KasperCalc: MIL-HDBK-5 2.6 Precipitation and Transformation Hardening Steel

Chapter 2.6 Contents

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Chapter 1 Chapter 2 Index 2.1 — General 2.2 — Carbon Steels 2.3 — Low-Alloy Steels 2.4 — Intermediate Alloy Steels 2.5 — High Alloy Steels 2.6 — PH & Transformation Hardening 2.7 — Austenitic Stainless Steels Chapter 3

Disclaimer

For reference use only. The formulas, graphs, and values herein are provided in good faith for general engineering guidance. Please verify all data against MIL-HDBK-5J or the applicable superseding document (MMPDS).

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2.6Precipitation and Transformation Hardening Steel (Stainless)

2.6.0Comments on Precipitation and Transformation Hardening Steels

The precipitation and transformation hardening steels in this section include both austenitic and martensitic stainless steels that are hardened by precipitation or transformation mechanisms. These steels combine corrosion resistance with high strength and are widely used in aerospace structural applications.

2.6.0.1Metallurgical Considerations

The precipitation hardening stainless steels achieve their high strength through precipitation of intermetallic compounds during aging treatments. The martensitic grades (e.g., 17-4PH, 15-5PH, Custom 450, Custom 455, Custom 465, PH13-8Mo) are supplied in the annealed or solution-treated condition and strengthened by a single aging treatment. The semi-austenitic grades (e.g., AM-350, AM-355, PH15-7Mo, 17-7PH) require a conditioning treatment to transform the austenite to martensite before aging.

The high chromium content (typically 12 -“18%) provides corrosion resistance. The nickel content stabilizes the austenite in the semi-austenitic grades, while molybdenum, copper, aluminum, and titanium additions are used to provide precipitation hardening response.

2.6.0.2Manufacturing Considerations

Heat Treatment: Heat treating procedures for these steels are specified in MIL-H-6875. The designations used in the property tables (e.g., H900, H950, H1000, H1025, H1050, H1100, H1150 for the martensitic grades; TH1050, RH950, SCT 850 for the semi-austenitic grades) refer to specific heat treatment conditions defined in that document. The number in the designation generally corresponds to the aging temperature in degrees Fahrenheit.

Machining and Forming: The martensitic PH grades are best machined and formed in the annealed or solution-treated condition prior to the final aging treatment. The semi-austenitic grades in the austenitic condition have forming characteristics similar to austenitic stainless steels.

2.6.0.3Environmental Considerations

The precipitation hardening stainless steels are susceptible to stress corrosion cracking (SCC) particularly at the higher strength levels (lower aging temperatures). The martensitic grades heat treated to H900 condition are most susceptible. As the aging temperature is increased (H950, H1000, etc.), SCC resistance improves at the expense of strength. Protective coatings and design practices to minimize sustained tensile stresses in corrosive environments are recommended for the higher-strength conditions.

2.6.1AM-350

AM-350 is a semi-austenitic precipitation hardening stainless steel with nominally 16.5% chromium, 4.5% nickel, and 2.75% molybdenum. It is available in sheet, strip, plate, bar, and forging forms.

2.6.1.0Material Specifications and Design Properties

Table 2.6.1.0(a) -” Material Specifications for AM-350
Table 2.6.1.0(b) -” Design Mechanical and Physical Properties for AM-350
Table 2.6.1.0(c) -” Additional Design Properties for AM-350

Figure 2.6.1.0

Effect of temperature on the physical properties of AM-350 stainless steel.

2.6.1.1SCT 850 Condition

Figure 2.6.1.1.1

Effect of temperature on F_tu and F_ty for AM-350 (SCT 850).

Figure 2.6.1.1.2

Effect of temperature on F_cy for AM-350 (SCT 850).

Figure 2.6.1.1.3

Effect of temperature on F_su for AM-350 (SCT 850).

Figure 2.6.1.1.4

Effect of temperature on F_bru for AM-350 (SCT 850).

Figure 2.6.1.1.6(a)

Typical stress-strain and tangent-modulus curves for AM-350 (SCT 850), longitudinal.

Figure 2.6.1.1.6(b)

Typical stress-strain and tangent-modulus curves for AM-350 (SCT 850), transverse.

2.6.2AM-355

AM-355 is a semi-austenitic precipitation hardening stainless steel with nominally 15.5% chromium, 4.5% nickel, 2.75% molybdenum, and 0.13% carbon. It is available in sheet, strip, plate, bar, and forging forms.

