Harden Aluminium?

Question

Hi,

I need to harden some aluminium gears for my sons RC car, as they are cheap and keep wearing through.

Unfortunately there aluminium, so I can't flame harden them. Any ideas what process I can use to harden them?

Cheers!

Sorry, forgot to say that I need to harden existing gears. I can't manufacture new ones and just adding grease won't work as the gears are literally bending the teeth, not wearing them away.

If i could buy ones made out of better stuff I would!

Answer 1

Depending on the alloy composition, you have two options. Both methods may be used on some alloys; with the specific composition you could find a more specific answer.

Some aluminum alloys can be hardened by holding them at a temperature high enough to create a homogeneous solution, and quenching them followed by natural or artificial age hardening. Some alloys will age harden at room temperature in several days, others must be held at an elevated but relatively low temperature for anywhere from several hours to a couple days. This process causes the solute to precipitate out of the aluminum grains, resulting in hardening.

Aluminum alloys may also be cold worked or strain hardened, which would require you to deform the metal. Depending on the precision required of the gears, you may be able to slightly deform and then reshape the gears. This process increases the number of dislocations in the crystal structure and decreases the grain size, which hardens the metal.

Answer 2

As someone mentioned the strongest (= hardest) aluminium alloys are the 6 series engineering alloys. After heat-treatment the maximum strength of these alloys is still barely that of annealed low carbon steel. Aluminium is simply unsuited for the purpose to which it is being put.

Even if you diffusion harden the surface the bulk strength will be hardly affected and it will still deform.

Work hardening the piece after shaping is a non-starter. Even if you could repeatedly plastically deform it and return it to its required shape another definition of such cyclical deformation is 'fatigue stress', you'll strengthen the crystals but weaken the crystal boundaries, leading to early failure.

You need to find an alternative material that is either sufficiently hard in the cast state or can be work-hardened to a disc shape out of which the required part is machined or can be heat-treated to the required hardness. Titanium, as suggested, is one possibility, but would be horrendously expensive I suspect for 'special parts'. Another possibility is phosphor-bronze. Obviously it's heavier but it will do the job. Is there any reason why tool steel cannot be used? This is machined to the required shape in the soft state then hardened and tempered by heat-treatment. The volume changes significantly on hardening, however and this needs to be taken into account in the sizing of the pieces.

When it comes to engineering you have two choices, something that is easy and cheap to make that doesn't work or something that is more difficult and expensive but does the job!

Answer 3

This Site Might Help You.

RE:
Harden Aluminium?
Hi,

I need to harden some aluminium gears for my sons RC car, as they are cheap and keep wearing through.

Unfortunately there aluminium, so I can't flame harden them. Any ideas what process I can use to harden them?

Cheers!

Answer 4

Hardening Aluminum

Answer 5

what about cooking them in the oven for a few day or longer
if the flame is to hot for hardening I would think this is a sloe process and the oven is like a low powered kilm so for gears made out of that stuf sounds about right to me but the tempature is a toss up and how many days? I do not know
but I think it will work

Answer 6

Have them electroplated
Electroless Nickle is your best bet,It can be hardend to a similar level to hard chrome,by overnight heating
It is a comformable coating so wont build up on the tips of the teeth
get a new set,send them to us,and we`ll turn them round in a week or so

Answer 7

The hardest alum is 6 series, and I don't think there are treatment to harden it.

Answer 8

If they're cheap, buy some more expensive ones in a different material such as Titanium.

Answer 9

How big are these gears? If it is possible to diffuse another metal then magnesium works well but copper is easier to source although it tends to weaken the corrosion resistance.

Answer 10

it deponds on chemical composition of alumnium . analyse it then ask from a metallurgist.