Ram unleashed three aces in his 7-6 (7-3), 6-3 decision over the Argentinean.
He goes on to face fellow American and No. 2 seed Sam Querrey, who advanced when his third-round opponent, Belgian Xavier Malisse, retired while trailing 6-2, 3-1 in the second set.
Also notching an upset Friday was Lithuanian qualifier Ricardas Berankis, who dispatched fourth-seeded Nicolas Mahut of France 6-4, 6-4 in a 90-minute match. His semifinal opponent will be Marinko Matosevic of Austria, who downed American Michael Russell 6-2, 6-3.