Nice cage... looked a good 1k with the work material labour and head scratchingAye but not often do thieves carry a 9" grinder with them.
Hardfacing, well should i say most widely available hardfacing, doesn't really slow down an abrasive disc.
I have some products here which make it much much more difficult to grind through, far too expensive for most though. spherical carbide in touch nickel matrix is one.
With the above being 40mm thick i was just looking to slow them down or at least run the batteries out on their grinder before they could get through.

It had to be bored out so I did it from the bore to the outside. Piling rig socket end