Sandvik Ab

Torbjorn Hartzell

Udo K Fischer

Kauko Karki

Mats G Waldenstrom

Rock drill bit and cutting inserts

There is now provided a cemented carbide button for rock drilling comprising a core and a surface zone surrounding the core whereby both the surface zone and the core contains WC (.alpha.-phase) and a binder phase based on at least one of cobalt, nickel or iron and that the core in addition contains .eta.-phase. In addition, in the inner part of the surface zone situated close to the core, the cobalt content is higher than the nominal content of cobalt and the cobalt content in the outermost part of the surface zone is lower than the nominal and increases in the direction towards the core, up to a maximum usually at the .eta.-phase core. The grain size distribution of the hard constituent in the zone with high cobalt content and in the .eta.-phase core is narrow in contrast to a button of the prior art in which the grain size distribution of the hard constituent in the zone with high cobalt content and the .eta.-phase core is wide. As a result, a button with improved resistance against plastic deformation is obtained. The improvement is obtained by pressing and sintering a powder mixture which has not been milled in the conventional way, but in which the binder phase has been uniformly distributed by coating the hard constituent particles with binder phase.

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Stockholm, Sweden

Torbjorn Hartzell