Mariah Carey -- BLASTS 'AMERICAN IDOL' ... It Was Like Working In Hell!!!

Mariah Carey says she HATED being a judge on "American Idol" -- claiming everyday it was like "working in hell with Satan."

Carey never mentioned Nicki Minaj by name during the explosive interview with Hot 97 in NYC yesterday ... but it's clear who she was talking about since their feud was no secret.

Carey -- who made $18 mil for her 1st season on the show -- says she was duped by producers who told her she was going to sit on a 3-person panel ... and when they added Minaj as a 4th judge, things quickly spiraled out of control.

"It was like hell ... going to work every day in hell with Satan," Carey said.

We broke the story ... Minaj and Carey fought right from the start -- and in their most famous spat, the rapper told producers, "I'm not f**kin' putting up with her f**kin' highness over there."

So, guess no Christmas duet??