The Australian was in majestic form throughout as he struck a 103 break to open proceedings and never looked back.
Vafaei was unable to get a foothold at all as Robertson did not score less than 60 points in any frame.
A stunning break of 140 in the fourth frame gave him an emphatic lead and a tally of 101 points in the sixth rounded off a comprehensive thrashing.
'I've lost a bit of respect for him' - Bingham on Selby 'gamesmanship'
'A masterclass' - Robertson hits a dominant 140
Robertson will take some beating on this evidence and he will go into Sunday's final brimming with confidence after not losing a frame in the last-four clash.
'Ruthless' - Robertson wins semi-final with stunning century
Earlier, Stuart Bingham made four centuries on his way to a 6-2 win over world number 103 and fellow Englishman Joe O'Connor in another one-sided semi-final.
23-year-old O'Connor - in his first year on the professional tour - had produced the best performance of his fledging career to reach the last four with victories over green baize heavyweights Kyren Wilson, Ding Junhui and John Higgins.
But the Leicester hopeful struggled against the experience of the 2015 world champion Bingham as he compiled a highest break of only 33 at the Motorpoint Arena in Cardiff.
Bingham toiled with his own game early on, but clicked into gear when it became clear O'Conner was struggling with the conditions.
Breaks of 107, 100, 104, 125 and a closing 67 helped him ease into the 10th major final of his career, and he kindly applauded O'Connor at the end of the match.
He lifted the Welsh Open two years ago, and has already won the English Open this season.
Stuart Bingham 6-2 Joe O'Connor
Neil Robertson 6-0 Hossein Vafaei
- John Higgins 3-5 Joe O'Connor
- Stuart Bingham 5-2 Zhao Xintong
- Hossein Vafaei 5-1 Scott Donaldson
- Neil Robertson 5-4 Kurt Maflin
'Out of order' - Bingham unhappy with Selby 'gamesmanship'
Selby wins marathon semi-final as Bingham fades in fifth session