Some time ago Microsoft added the encryption option on the disk pane (Azure IaaS properties). Now you don’t need to use the CLI or Powershell commando’s to decrypt/encrypt your VM disks.
Just go to the encryption button and the options already speak for themselves. When you already have one disk encrypted and just added an extra disk you can easily use the (keyvault) settings that are already in place. You can also choose to add an additional keyvault/Key/Version.
Using this command it’s also very easy to disable disk encryption. Just go to Disks to encrypt and choose None. The encryption will be removed.
Make sure that your VM must be up and running (and when you encrypt your OS disk your VM might reboot)