Polishing Zircalloy

I cannot find any detailed info on polishing of zirconium alloys which makes me believe you should just treat it as any other alloy of aluminium or titanium.

Start with the coarse compound on a stitched mop if the surface defects are very grainy and rough. If this is not the case, you can skip this stage and go straight to the medium or fine compound, depending on the finish of the product before you start.

Normally the medium compounds can be done with either the stitched mop or the loose soft mop but generally if you need a severely fine finish, you stay with the stitched mop for the medium grain and then do the last treatment with the fine compound on the loose mop.

If you do use the same kind of mop for different stages, do not mix the compounds as it may take too much time for it to dilute and you will not get an even result. In this case you best have a separate mop for each stage.

Hi all,

Polishing of zirconium alloys are made in the same form as titanium alloys.

Usually SiC belts or cloths are effective.

It is common to polish in two or more steps, using a coarser grit initially, such as 60 or 80, to remove gross surface roughness, followed by polishing with 120 or 150 grit to provide a smooth finish. Depending on the finishing requirements, further grits (240, 400, etc) can be used.

Zirconium tend to wear the sharp edges of the abrasive particles and to load the belts more rapidly than steel. Frequent belt changes are required for effective cutting. A good flow of coolant improves polishing and extends the life of the abrasives. Common coolant is an aqueous solution of 5% of K₃PO₄

Dry polishing can be applied too for some applications. For these operations, belts or cloth wheels with silicon carbide abrasive may be used. Abrasive belt materials that incorporate solid stearate lubricants offer improved results for dry polishing operations.

Important note: Accumulation of zirconium fines can be pyrophoric.

Depending on the fabrication/production method of the parts and their initial surface condition, electro-polishing may be the answer to provide the final bright finish desired.

Hi,

I agree partially with Stan. I forget to mention electropolishing, but the method selected depends upon the initial roughness resulting from the last manufacturing operations and the required final roughness (and appearance).

Electropolishing requires a previous relative good finishing (unless the last machining were electrochemical, in which case, there will be no question because the result will be equal to electropolishing) and can reach final roughness about 0,05μm (rms or Rq according to ISO designation). It is not a common polishing method used in zirconium alloys.

One problem is the power consumption: To get a fine result you will need current densities in the order of 50 A/cm² minimum.

So our colleague has two options:

• Abrasive polishing
• Non abrasive polishing (ECP)

Another aspect to take into account are cost. We don't speak about it!

The original poster did say that they were finely detailed parts therefor belt abrasion is out of the question as you cannot get into the little nooks and crannies.

Mop polishing first and if required maybe an electro plating treatment afterwards.

Check out www.frost.co.uk for small quantities such as hobby or restoration work.