For any 3D printed parts, a difference in % elongation between the raster direction and transverse direction is expected. Also, I don't know a lot about the HIP process, but it seems like it is intended to densify the printed material by reducing the voids that arrise from the printing process. There shouldn't be any cracks to close in an as-printed part unless the printing process went very badly. In a material like Inconel, the voids probably increase the apparent ductility of the material, therefore when you densify using HIP you should expect a decrease in apparent ductility. In summary, all of your results seem perfectly reasonable to me. You might measure the density of the as-printed part, the post-HIP part, and compare to neat Inconel to help assure yourself.

Look at the microstructures. I suspect formation of delta Ni3Nb and / or Laves phase along the grain boundaries.

I agree, wiht both previous comments. More over, what parametres , esp. temperature, did you use? What was cooling rate?

Usually , the HIP temperature is the same as solution treatment temperature. That means solution of gama prime or double prime. I do not know, what is the recrystalisation temperature of IN718.

If the cooling rate from HIP is slow, usually is, than reprecipitation occurs. Therefore usually Heat treatment sequence follows the HIP.