The 36-year-old surrendered just three points on serve in the opening set and took control of the second with a crosscourt backhand victor that broke Chardy when tied at 4-4.
Federer clinched the victory on his second match point when he blasted his 12th and final ace of the contest.
This was the second official match between Federer and Chung, who had met in the Australian Open in January, where the South Korean retired due to foot blisters when Federer was leading 6-1, 5-2.
After becoming the oldest World Number 1 in ATP rankings in February, Federer claimed that his sights are on winning 100 career titles. "There will always be up and coming players", Federer said after his win over Chung, as quoted by the Express.
According to Christopher Clarey of the New York Times, the 20-time major champion was 15-0 in 2018 entering play Thursday, and 13 of those wins came in straight sets. Cuevas then broke Chung again to close to 5-3, but the Korean closed out the win. But Federer, too, has made a mockery of the calendar and continues to redefine the possibilities for 30-something players.
"I didn't start very well". She could move to 15th or 16th, and has a shot at the top 10 if she would win the title. "I was a little bit frustrated about the game today because the wind didn't give us the rhythm", Halep said in an on-court interview. The Romanian tied it 5-all before Martic won the final two points to force a third set. His forehand volley went wide, giving Chung a break chance. "It is a totally different year, and so many years after that", he said yesterday.
In other men's fourth round action, Croatia's Borna Coric blasted nine aces as he outlasted American Taylor Fritz 6-2 6-7 (6/8) 6-4. Federer has shown that age is just a number since his comeback from a long-term injury at the start of the 2017 season. Del Potro will face Kohlschreiber in the quarterfinals. Qualifier Marcos Baghdatis of Cyprus withdrew from his match against No. 32 Milos Raonic because of illness.
"It's the best I played so far", Querrey said.