Effect of milling conditions and binder phase content on liquid phase sintering of heat treatable WC-Ni-Co-Cr-Al-Ti cemented carbides

• Published in: International journal of refractory metals & hard materials Vol. 88; p. 105202
• Main Authors: Soria Biurrun, Tomas, Lopez Ezquerra, Belen, Lozada Cabezas, Lorena, Sánchez Moreno, Jose M.
• Format: Journal Article
• Language: English
• Published: Shrewsbury Elsevier Ltd 01.04.2020; Elsevier BV
• Subjects: Age hardening; Aging (artificial); Air cooling; Alloying effects; Aluminum compounds; Aluminum oxide; Cemented carbides; Chromium carbide; Densification; Grain growth; Intermetallic compounds; Liquid phase sintering; Liquid phases; Morphology; Nickel base alloys; Oxidation; Precipitates; Precipitation hardening; Sintering; Solution heat treatment; Superalloys; Titanium; Tungsten carbide; Vacuum sintering
• ISSN: 0263-4368; 2213-3917
• DOI: 10.1016/j.ijrmhm.2020.105202

The binder phase of WC based cemented carbides has been alloyed by adding two different aluminium compounds, AlN and TiAl3, to mixtures comprised of WC, Ni, Co and Cr3C2 powders. A more efficient alloying effect is obtained by TiAl3 additions likely due to its higher dissolution rate during liquid phase sintering. Shrinkage and melting phenomena are strongly affected by the energy of the milling process and the amount of metallic additions. The use of higher milling rotation speed induces higher oxidation of the powder mixtures and the subsequent formation of a higher volume fraction of alumina particles after sintering. Densification and WC grain growth are hindered by increasing the Al addition. Thus, full densification of alloys with higher Al additions require the use of HIP after standard vacuum sintering cycles. As-HIPed WC-Ni-Co-Cr-Al-Ti samples present a binder phase with precipitation of gamma prime similar to that found in as-cast Ni superalloys. The size, volume fraction and morphology of these precipitates has been modified by applying a standard solution treatment (1150 °C-2 h) followed by fast air cooling and subsequent aging at 600 °C and different dwelling times. Age hardening effects have been confirmed in the composition consisting of WC-12 wt% Co-12 wt% Ni-1.7 wt% Cr3C2-5 wt% TiAl3 after 100 h at this temperature. •Heat treatable WC hardmetals have been obtained by liquid phase sintering of WC-Ni-Co-Cr3C2-TiAl3 powder mixtures•Densification and WC grain growth are hindered by increasing the Al addition. HIP is needed to remove residual pores•A higher volume fraction of Al-rich oxides is obtained by increasing the milling rotation speed•As-HIPed WC-Ni-Co-Cr-Al-Ti samples present a binder phase with precipitation of gamma prime.•As in as-cast Ni superalloys, the size, volume fraction and morphology of these precipitates can be modified by aging