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The Russian – who also made the final four at last year's US Open – was in control of the quarter-final when Korda retired hurt with a wrist problem at Melbourne Park on Tuesday.
Khachanov led 7-6 (7-5) 6-3 3-0 when the American called it a day, and will face either Stefanos Tsitsipas or Jiri Lehecka next.
The number 18 seed had to work hard to take the opening set, with Korda initially saving himself when Khachanov served for it at 5-3, but the latter eventually came through on a tie-break.
Some ferocious and accurate hitting from the baseline was proving to be decisive for Khachanov, hitting 12 winners in each of the first and second sets.
Halfway through the second set, 29th seed Korda received a medical timeout for a right wrist issue that was clearly impacting his forehand, and from there he won just one more game before retiring.
"For sure, back-to-back semi-finals in a grand slam feels great," Khachanov said in his on-court interview after the match.
"Obviously not the way you want to finish the match. I think until a certain point it was very competitive, a very good battle. Sebastian beat one of my friends, Daniil [Medvedev], in three sets and won in five sets against [Hubert] Hurkacz. He is playing great tennis."
Data Slam: Khachanov serves up a treat
Although clearly aided by Korda's struggles later in the contest, Khachanov was impressive on his serve throughout, only being broken once when serving for the first set.
He was able to win 80 per cent (40 of 50) of points on his first serve.
Khachanov – 12/0
Korda – 4/2
Khachanov – 27/18
Korda – 18/39
BREAK POINTS WON
Khachanov – 4/10
Korda – 1/3