How is quality factor affected when combining inductors?
The value of Q relates the impedance of the inductor to its resistance:

Q = X(L)/R, so for a frequency f,

Q = 2 pi f L / R.

For a series connection both L and R sum, so

Q' = 2 pi f (2L) / 2R

The factors of 2 cancel, and the Q of the composite inductor (Q') is identical to the Q of the component inductors (for the case identical Qs).

The same calculation can be made for any number of inductors, in series or in parallel. In all cases, the composite Q will lie somewhere between the highest and lowest Qs of the individual components.