15-5 stainless steel is a martensitic, precipitation-hardening material with chromium, nickel and copper.  It is often a first choice in the aerospace industry for fasteners and structural components.  Its unique structure provides increased toughness and better corrosion resistance than its predecessor, 17-4 PH.  Both inclusion control and a minimized amount of delta ferrite as compared to 17-4 stainless steel contribute to the greater toughness of 15-5.  The alloy is further strengthened by a low temperature heat treatment which precipitates a copper containing phase in the alloy.  15-5 PH is able to meet the stringent mechanical properties required in the aerospace and nuclear industries.

15-5 PH Chemical Composition

	Element	Percent by Weight
C	Carbon	0.07 maximum
Cr	Chromium	14 – 15.5
Cu	Copper	2.5 – 4.5
Fe	Iron	Balance
Si	Silicon	1.00 maximum
S	Sulfur	0.03 maximum
Ni	Nickel	3.5 – 5.5
Mn	Manganese	1.0 maximum
P	Phosphorus	0.04 maximum
Nb Ta	Niobium plus Tantalum	0.15 – 0.45