Stainless Steel Grade 15-5 PH (UNS S15500)

Topics Covered

Chemical Composition
Mechanical properties
Manufacturing process


Stainless steel 15 – 5 PH, also known as XM-12 or UNS S15500, is a modification of 17-4 PH developed in the 1960s. It has a more refined microstructure obtained through the remelting process. This refined structure improves toughness of the material. UNS S15500 also has low temperature hardening, good fabrication properties and excellent corrosion resistance, which makes it suitable for many industries. It can be machined in the solution-annealed state or in final heat treat condition. The strength and ductility of UNS S15500 can be enhanced through heating the material at different temperatures.

UNS S15500 is a martensitic precipitation hardening type stainless steel. Martensitic stainless steels were designed to be corrosion resistant and hardened through heat treatment.

Chemical Composition

The chemical composition of Grade 15-5 PH stainless steel is outlined in the following table.

Element Content (%)
Iron, Fe 75
Chromium, Cr 14.48
Nickel, Ni 4.5
Copper, Cu 3.5
Manganese, Mn ≤1
Silicon, Si ≤1
Nb + Ta 0.3
Carbon, C ≤0.07
Phosphorous, P ≤0.04
Sulfur, S ≤0.03

Mechanical properties

The mechanical properties of Grade 15-5 PH stainless steel are displayed in the following table.

Properties Metric Imperial
Tensile Strength 1380 MPa 200000 psi
Yield Strength 1275 MPa 184900 psi
Modulus of Elasticity 200 GPa 29000 ksi
Elongation at Break 10% 10%
Hardness, Brinell 420 420
Hardness, Knoop 451 451
Hardness, Rockwell B 104 104
Hardness, Rockewell C 44.2 44.2
Hardness, Vickers 445 445
Charpy Impact 10 J 7.38

Manufacturing process

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UNS S15500 can be machined under any of the attainable conditions. Firstly, the alloy is mildly formed in the overaged condition. It is then welded using welding techniques such as shielded fusion or resistance methods. The material is heat treated at 1038°C (1900°F) for 1/2 h, and then air cooled. This process is followed by hot-working the material and annealing at 1038°C (1900°F) for 1 h. Finally, the alloy can be cold-worked to improve its yield strength.


The following are some of the major applications of Grade 15-5 PH stainless steel:

  • Marine gas turbine compressor sections
  • Hallow shafts
  • Paper mill equipment
  • Engine parts
  • Aircraft components
  • Gears
  • Fittings and fasteners
  • Nuclear reactor components

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