Cyber-conversion

Cyber-conversion was the physical and mental re-engineering of Human victims into Cybermen. In an alternate universe, this was referred to as Upgrading.

Cybermen
Cyber-conversion involved the replacement of body parts (including limbs, organs, and vital systems) with artificial components. (DW: Attack of the Cybermen) Partial conversion, with the victim retaining autonomy and a human identity and body parts, was possible. (DW: The Invasion)

The Cybermen would traverse the universe to find beings to convert, adding to their forces. (DW: Attack of the Cybermen) The Cybermen relied on tubing to keep the body operating, but over time the amount needed decreased. (DW: The Tenth Planet onwards)

Cybermen of Pete's World
The Cybermen of Pete's World, instead of replacing body parts, transplanted living brains into metal exoskeletons sustained in a cradle of chemicals and threaded together by an artificial nervous system. The process was extremely painful and took place in a booth where the subject was surgically mutilated by a robotic machine that used knives, lasers and syringes to remove the brain before encasing it in an empty cybernetic helmet. This was the most efficient way of conversion. They also had an Emotional inhibitor placed within them to suppress their humanity because, as the Tenth Doctor put it;


 * It's still got a human brain... imagine its reaction if it could see itself. Realise itself inside this thing. They'd go insane....

During the Battle of Canary Wharf, the Cybermen, badly needing reinforcements, quickly converted Humans into Cybermen using a different method instead of just transplanting brains. They encased Humans in cybernetic shells by constructing the suit of armour around their body, as with Lisa Hallett. Hallett would have died if her lover, Ianto Jones, had not managed to retrofit a cyber-conversion unit into life support for her. (TW: Cyberwoman)


 * It may be that the reason why certain converts with exceptionally strong willpower like Yvonne Hartman could overcome their programming was because this form of conversion was less precise and more rushed.

The Cybermen also employed a very primitive type of conversion in 1851 when they created the cybershades using scrap metal and Victorian technology. They also invented a way of converting humans into command units for Cyber Kings by fitting them with a headset that could take control of their brains.

A Cyberman's exo-skeleton from DW: The Pandorica Opens displayed the ability to upgrade Humans without any external machinery, merely needing to restrain the victim while the Cyberman's faceplate splits open at the middle and envelopes the victim's head. The process from here on is unknown, as the only seen victim of this process is Amy Pond, who escaped before the process was completed. This Cyberman seemed to have a similar upgade like that during the Battle of Canary Wharf, due to the fact that the Canary Wharf upgrade involved consealing the body inside the suit, while this Cyberman had a severed head concealed in its helmet.

Cybermen

 * Toberman- Partial cyber-conversion on Telos, regained his humanity and attacked the Cyber-Controller. Sacrificed his life to close doors of the Cybermen's tombs (DW: The Tomb of the Cybermen)
 * Bates and Stratton - Cyber-conversion process failed at an early stage after their limbs had been replaced by mechanical equivalents. Put to work on the surface of Telos with similar such failures. (DW: Attack of the Cybermen)
 * Lytton - Partial cyber-conversion on Telos, cyber-conversion incomplete at the time of his death (DW: Attack of the Cybermen)
 * Bill and David were converted. (DW: Attack of the Cybermen)
 * Evelyn Smythe (alternative timeline) - (WC / BFA: Real Time)
 * Tobias Vaughn - Partial cyber-conversion, retained head and therefore his own thoughts. (DW: The Invasion)

Cybermen of Pete's World

 * John Lumic - Converted into Cyber-Controller
 * Sally Phelan
 * Jackie Tyler of an alternative universe - Alternate counterpart of Jackie Tyler
 * Yvonne Hartman - Torchwood Institute administrator
 * Lisa Hallett - Torchwood employee and lover of Ianto Jones, partial cyber-conversion (TW: Cyberwoman)
 * Mercy Hartigan - CyberKing. Miss Hartigan refused to be converted to a standard Cyberman and took control of the Cybermen which landed in 1851. The Cybermen, however, had slowly set a plan in motion that would eventually make Miss Hartigan both a convert and a leader. (DW: The Next Doctor)

Cybermen of unknown origin

 * Elizabeth Meadows underwent partial conversion. She tricked the Doctor into releasing the Cybermen from stasis by pretending to be her former human self. (VG: Blood of the Cybermen)