Page 51 - PCMI Journal July 2018
P. 51
David Allen | Emeritus Professor | Cranfield University | UK Photochemical Machining of Aerospace Materials
5/31/18
Use of HF-corrosion resistant materials in etching machines
• A standard etching machine comprises structural polymer sheets, such as PVC, and components made from titanium and other polymers.
• If HF is going to be used as a spray etchant, this means all titanium parts need to be replaced by corrosion- resistant polymers or superalloys such as Hastelloy C-276 or given additional protection by means of corrosion- resistant polymer coatings.
• Even Hastelloy C-276 should not be immersed in HF solutions continuously. The etchant should be removed from the machine and then the machine should be washed out thoroughly with water.
Corrosion-resistant Hastelloy-C276
Chemical composition of Hastelloy C-276
Nickel (Ni)
≈55% (balance)
Molybdenum (Mo)
15 - 17%
Chromium (Cr)
14.5 - 16.5%
Iron (Fe)
4 - 7%
Tungsten (W)
3 - 4.5%
Cobalt (Co)
2.5%
Vanadium (V)
0.35%
Silicon, manganese, carbon
traces
Issue 131 July 2018 PCMI Journal 50
7
