You said you had disk corruption. Do you know which file was corrupted?

Also, were you running in archivelog mode?

If you were not running in archivelog mode, I don't think there is anything you can do if you have no backup.

Given archivelog mode.

If it was not the system, there is some hope.
If it wasn't the system tablespace/datafile the following sequence might work.

Crash the database (shutdown abort and/or power down the server without doing a shutdown.)

do a startup mount of the database.
vary the datafile that was corrupted offline
alter the database open.

You might have to do a 'startup nomount'. It depends on your release, platform, config settings, which datafile was corrupted and what cheek your tongue is in.