1958 Volume 44 Issue 2 Pages 146-150
Carbides electrolytically isolated from low W-Cr cutting-tool steels were studied by X-ray and chemical analysis, and the following results were obtained.
(1) The principal carbide in annealed structure of low W-Cr tool steels was M23C6 (κ-carbide). Cementite containing W amd Cr (θ-carbide) also appeared in the low-W grade steels.
(2) By tempering of these steels, hexagonal ε-carbide precipitated in the first stage, and θ-carbide in the third stage of tempering, amd at last κ-carbide appeared by the tempering above 650°C.
(3) In the fourth stage of tempering, an enrichment of Cr and W into carbides occurred and was increasingly marked with the rise in tempering temperature. The rate of enrichment of W into carbides was exceedingly slow compared with that of Cr.
(4) In an chromium-free W steel, κ-carbide was decomposed by annealing, and by heating to quenching temperature, accompanied by the formation of WC and η-carbide. This tendency was reduced by the alloying of Cr, V and Mo, and was promoted by Ni, Co and Si.