Research - Tungsten Reduction

Gaurav Nilakantan

Research—

Undergraduate work II

Most industries which are involved in machining processes use tungsten carbide tools for their cutting operations. One such industry is the Rock-Drilling Industry which encompasses oil rigging, quarrying, mining and water bore well drilling. The working condition in these situations is very harsh, unpredictable and of a very large scale compared to the machine tool processes involving metals.

The drill used should be capable of withstanding the high impact shock involved without failure. Thus it requires a high degree of toughness in its core so that failure doesn’t occur very quickly. From pre-existing knowledge we know that at the microstructure level a higher grain size in a domain helps in increasing the toughness. In steel this is achieved by heat treatment methods, whereas in tungsten this is not possible as its melting point is very high and the grain size can thus only be controlled at the reduction stage of the oxide to the powder itself. This is because later on, there is little noticeable variation in the grain size after the part is sintered, which occurs towards the end of the Powder Metallurgy Process. The parameter measured here is the magnetic saturation (Hc) the tungsten undergoes when subjected to a field which is a direct indication of its toughness and other relevant parameters. This value gives a fair idea about the achievable toughness of the final component.

This project aims at analyzing the hydrogen reduction process employed to obtain Tungsten Powder from its oxide and also analyzing the process parameters responsible for the grain size control, with a final view of obtaining a grain size above 8 microns.

The requirements of Kennametal Widia India Ltd. with regard to coarse grain powder were met by imports from places such as China, which proved far more expensive compared to in-house manufacturing. Since the requirements of the powder grow every year, efforts were on to master the reduction process so as to achieve in-house manufacturing capability which would prove highly economical for the company.