Enhanced Fatigue Resistant Alloy 625M Sheet / Strip / Foil For Aerospace Exhaust

Enhanced fatigue resistant Alloy 625M (N06626) sheet, strip, foil, fitting, tube for aerospace exhaust etc

1 PRODUCT

Enhanced fatigue resistant Alloy 625M (UNS N06626) for aerospace exhaust etc.

Product forms available as sheet, strip, foil, fitting, tube etc.

2 EQUIVALENT DESIGNATION

UNS N06626, W.Nr.2.4856(EN), Inconel^® alloy 625LCF,Haynes® 625SQ^® alloy

3 APPLICATION

Alloy 625M is readily fabricated and welded using practices common to Alloy 625. Alloy 625M sheet and strip find application in aerospace exhaust, automotive flexible coupling bellows, expansion joints in process or transport piping, and chemical process industry bellow, expansion joints, and fabrications where low-cycle and thermal fatigue at up to 1200°F (650°C) resistance, strength, and corrosion resistance are required.

4 OVERVIEW

Alloy 625M is a solid-solution strengthened superalloy, a modification of Alloy 625 developed to enhance resistance to fatigue at temperatures up to approximately 1200°F (649°C). The alloy composition is tightly controlled to very low levels of carbon, silicon, and nitrogen.

Primary melting is by vacuum induction melting, followed by consumable electrode practice using electroslag remelting. During processing, the grain size is controlled to ASTM #5 or finer.

5 CHEMICAL COMPOSITION (wt%):

Table 1

6 PHYSICAL PROPERTIES

Table 2 Physical constants

7 MECHANICAL PROPERTIES

Alloy 625M has an average grain size of ASTM No. 5 (0.0025 in/0.064 mm) or finer. The outstanding characteristic of this alloy is its low-cycle fatigue strength derived primarily from controlled microstructure, grain size and yield strength.

The same factors that enhance resistance to mechanical fatigue also improve resistance to thermal fatigue. The alloy, like Alloy 625, undergoes a microstructural phase formation during long-time exposure to intermediate elevated temperatures. Such exposure can increase the strength of the alloy while lowering ductility and impact properties. Because of the phase formation, with the unfavorable effect of fine grain on creep-rupture properties, Alloy 625M is not recommended for extended use at high stress levels above 1200°F (650°C).

Room temperature mechanical properties

Table 3 Room temperature mechanical properties^a

^a Yield strength requirement may not apply to sheet thickness under 0.010 in (0.25 mm). Elongation requirement may not apply to thicknesses under 0.005 in (0.13 mm). All requirements are at room temperature.

Bend Tent:

Thicknesses of 0.050 in (1.27 mm) and under: 1T

Thicknesses over 0.050 in (1.27 mm) through 0.100 in (2.54 mm): 2T

Table 4 High temperature mechanical properties

Table 5 ASTM grain size numbers for various annealing temperatures on cold rolled sheet

8 HEAT TREATMENT

Alloy 625M is typically annealed at 1800°F (980°C) for 5 minutes with air cooling.

Sheet and Strip, AMS 5879

1600°F (871°C) Minimum/Bright Anneal

9 WORKING INSTRUCTION

Alloy 625M can readily be hot- and cold-worked and machined. However, machines are required for any operation that meet the high mechanical properties.

Hot working

Alloy 625M may be hot worked in the temperature range 1176 to 900°C (2150 to 1650°F) with subsequent rapid cooling down in water or by using air. The workpieces should be placed in the furnace heated to hot working temperature in order to heat up. Once the hot working temperature has been reached again, a retention time of 60 minutes for each 100 mm (4 in) of workpiece thickness is recommended. Afterwards, workpieces should be removed immediately and formed during the stated temperature window. If the material temperature falls to 950°C (1742°F), the workpiece must be reheated.

Cold working

Cold working should be carried out on annealed material. Alloy 625M has a higher work hardening rate than austenitic stainless steels. This must be taken into account during design and selection of forming tools and equipment and during the planning of the forming processes. Intermediate annealing may be necessary at high degrees of cold working deformation. After cold working with more than 15 % of deformation the material should be soft annealed or solution annealed.

Machining

Alloy 625M should be machined in the annealed condition. As the alloy is prone to work-hardening, low cutting speeds and appropriate feed rates should be used and the tool should be engaged at all times. Sufficient chip depths are important to get below the work-hardened surface layer. The optimum dissipation of heat through the use of large amounts of appropriate, preferably water containing cooling lubricants is crucial for a stable machining process.

Table 6 Recommended conditions for turning with single point tools

10 STANDARD SPECIFICATION

Alloy 625M is designated as UNS N06626 and W. Nr. 2.4856, and meets the requirements for UNS N06625.

Sheet and strip

SAE AMS 5879 Nickel Alloy, Corrosion and Heat-Resistant, Sheet, Strip, and Foil, 62Ni - 21.5Cr - 9.0Mo - 3.7Cb, Cold Rolled and Annealed

ASTM B443 / ASME SB443

BS 3072 (NA21)

ASME Code Case 2276.

Welded pipe and tube

ASME Code Case 2276.

Fittings

ASME Code Case 2276.

11 COMPETITIVE ADVANTAGE

(1) More than 50 years experience of research and develop in high temperature alloy, corrosion resistance alloy, precision alloy, refractory alloy, rare metal and precious metal material and products.
(2) 6 state key laboratories and calibration center.
(3) Patented and innovative technologies.

(4) Ultra-purity smelting process: VIM + IG-ESR + VAR

(5) Excellent high performance.

12 BUSINESS TERM