PH 13-8 Mo is a stainless steel with approximately 13% chromium and 8% nickel content that has good resistance to corrosion in general as well as to stress corrosion cracking. PH 13-8 Mo offers better mechanical properties in demanding environmental conditions in comparison to other materials based on iron. Precise control of the microstructure is achieved through vacuum melting and remelting. Medium to high strength can be achieved through precipitation hardening aging treatments.

Chemical composition - limits in %

PH 13-8 Mo stainless can be readily forged, hot headed and upset. Material which is hot-worked must be solution treated prior to hardening if the material is to respond properly to hardening.

Heat uniformly to 2150/2200°F and hold 1 hr at temperature before forging. Do not forge below 1750°F. To obtain optimum grain size and mechanical properties, forging should be cooled in air to 60°F before further processing. Forging must be solution treated prior to hardening.

PH 13-8 Mo stainless can be fabricated by cold working to an extent which is limited by the high initial yield strength.

Bars and forging billets should be cold cut by sawing. Abrasive wheel cutting can cause small surface cracks, particularly when cutting annealed stock, and should be avoided.

PH 13-8 Mo stainless can be machined in both the solution treated and various age-hardened conditions. In Condition A the alloy gives good tool life and surface finish when machined at speeds 20 to 30% lower then those used for Custom 630 (17Cr-4Ni) or 20 to 30% lower than used for Stainless Type 302 and 304. The machinability as age-hardened will improve as the hardening temperature is increased.

 

Conditon H 1150M provides optimum machinability. Having procures Conditon H 1150M for best machinability, higher mechanical properties can be developed only by solution treating and heat treating at standard hardening temperatures.

PH 13-8 Mo stainless can be welded using the inert-gas shielded or resistance welding processes. When a filler metal is required, PH 13-8 welding consumables should provide welds with properties similar to those of the base metal. When designing the weld joint, care should be exercised to avoid stress concentrators, such as shrap 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 annealed 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 welding. However, the optimum combination of strength, ductility and corrosion resistance is obtained by solution treating the welded part before aging. If welded in the overage condition, the part must be solution treated before aging.