PRM1 pilot reported failure of AHRS system after takeoff. The pilot returned to departure airport and landed uneventfully.

Narrative

Started up the plane to fly to ZZZ1 from ZZZ. I was unaware that Maintenance had just changed the AHRS number 1 box out in the aircraft with a new one from Rockwell Collins. I am new to the aircraft as well. AHRS lined up well before taxi however during taxi the number one attitude indicator pitched down and to the right. The number 2 AHRS also appeared to be pointed strangely further down than normal. This was accompanied with roll and pitch flags on the PFD (Primary Flight Display). I have seen AHRS misaligned before on aircraft which can usually be remedied by resetting avionics and letting it realign which I opted to do while holding short of the runway. I coordinated this pause with tower while it realigned. All looked well this time and no more flags. We were cleared for takeoff. At about 300 feet the number one AHRS started to point down and right with the attitude indicator. I look over at number 2 which is also pointing slightly down. Flying on the standby attitude gyro I got above the clouds where I then Experienced a full AHRS 1 failure. Number 2 still worked but it appeared it was giving me bad information. Using nav info on the number 2 PFD and the standby attitude gauge as well as cross referencing heading with wet compass (which still seemed to work) I flew an ILS back and landed. Moving forward I think we will implement a program between lead pilot; the other pilot and maintenance crew to better advise of changes made since the last flight and for me personally I will make a better risk assessment especially for weather like that (low clouds; fog and low vis) and adhere to that more religiously; especially when instruments act up and are questionable like today and until I become more experienced in the aircraft.