Repartitioning fails in Internet recovery: is the HD salvageable?

Internal HD failure in Early 2011 unibody. Had recent-enough backups (of individual important files, not Time-Machine-formatted), so decided to just reinstall from Internet Recovery. The HD showed in Disk Utility, but showed as a single unformatted partition. Okay, reformat the drive. This gave the "Unable to write to last block" error

On a few subsequent tries, it seems that the internal hard drive will show (unformatted) if I enter Disk Utility immediately, but will not show if I quit and re-enter Disk Utility (without a backup), nor will it show in the Reinstall utility. DU shows no problems recognizing the external HD or optical drive, so it's unique to that drive.

So: is the drive totally borked? I can try to set up the external to boot from, but I imagine it would throw a similar error. I opened up the case and checked that the HD cable and bracket weren't loose or dusty, but I didn't look for anything more specific than that.