Hmm I shouldn't run with memory too far... Ti6-4 data sheet says 1600-1650 so we'll meet in the middle

ASM Material Data Sheet

I'm sure your burner is oxidised just can't see it. Like Stainless and aluminium the oxides are nearly transparent. You can heat it and get the blues and yellows, golds like the stainless steel welding rings. Some motorbike exhausts in Ti are heated to a specific temp to turn them bright blue. Cheers Peter