sgdisk -R /dev/sdY /dev/sdX
Randomize GUID:
sgdisk -G /dev/sdY
View details of raid device:
mdadm --detail /dev/mdY
Remove device if nesessary:
mdadm /dev/md4 -r /dev/sdY4
Add the device again:
mdadm /dev/md4 -a /dev/sdY4
Install Grub on the new disk:
grub-install /dev/sdY