Sintering of metallic diamond alloy powders

Abstract

Metallic diamond (MD) is a new alloy class which hardness was found to surpass any current alloys at more than a twofold factor, up to 2500 HV (kgf mm−2). The alloy design employs simple metallurgical principles at the so-called Lattice Occupancy Project aided by Diamoy 1.0 software. The most important aspect of the alloy project considers the maximization of chromium equivalent values by selecting metallic elements for promoting body-centred cubic structures. Forming these alloys into parts is challenging, whereas powder metallurgy techniques appear as valid processing routes. The work studies the sintering behaviour of MD-4 and 5 alloy powders, being the hardest MD ones. High energy milled powder compacts were sintered in a dilatometer up to 1500 °C for 1 h under Ar-10%H2 atmosphere. Alloy MD-5 has shown intense shrinkage starting at 1150 °C, contrasting to marginal sintering of alloy MD-4. The latter has undergone transformations from 400 °C with strong expansion, which seems to block most of the sintering retraction at higher temperatures. Alloy powder MD-5 is a good candidate as a raw material for tool parts production by powder metallurgy, which can compete with cemented carbide hard tools.