1) 17-4 PH stainless steel is a martensitic stainless steel that is precipitation hardened through heat treatment to improve its yield strength. 2) It contains around 3-5% copper which precipitates out as small particles during aging, strengthening the steel. 3) The precipitation hardening process involves solution heat treatment to dissolve precipitates, quenching to form martensite, and aging to form precipitates that strengthen the martensitic microstructure.

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