Walking, robotic hydraulics / footsteps

Epic Soundsound effect

Photocopier sounds are good for robotic hydraulics/footsteps.
– Paul Arnold

Close mic a DVD player door closing, it will give you a motorised sound ending with a thud. You can then mix in the sounds of the surface the robot is walking on, e.g. cornstarch for snow etc.
– Ian Brooker

For robotic sounds, these sfx libraries feature a wealth of recordings and designed robot sounds.