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1. 17-4 PRECIPITATION
HARDENABLE STAINLESS STEEL

2. INTRODUCTION:
 17-4 PH stainless steel is one of the most common martensitic stainless
steel.
 17-4 PH Stainless steel is precipitation hardening of martensite
stainless steel.
 Precipitation hardening is a special type of heat treatment technique
used to improve the yield strength of the material.
 It is also called age hardening (or) particle hardening.

3. Composition of 17-4 PH Stainless steel:
The composition of 17-4 PH Stainless steel is
Carbon 0.07%
Chromium 15% - 17%
Nickel 3% - 5%
Copper 3% - 5%
Manganese 1%
Columbian+ Tantalum 0.15% - 0.45%

4. • Precipitation hardening stainless steels are characterized into one of
three groups based on their final microstructures after heat treatment.
The three types are:
1. Martensitic (E.G. 17-4 PH),
2. Semi-austenitic (E.G. 17-7 PH)
3. Austenitic (E.G. A-286).

5. Martensite stainless steels:
 It is one of the type of PH stainless steels.
 In this they are already martensitic in solution and annealed condition
and only requires precipitation hardening.
 Martensite stainless steels are similar to iron carbon alloys that are
austenitized .
 They are hardened by quenching and tempered for increased ductility
and toughness.
 Their heat treated structure is BCT (Body centred tetragonal).
 These alloys are magnetic.

8. PRECIPITATION HARDENED HEAT TREATMENT:
 It consists of three stages:
1) Solution Heat treatment
2) Quenching
3) Precipitation or Aging
Solution Heat treatment:
 It consists of high temperature heat treatment that allows any
precipitates and alloying element to dissolve or go in to super saturated
state.
 Temperature is around 980 – 1065C.

9. Quenching (or) Cooling:
 After the alloys are brought to solution the metal is cooled to room
temperature.
 Cooling can be done in air, water or oil but must be accomplished fast
enough to obtain a super saturated solution.
Precipitation (or) Aging:
 The super saturated solid solution decomposes with time or temperature
as the alloying elements forms small clusters.

10. Precipitation Treatment for 17-4 PH:
 17-4 PH stainless steel is a martensitic stainless steel containing
approximately 3% copper and is strengthened by precipitation of
copper in the martensite matrix.
 Addition of copper is made to promote its precipitation hardening
capability.
 Precipitation hardened by only holding the steel at 480C for 1 hour.
 Thereby minimizing scaling and distortion and allowing the parts to be
machined to close tolerances , prior to heat treatment.
 These coherent particles are transformed to incoherent FCC – cu after
long term aging at temperature about 400c.

11. AGING TIME VS YIELD STRENGTH OF 17-4 PH STAINLESS STEEL.

12. Properties:
• High strength
• High Hardness
• Good corrosion resistance.
• Resistance to atmospheric corrosion
• Good machinability
• Resistance to stress corrosion cracking
• Magnetic
• Coherency

13. Limitations:
 Dimensional inaccuracy occurs due to heat treatment and should be
carefull.
 stress cracking occurs.
 Scaling and distortion may occur.

14. Applications:
 Pump shafts
 Pulp and paper industry
 Aerospace ( Turbine blades)
 Food industry
 Off shore (foils, helocopter deck platforms)
 Oil and petroleum refining eqiupment
 Chemical process equipment.
 Gears
 Paper mill equipment
 Air craft parts

16. References:
1. Journal Microstructural Evolution in a 17-4 PH Stainless
Steelafter Aging at 400 &CM. MURAYAMA, Y. KATAYAMA,
and K. HONO
2. http://www.azom.com/article.aspx?ArticleID=2819
3. https://app.aws.org/wj/1998/11/kotecki/
4. Journal PRECIPITATION HARDENING P/M STAINLESS
STEELS by Chris Schade, Pat Stears Hoeganaes Corporation
Cinnaminson, NJ 08077 Alan Lawley, Roger Doherty ,Drexel
University Philadelphia, PA