You'll find a lot of sintered metal gears these days; Nearly universal in hand power tools for example. They have similar cost advantage as plastic in reduced manufacturing expense compared to machined gears but retain the improved strength and dimensional stability of metal.
In terms of a general statement, its a bit misleading to state that sintered metal gears retain the improved strength of traditional metal gears. They are a lot stronger than plastic gears, but in the majority of cases (particularly in hand power tools), they do not have the strength of traditional machined gears.
As I understand it, the legendary Sturmey Archer bicycle gear hub used sintered internal components, as early as a century ago. Those hubs have extreme longevity. Of course a bike is not a super high power load, but still it's impressive.
