The keyways on the bronze cones do get worn but an engineer can easily mill out a new keyway to make them as good as new. The chain is prone to jumping on the gypsy as it is only touching two links at a time and this wears the gypsy making the problem worse. Replace the gypsy if this problem becomes serious.The cones, gypsy and shaft keyways get damaged/worn by a jumping chain if the cones are not kept greased because without it the cones can suddenly grab the gypsy when the chain does a runaway and puts huge loads on the whole thing. I know because I have done it and was lucky to find a great engineer in Croatia who repaired the damage.
I had my 80mtr chain regalvanised in Spain for about 180 Euros. After one season it is still as good as new, The process is called hot dipping. The chain is tied to a hoist with wire so that it is in short lenths about 3 or 4 metres long and then dipped into boiling liquid with zinc electrodes in the cauldron and comes out looking like new except that there is a bit of zinc build up at the bottom end of each link from gravity during the suspension treatment.Not important.

Best wishes, Anne and John, Bali Hai, SM 319