source of raw material for the worldwide tungsten industry. Thus the future prospects of recycling will require optimization of current recycling methods, as well as the possible development of new ones with special emphasis on conversion and energy costs, purity of the scrap metal, recovery of all valuable constituents, as well as diminished environmental impact. In this paper, a review of current research efforts and various methods of scrap recovery, future prospects and sustainability of the tungsten industry, are presented.