We have been asked to weld 17-4PH Stainless Steel, what TIG filler wire would you recommend?

Martensitic precipitation hardening 17-4PH stainless engineering steel possesses very good weld ability and can be treated like a 304 grade for welding procedure. Generally, the most widely used filler wire is 309L or 309LMo. 312 filler metal is also suitable for most work. Other weld alloys include 625 & FM 82.

The 309L types are probably the favourite for ease of procurement and versatile performance. This helps to cope with dilution and maintain a crack-free joint. The L grade is preferred (lower carbon), and the Mo-containing grade gives a bit more pitting corrosion resistance and an even smoother arc action for the welder.

Since the base metal 17-4 PH alloy is low carbon, I recommend the L versions to minimise any grain boundary Chrome-carbide formation during in-service.

Welding Tips & Techniques

No preheat beyond usual ambient shop temperature required, stringer beads with a convex geometry and filled craters. Keep a close arc to preserve CR content. Plus, clean conditions are very important.

For super critical applications in very corrosive and high stress conditions it may be necessary to use a closely matching welding filler wire such as AMS 5825 (as is the case with some military applications).

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