  We study the phase diagram of the t-J model using a mean field type
approximation within the Baym-Kadanoff perturbation expansion for Hubbard
$X$-operators. The line separating the normal state from a d-wave flux or
bond-order state starts near optimal doping at T=0 and rises quickly with
decreasing doping. The transition temperature $T_c$ for d-wave
superconductivity increases monotonically in the overdoped region towards
optimal doping. Near optimaldoping a strong competition between the two d-wave
order parameters sets in leading to a strong suppression of $T_c$ in the
underdoped region. Treating for simplicity the flux phase as commensurate the
superconducting and flux phases coexist in the underdoped region below $T_c$,
whereas a pure flux phase exists above $T_c$ with a pseudo-gap of d-wave
symmetry in the excitation spectrum. We also find that incommensurate
charge-density-wave ground states due to Coulomb interactions do not modify
strongly the above phase diagram near the superconducting phase, at least, as
long as the latter exists at all.
