Walker enjoyed much success throughout the second round, hitting three consecutive birdies over a four-hole stretch to take a one-shot lead at the halfway stage of the tournament.
Walker, who started on the back nine, began his round with two birdies in his first five holes before carding his only bogey of the day when his seven-foot putt slid past the hole on the 17th.
The American rounded off his opening nine with a birdie before going on to record three more birides on the closing nine, which included a lovely 19-foot putt on the seventh hole.
Overnight leader Hoffman faltered on Friday as he hit three bogeys on his second nine to fall to second place on the leaderboard, tied with Aaron Baddeley who recorded a 71.
Jordan Spieth took advantage of the excellent weather conditions to hit five birdies and two bogeys during his second round 69.
Spieth remains two shots behind Walker and shares fourth place with Kevin Na, who hit a 68 following his disappointing first round 72.
Meanwhile, Phil Mickelson is four strokes behind Walker following his second round 72. Joining Mickelson in sixth place on the leaderboard are Brendan Steele, Chris Kirk, Billy Horschel and Zach Johnson.