tlavanway3 85C is normal for 1080 Ti reference (founders) cards. 84C is normal for 980 Ti reference cards. The hard is in no danger of becoming damaged, but it will moderately thermal throttle. You could either do a custom fan curve, as iamacow suggested, or return your card for a GPU with a closed loop AIO cooler, such as EVGA 1080 Ti FTW3 hybrid. Since the Nvidia refresh is coming this year, and the hybrid is now selling for slightly over $1,000 (original street price was $850) I'd probably just hold onto your current card and push the fan RPM up a tad.