The popular American hit seven aces as he despatched Chardy 6-2 7-6 in 85 minutes.
He will face Fabio Fognini in the quarter-finals after the Italian upset fourth seed Bernard Tomic, coming from a set down to defeat the lanky Australian 4-6 6-3 7-5.
Denis Istomin also produced an upset as he overcame the second-seeded Spaniard Marcel Granollers 6-1 4-6 7-6. He plays Ryan Harrison in the last eight after the American beat Yen-Hsun Lu 6-1 7-6.
Defending champion Andreas Seppi of Italy defeated Carlos Berlocq of Argentina 7-6 6-3, and goes on to play Germany's Philipp Kohlschreiber.
Marcos Baghdatis hit 11 double faults as he suffered a 6-4 4-6 6-4 defeat to Belgium's Steve Darcis, who will now take on Australian qualifier Marinko Matosevic.