Can vibratory tumbler be used for work hardening?

   1. Can vibratory tumbler be used for work hardening? I
understand that vibratory are faster than the rotary ones, are there
any other advantages? 

Vibratory and rotary tumblers will both cause work hardening AT THE
SURFACE of the metal, when used with steel shot media. Vibratory
tumblers don’t seem to burnish/harden the metal to as deep into the
surface, perhaps because the individual shot are not moving as far
and don’t seem to have quite the speed and inertia that they can
develop in a rotary tumbler, especially the larger size barrels with
larger size shot. So in this use, the rotaries harden more. I like
them better, in general, for steel shot, unless you’re talking about
the especially powerful vibratory types, like the Gyrocs, for example.
However, in general, when using media OTHER than steel shot, such as
the various ceramic or plastic grinding/polishing media, or walnut
shell or the like, then the vibratory tumbers are a LOT faster than
rotaries.

2. I live in Sigapore now, where electric current is 220V, but I
plan to come back to the US in a couple of years. Is it possible to
use tumbler and ultrasonic cleaner made for 110V with 220V (with a
transformer/adaptor perhaps)? I don't want to burn expensive
equipment! 

If your equipment is rated 110 volts, that that is what it has to be
fed. But if you use a step down transformer, you can easily convert
220 to 110. So long as the frequency is also the same as the
equipment wants, you’ll be fine. Most U.S. equipment wants’ 50-60 HZ,
and at least so far as I know, most 220 lines are also one of those
two. If the frequency does not match, you can still convert, but it
is likely to be a considerably more costly converter, as it
essentially has to convert to DC current, and then back to the
desired AC frequency/voltage. one other note, when converting from
220 volts to 110 volts, as the voltage is cut in half, the amperage
output doubles. So to feed a piece of equipment thats rated at, say,
8 amps of 110 current, your converter will only need to draw a bit
over (the “bit over” is because there is a slight loss, due to heating
of the transformer) 4 amps of 220 current from the wall to deliver
that 8 amps. But be sure that your converter IS capable of
delivering sufficient output amps, as well as the needed voltage, to
run your equipment.

HTH
Peter Rowe