Kyp is correct about the Clamp ring on all ANH FX sabers being plastic.
I might point out another source of the creaking blade. It really isn't the blade at all. It is the bladeholder shifting inside the main hilt tube, and at the flex points of the plastic bezels on the Red button and glass eye sections.
I would NOT recommend using WD-40 on the plastic parts of your saber for many reasons.
1. WD-40 is a pertoleum based lubricant, and anti-seize compound, it also contains ether. It can and WILL degrade the plastic parts of your saber, and can cause discoloartion in the polycabronate blade. This can lead to breakdown and weakening of the plastic, and even breakage. The Clear polyc will cloud and yellow, and possibly bubble.
2. Petroleum products are flammable. While there is not a huge amount of electricity flowing through the saber, there still is enough to cause a spark. Leading to damage or injury from fire. Some may scoff at this but it is still a possibility.
3. If enough wd-40 gets to the wiring, it can have adverse effects on the insulating plastic. Therefore breaking it down, and possibly causing a short, and damaging the electronics or the molex connectors. See above for fire hazards.
4. WD-40 is not exactly something you want coming into contact with your skin for prolonged periods. It can cause skin irritation.
5. You will NEVER get the smell of WD-40 out of that saber...
6. WD-40 has been known to strip plated plastic parts VERY quickly.
For things like that, I would recommend a silicone based lubricant that is safe for plastics, wax, or even graphite. These will not degrade the plastics as quickly or readily as WD-40.
Synthetic bearing oil (the clear stuff in the needle applicator tubes) or synthetic sewing machine oil is a good product to look into for this.