Direct Carburization of Tungsten Trioxide by Mechanical Alloying

Abstract

Tungsten carbide is the choice of predilection for producing parts requiring good wear resistance. In this context it is produced in large quantities by the carburization of tungsten trioxide under a stream of hydrogen at elevated temperature followed by grinding to achieve the required fineness. This work aims to study the conditions in which tungsten carbide can be produced by mechanical alloying method. Using this method would facilitate obtaining carbide through a simple and easy to use technology without prohibitive costs, directly by an end user. For this purpose the thermodynamic study is conducted to establish the conditions under which the carburizing reaction can take place. The condition for the reaction to occur spontaneously is reaching a temperature of 621°C. Carrying out this reaction in a system without external energy input seems impossible. Mechanical alloying experiments were carried out in a Fritch Pulverisette 7 premium line planetary mill, equipped with two bowls of 80ml capacity lined with sintered tungsten carbide. Each bowl contained 200 g of tungsten carbide balls with dimensions of 10 mm and 12 mm. The balls/load ratio was 10:1. Grinding was performed in steps of 3 hours, with breaks for sampling, with rotation speeds of 600 and 800 rpm. Tests conducted showed complete conversion of raw materials into tungsten carbide after different durations of time.