What heat treat condition is the 17-4PH?
Is it already aged? I hope that it is H1050 or H1100.
If so then I would weld with an austenitic filler.
I would have to look, but perhaps 310, though the safe choice is Ni82.
Carpenter Stainless 17Cr-4Ni can be satisfactorily welded by the shielded fusion and resistance welding processes. Oxyacetylene welding is not recommended, since carbon pickup in the weld may occur. When a filler metal is required, AWS E/ER630 welding consumables should be considered to provide welds with properties matching those of the base metal. When designing the weld joint, care should be exercised to avoid stress concentrators, such as sharp corners, threads, and partial-penetration welds. When high weld strength is not needed, a standard austenitic stainless filler, such as E/ER308L, should be considered.
Normally, welding in the solution-treated condition has been satisfactory; however, where high welding stresses are anticipated, it may be advantageous to weld in the overaged (H 1150) condition. Usually, preheating is not required to prevent cracking.
If welded in the solution-treated condition, the alloy can be directly aged to the desired strength level after welded. However, the optimum combination of strength, ductility and corrosion resistance is obtained by solution treating the welded part before aging. If welded in the overaged condition, the part must be solution treated and then aged.
After welding with E/ER308/309 or Nickel base filler per Ed and metengr, one should consider appropriate tempering to achieve desired hardness/strength properties.
Thank you for the comments. I was leaning toward ER309. The material is solution treated with no PWHT required. It is to be a wear ring in a rotating foundation.
You never use 17-4PH in the annealed condition, it have very poor ductility and truly unknown strength.
Typically for this kind of weld you would have the 17-4 in the H1050 or H1100 condition, weld with 309 or Ni 82, and then post weld stress relieve at a temp that is 25F below the aging temp (i.e. 1025 or 1075).
