Alloy 625 (UNS N06625)
Description
Alloy 625 is an austenitic nickel-base superalloy with excellent resistance to oxidation and corrosion over a broad range of conditions, including jet engine and chemical process applications. The outstanding strength and toughness of Alloy 625, at temperatures ranging from cryogenic to 2000˚F (1093˚C), are derived primarily from the solid solution strengthening of columbium and molybdenum in a nickel-chromium matrix.
Alloy 625 can be used for parts requiring both corrosion and oxidation resistance up to 2000ºF (1093˚C). AMS 5666 requires a minimum yield strength of 60,000 psi at room temperature for bars under 4 inches in diameter. Mechanical properties for bars 4 inches in diameter and larger are to be agreed upon by purchaser and vendor. This alloy is exceptionally resistant to crevice corrosion and stress corrosion cracking and to chemical attack in both highly oxidizing to moderately reducing conditions. Alloy 625 is virtually immune to corrosion in marine environments and is used extensively in the hot section of jet engines and in high temperature corrosive environments in the chemical processing industry. The alloy has outstanding resistance to creep and stress rupture up to 1200ºF (649˚C), and oxidation and scaling resistance up to 2000ºF (1093˚C).
Chemical Composition
Chemical Composition (wt%) limits as specified in ASTM B446*
Carbon | 0.10 | Silicon | 0.50 |
Chromium | 20.00-23.00 | Phosphorus | 0.015 |
Nickel | 58.00 min | Sulfur | 0.015 |
Molybdenum | 8.00-10.00 | Aluminum | 0.40 |
Iron | 5.00 | Columbium+Tantalum | 3.15-4.15 |
Titanium | 0.40 | Cobalt | 1.00 |
Manganese | 0.50 |
*Maximum, unless range is indicated
Physical Properties
Physical properties for Alloy 625
Density, lb/in3 | 0.305 |
Modulus of Elasticity, psi | 29.8 x 106 |
Coefficient of Thermal Expansion, 68-212˚F, /˚F | 7.1 x 10-6 |
Thermal Conductivity, Btu/ft hr ˚F | 6.3 |
Specific Heat, Btu/lb ˚F | 0.098 |
Electrical Resistivity, Microhm-in | 50.7 |
Mechanical Properties
Mechanical property requirements for heat treated bar product as specified in ASTM B446
Property | Grade 1 (up to 4") |
Grade 1 (over 4") |
Grade 2 |
Yield Strength, min. (ksi) | 60 | 50 | 40 |
Tensile Strength, min. (ksi) | 120 | 110 | 100 |
Elongation, min. (%) | 30 | 25 | 30 |
Standards
Typical standards for Alloy 625
ASTM B446 |
ASME SB446 |
AMS 5666 |
AMS 5665 |