2.6.2.0Material Specifications and Design Properties

Table 2.6.2.0(a) -” Material Specifications for AM-355
Table 2.6.2.0(b) -” Design Mechanical and Physical Properties for AM-355
Table 2.6.2.0(c) -” Additional Design Properties for AM-355
Table 2.6.2.0(d) -” Design Properties for AM-355 (alternate condition)
Table 2.6.2.0(e) -” Additional Design Properties for AM-355 (alternate condition)

Figure 2.6.2.0

Effect of temperature on the physical properties of AM-355 stainless steel.

2.6.2.1SCT Condition

Figure 2.6.2.1.1

Effect of temperature on F_tu and F_ty for AM-355 (SCT).

Figure 2.6.2.1.2

Effect of temperature on F_cy for AM-355 (SCT).

Figure 2.6.2.1.3

Effect of temperature on F_su for AM-355 (SCT).

Figure 2.6.2.1.4

Effect of temperature on F_bru for AM-355 (SCT).

2.6.3Custom 450

Custom 450 is a martensitic precipitation hardening stainless steel with nominally 15.5% chromium, 6.0% nickel, 0.75% molybdenum, and 1.5% copper. It is solution treated and aged to achieve the desired strength level.

2.6.3.0Material Specifications and Design Properties

Table 2.6.3.0(a) -” Material Specifications for Custom 450
Table 2.6.3.0(b) -” Design Mechanical and Physical Properties for Custom 450 (H900)
Table 2.6.3.0(c) -” Design Mechanical and Physical Properties for Custom 450 (H1050)

Figure 2.6.3.0

Effect of temperature on the physical properties of Custom 450 stainless steel.

2.6.3.1H900 Condition

Figure 2.6.3.1.1

Effect of temperature on F_tu and F_ty for Custom 450 (H900).

Figure 2.6.3.1.2

Effect of temperature on F_cy for Custom 450 (H900).

Figure 2.6.3.1.5

Effect of temperature on E, E_c, and G for Custom 450 (H900).

Figure 2.6.3.1.6

Typical stress-strain and tangent-modulus curves for Custom 450 (H900).

Figure 2.6.3.1.8

Typical S/N curves for Custom 450 (H900).

2.6.3.2H1050 Condition

Figure 2.6.3.2.1

Effect of temperature on F_tu and F_ty for Custom 450 (H1050).

Figure 2.6.3.2.2

Effect of temperature on F_cy for Custom 450 (H1050).

Figure 2.6.3.2.5

Effect of temperature on E, E_c, and G for Custom 450 (H1050).

Figure 2.6.3.2.6

Typical stress-strain and tangent-modulus curves for Custom 450 (H1050).

Figure 2.6.3.2.8

Typical S/N curves for Custom 450 (H1050).

2.6.4Custom 455

Custom 455 is a martensitic precipitation hardening stainless steel with nominally 11.75% chromium, 8.5% nickel, 2.25% titanium, and 0.5% molybdenum. It is capable of being aged to very high strength levels.

2.6.4.0Material Specifications and Design Properties

Table 2.6.4.0(a) -” Material Specifications for Custom 455
Table 2.6.4.0(b) -” Design Mechanical and Physical Properties for Custom 455

Figure 2.6.4.0

Effect of temperature on the physical properties of Custom 455 stainless steel.

2.6.4.1H950 Condition

Figure 2.6.4.1.1

Effect of temperature on F_tu and F_ty for Custom 455 (H950).

Figure 2.6.4.1.2

Effect of temperature on F_cy for Custom 455 (H950).

Figure 2.6.4.1.5

Effect of temperature on E, E_c, and G for Custom 455 (H950).

Figure 2.6.4.1.6

Typical stress-strain and tangent-modulus curves for Custom 455 (H950).

Figure 2.6.4.1.8(a)

Typical S/N curves for Custom 455 (H950), unnotched.

Figure 2.6.4.1.8(b)

Typical S/N curves for Custom 455 (H950), notched.

2.6.4.2H1000 Condition

Figure 2.6.4.2.1

Effect of temperature on F_tu and F_ty for Custom 455 (H1000).

Figure 2.6.4.2.2

Effect of temperature on F_cy for Custom 455 (H1000).

Figure 2.6.4.2.5

Effect of temperature on E, E_c, and G for Custom 455 (H1000).

Figure 2.6.4.2.6

Typical stress-strain and tangent-modulus curves for Custom 455 (H1000).

Figure 2.6.4.2.8

Typical S/N curves for Custom 455 (H1000).

