In the second set, Zhang broke Buyunchaokete's serve in the seventh game and saved a break point in the eighth game to hold serve, ultimately winning the second set 6-4 before securing the victory, reports Xinhua.
Post-match statistics showed that Buyunchaokete had more break opportunities than Zhang.
"Buyunchaokete played better than me, but some mistakes, such as the double fault in the tiebreaker, gave me a bit of luck in the first set," Zhang said.
The Chinese top-ranked player will face former US Open champion Marin Cilic of Croatia, who entered the tournament with a wildcard and defeated the fourth-seeded Brandon Nakashima of the United States in straight sets in the other semifinal.
"He has a very high-quality baseline game that compensates for his movement, which is something I need to overcome tomorrow," said Zhang, adding that he did not expect to reach the final before coming to Hangzhou and will do his best in the final.