Novel fine-grained hardmetals by use of multiphase powder precursors and reactive nitrogen sintering

作者：Janisch D S; Lengauer W^*; Roediger K; Dreyer K; van den Berg H

来源：International Journal of Refractory Metals and Hard Materials, 2010, 28(3): 362-369.

DOI：10.1016/j.ijrmhm.2009.11.012

• Hardmetal
• Cemented carbide
• Cermet
• Sub-micron
• Gradient
• Nitrogen
• Reactive sintering

Hardmetals typical of ISO class P which contain hexagonal WC together with fcc carbides and carbonitrides as hard phase constituents were prepared ranging from very low to very high carbonitride contents by a novel route. For this purpose specially designed multiphase hard phase powders containing both, WC and pre-alloyed fcc carbides were used. Green bodies were reactively sintered at various nitrogen pressures. During this step, not only carbonitride formation but also WC formation takes place. The sintered hardmetals were characterised by XRD, EBSD, SEM and LOM. They show sub-micron grain size of both, the WC and the fcc hard phase and thus substantially higher hardness (with only a small decrease in toughness) as compared to conventionally prepared bodies of the same overall composition. As a consequence, flank wear of cutting inserts is significantly reduced in milling of 4140 steel. Grain growth is retarded due to the pre-alloyed state of the powders and the interpenetration of hexagonal and fcc hard phases.
The applied method, both, in laboratory and industrial scale, allows not only adjustment of the bulk properties of the hardmetals during sintering but in addition, if desired, tailoring the near-surface microstructure with respect to the formation of various types of a functional gradient.

• 出版日期2010-5