2.6.5Custom 465

Custom 465 is a martensitic precipitation hardening stainless steel with nominally 11.75% chromium, 11.0% nickel, 1.75% titanium, and 1.0% molybdenum. It offers higher strength than Custom 455 with improved SCC resistance.

2.6.5.0Material Specifications and Design Properties

Table 2.6.5.0(a) -” Material Specifications for Custom 465
Table 2.6.5.0(b) -” Design Mechanical and Physical Properties for Custom 465 (H950)
Table 2.6.5.0(c) -” Design Mechanical and Physical Properties for Custom 465 (H1000)
Table 2.6.5.0(d) -” Additional Design Properties for Custom 465

Figure 2.6.5.0(a)

Effect of temperature on the physical properties of Custom 465 stainless steel.

2.6.5.1H950 and H1000 Conditions

Figure 2.6.5.1(a)

Effect of temperature on F_tu and F_ty for Custom 465 (H950 and H1000).

Figure 2.6.5.1(b)

Typical stress-strain and tangent-modulus curves for Custom 465 (H950).

Figure 2.6.5.1(c)

Typical stress-strain and tangent-modulus curves for Custom 465 (H1000).

2.6.6PH13-8Mo

PH13-8Mo is a martensitic precipitation hardening stainless steel with nominally 12.7% chromium, 8.2% nickel, 2.2% molybdenum, and 1.1% aluminum. It offers excellent transverse toughness and uniformity of properties due to vacuum arc remelting.

2.6.6.0Material Specifications and Design Properties

Table 2.6.6.0(a) -” Material Specifications for PH13-8Mo
Table 2.6.6.0(b) -” Design Mechanical and Physical Properties for PH13-8Mo (H950)
Table 2.6.6.0(c) -” Design Mechanical and Physical Properties for PH13-8Mo (H1000)

Figure 2.6.6.0

Effect of temperature on the physical properties of PH13-8Mo stainless steel.

2.6.6.1H950 and H1000 Conditions

Figure 2.6.6.1.1

Effect of temperature on F_tu and F_ty for PH13-8Mo (H950 and H1000).

Figure 2.6.6.1.6(a)

Typical stress-strain and tangent-modulus curves for PH13-8Mo (H950), longitudinal.

Figure 2.6.6.1.6(b)

Typical stress-strain and tangent-modulus curves for PH13-8Mo (H950), transverse.

Figure 2.6.6.1.6(c)

Typical stress-strain and tangent-modulus curves for PH13-8Mo (H1000).

Figure 2.6.6.1.8(a)

Typical S/N curves for PH13-8Mo (H950), unnotched.

Figure 2.6.6.1.8(b)

Typical S/N curves for PH13-8Mo (H950), notched.

Figure 2.6.6.1.8(c)

Typical S/N curves for PH13-8Mo (H1000).

2.6.715-5PH

15-5PH is a martensitic precipitation hardening stainless steel with nominally 15.2% chromium, 5.0% nickel, 3.5% copper, and 0.3% niobium/columbium. It was developed to provide better transverse toughness than 17-4PH through vacuum induction melting.

2.6.7.0Material Specifications and Design Properties

Table 2.6.7.0(a) -” Material Specifications for 15-5PH
Table 2.6.7.0(b) -” Design Mechanical and Physical Properties for 15-5PH (H900)
Table 2.6.7.0(c) -” Design Mechanical and Physical Properties for 15-5PH (H1025)
Table 2.6.7.0(d) -” Design Mechanical and Physical Properties for 15-5PH (H1150)

Figure 2.6.7.0

Effect of temperature on the physical properties of 15-5PH stainless steel.

2.6.7.1General Design Properties

Figure 2.6.7.1.1

Effect of temperature on F_tu and F_ty for 15-5PH (multiple conditions).

Figure 2.6.7.1.4

Effect of temperature on F_bru for 15-5PH.

Figure 2.6.7.1.6(a)

Typical stress-strain and tangent-modulus curves for 15-5PH (H900).

Figure 2.6.7.1.6(b)

Typical stress-strain and tangent-modulus curves for 15-5PH (H1025).

Figure 2.6.7.1.6(c)

Typical stress-strain and tangent-modulus curves for 15-5PH (H1150).

2.6.7.2H1025 Condition

Figure 2.6.7.2.2

Effect of temperature on F_cy for 15-5PH (H1025).

Figure 2.6.7.2.6(a)

Typical stress-strain and tangent-modulus curves for 15-5PH (H1025), longitudinal.

Figure 2.6.7.2.6(b)

Typical stress-strain and tangent-modulus curves for 15-5PH (H1025), transverse.

Figure 2.6.7.2.8(a)

Typical S/N curves for 15-5PH (H1025), unnotched.

Figure 2.6.7.2.8(b)

Typical S/N curves for 15-5PH (H1025), notched.

Figure 2.6.7.2.8(c)

Typical S/N curves for 15-5PH (H1025), additional data.

2.6.7.3H1150 Condition

Figure 2.6.7.3.2

Effect of temperature on F_cy for 15-5PH (H1150).

Figure 2.6.7.3.6

Typical stress-strain and tangent-modulus curves for 15-5PH (H1150).

2.6.8PH15-7Mo

PH15-7Mo is a semi-austenitic precipitation hardening stainless steel with nominally 15.2% chromium, 7.1% nickel, 2.2% molybdenum, and 1.2% aluminum. In the TH1050 condition, austenite is conditioned at 1400-°F, refrigerated to −100-°F to transform to martensite, then aged at 1050-°F.

2.6.8.0Material Specifications and Design Properties

Table 2.6.8.0(a) -” Material Specifications for PH15-7Mo
Table 2.6.8.0(b) -” Design Mechanical and Physical Properties for PH15-7Mo (TH1050)
Table 2.6.8.0(c) -” Additional Design Properties for PH15-7Mo

Figure 2.6.8.0

Effect of temperature on the physical properties of PH15-7Mo stainless steel.

2.6.8.1TH1050 Condition

Figure 2.6.8.1.1

Effect of temperature on F_tu and F_ty for PH15-7Mo (TH1050).

Figure 2.6.8.1.4

Effect of temperature on F_bru for PH15-7Mo (TH1050).

Figure 2.6.8.1.6(a)

Typical stress-strain and tangent-modulus curves for PH15-7Mo (TH1050), longitudinal.

Figure 2.6.8.1.6(b)

Typical stress-strain and tangent-modulus curves for PH15-7Mo (TH1050), transverse.

Figure 2.6.8.1.6(c)

Typical stress-strain and tangent-modulus curves for PH15-7Mo (TH1050), short-transverse.

Figure 2.6.8.1.8(a)

Typical S/N curves for PH15-7Mo (TH1050), unnotched sheet.

Figure 2.6.8.1.8(b)

Typical S/N curves for PH15-7Mo (TH1050), notched sheet.

Figure 2.6.8.1.8(c)

Typical S/N curves for PH15-7Mo (TH1050), bar.

Figure 2.6.8.1.8(d)

Typical S/N curves for PH15-7Mo (TH1050), additional data.

Figure 2.6.8.1.8(e)

Typical S/N curves for PH15-7Mo (TH1050), additional data.

Figure 2.6.8.1.8(f)

Typical S/N curves for PH15-7Mo (TH1050), additional data.

2.6.917-4PH

17-4PH is the most widely used martensitic precipitation hardening stainless steel, with nominally 16.5% chromium, 4.25% nickel, 3.6% copper, and 0.3% niobium/columbium. It is available in all common wrought forms and as investment castings.

2.6.9.0Material Specifications and Design Properties

Table 2.6.9.0(a) -” Material Specifications for 17-4PH
Table 2.6.9.0(b) -” Design Mechanical and Physical Properties for 17-4PH (H900)
Table 2.6.9.0(c) -” Design Mechanical and Physical Properties for 17-4PH (H1000)
Table 2.6.9.0(d) -” Design Mechanical and Physical Properties for 17-4PH (H1025)
Table 2.6.9.0(e) -” Design Mechanical and Physical Properties for 17-4PH (H1100)
Table 2.6.9.0(f) -” Design Mechanical and Physical Properties for 17-4PH (H1150)

Figure 2.6.9.0

Effect of temperature on the physical properties of 17-4PH stainless steel.

2.6.9.1H900 Condition

Figure 2.6.9.1.2

Effect of temperature on F_cy for 17-4PH (H900).

Figure 2.6.9.1.3

Effect of temperature on F_su for 17-4PH (H900).

Figure 2.6.9.1.4

Effect of temperature on F_bru for 17-4PH (H900).

Figure 2.6.9.1.8(a)

Typical S/N curves for 17-4PH (H900), unnotched.

Figure 2.6.9.1.8(b)

Typical S/N curves for 17-4PH (H900), notched.

Figure 2.6.9.1.8(c)

Typical S/N curves for 17-4PH (H900), additional data.

2.6.9.2General Temperature Properties (Multiple Conditions)

Figure 2.6.9.2.1

Effect of temperature on F_tu and F_ty for 17-4PH (multiple conditions).

Figure 2.6.9.2.6(a)

Typical stress-strain and tangent-modulus curves for 17-4PH (H900).

Figure 2.6.9.2.6(b)

Typical stress-strain and tangent-modulus curves for 17-4PH (multiple conditions).

2.6.9.3H1000 Condition

Figure 2.6.9.3.6(a)

Typical stress-strain and tangent-modulus curves for 17-4PH (H1000), longitudinal.

Figure 2.6.9.3.6(b)

Typical stress-strain and tangent-modulus curves for 17-4PH (H1000), transverse.

2.6.9.4H1025 Condition

Figure 2.6.9.4.8

Typical S/N curves for 17-4PH (H1025).

2.6.9.5H1100 Condition

Figure 2.6.9.5.8

Typical S/N curves for 17-4PH (H1100).

2.6.9.6H1150 Condition

Figure 2.6.9.6.1

Effect of temperature on F_tu and F_ty for 17-4PH (H1150).

2.6.1017-7PH

17-7PH is a semi-austenitic precipitation hardening stainless steel with nominally 17.0% chromium, 7.1% nickel, and 1.2% aluminum. In the TH1050 condition, the austenite is conditioned at 1400-°F, refrigerated to −100-°F to transform to martensite, then aged at 1050-°F. In the RH950 condition, the austenite is conditioned at 1750-°F, refrigerated to −100-°F, then aged at 950-°F.

2.6.10.0Material Specifications and Design Properties

Table 2.6.10.0(a) -” Material Specifications for 17-7PH
Table 2.6.10.0(b) -” Design Mechanical and Physical Properties for 17-7PH (TH1050)
Table 2.6.10.0(c) -” Design Mechanical and Physical Properties for 17-7PH (RH950)

Figure 2.6.10.0

Effect of temperature on the physical properties of 17-7PH stainless steel.

2.6.10.1TH1050 Condition

Figure 2.6.10.1.1

Effect of temperature on F_tu and F_ty for 17-7PH (TH1050).

Figure 2.6.10.1.2

Effect of temperature on F_cy for 17-7PH (TH1050).

Figure 2.6.10.1.4(a)

Effect of temperature on F_bru for 17-7PH (TH1050), e/D = 1.5.

Figure 2.6.10.1.4(b)

Effect of temperature on F_bru for 17-7PH (TH1050), e/D = 2.0.

Figure 2.6.10.1.6(a)

Typical stress-strain and tangent-modulus curves for 17-7PH (TH1050), longitudinal.

Figure 2.6.10.1.6(b)

Typical stress-strain and tangent-modulus curves for 17-7PH (TH1050), transverse.

Figure 2.6.10.1.6(c)

Typical stress-strain and tangent-modulus curves for 17-7PH (TH1050), short-transverse.

References

2.6.3.1.8Unpublished data on fatigue properties of Custom 450 stainless steel, H900 condition.
2.6.5.0Carpenter Technology Corporation, "Custom 465 Stainless Steel," Product Data Bulletin, Reading, PA.
2.6.6.1.8(a)Unpublished data on fatigue properties of PH13-8Mo stainless steel, H950 condition, unnotched specimens.
2.6.6.1.8(b)Unpublished data on fatigue properties of PH13-8Mo stainless steel, H950 condition, notched specimens.
2.6.6.1.8(c)Unpublished data on fatigue properties of PH13-8Mo stainless steel, H1000 condition.
2.6.6.1.8(d)Unpublished supplemental fatigue data for PH13-8Mo stainless steel.
2.6.7.2.8(a)Unpublished data on fatigue properties of 15-5PH stainless steel, H1025 condition, unnotched specimens.
2.6.7.2.8(b)Unpublished data on fatigue properties of 15-5PH stainless steel, H1025 condition, notched specimens.
2.6.8.1.8(a)Unpublished data on fatigue properties of PH15-7Mo stainless steel, TH1050 condition, sheet specimens.
2.6.8.1.8(b)Unpublished data on fatigue properties of PH15-7Mo stainless steel, TH1050 condition, bar specimens.
2.6.8.1.8(c)Unpublished supplemental fatigue data for PH15-7Mo stainless steel, TH1050 condition.
2.6.9.1.8(a)Unpublished data on fatigue properties of 17-4PH stainless steel, H900 condition, unnotched specimens.
2.6.9.1.8(b)Unpublished data on fatigue properties of 17-4PH stainless steel, H900 condition, notched specimens.

Other MIL-HDBK-5 Chapters

Chapter 1 (General) Chapter 3 (Aluminum)

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