Nickel
Nickel alloys can offer enhanced corrosion resistance, toughness, strength at high and low temperatures, and interesting magnetic, thermal and electronic properties compared with other metals. Due to their higher nickel content compared with stainless steels, they can be appreciably more expensive, but find uses in more demanding applications from gas turbines to chemical plants and oil & gas industry components.
Nickel-Copper Alloys – Monel®
Nickel – copper alloys such as Alloy 400 and Alloy K-500, also known as Monel K500, (Special Metals Corporation’s family of Nickel-Copper alloys is known as Monel®) are based predominantly on nickel and copper, with smaller additions of manganese and iron. They are used where a higher strength is required compared to pure nickel, and resist corrosion in a wide range of environments. They can be fabricated readily by hot and cold working, machining, and welding. Nickel-Copper alloys find wide application in oil refining and marine applications where long corrosion-free life is required. Due to the good thermal conductivity of the alloys, they are also frequently used for heat exchangers where sea water is one of the fluids concerned.
Nickel-Iron-Chromium Alloys – Incoloy®
Nickel-Iron-Chromium alloys such as Alloy 825, also known as Incoloy 825, (Special Metals Corporation’s family of Nickel-Iron-Chrome alloys is known as Incoloy® ) were developed to provide a more cost-effective solution for applications requiring high-temperature and corrosion resistance – achieved by lowering the nickel content. Selectively alloying with other elements can greatly improve their performance in certain environments. For instance, Alloy 825 also contains molybdenum and copper to improve resistance to strongly reducing environments, such as those containing sulphuric and phosphoric acids.
Nickel-Chromium Super Alloys – Inconel®
Nickel-Chromium super alloys such as Alloy 625, also known as Inconel 625, and Alloy 718, also known as Inconel 718, (Special Metals Corporation’s family of Nickel-Chromium alloys is known as Inconel®) are typically used in high-temperature applications. When heated, they form a thick and stable passivating oxide layer protecting the surface from further attacks. These alloys retain their strength over a wide temperature range, particularly at elevated temperatures where aluminium and steel would otherwise succumb to creep failure. Varying levels of high-temperature strength can be developed by solid solution strengthening or precipitation strengthening (with niobium additions).
| Alloy | Common Name | Related Specifications | Tensile Strength | Proof Test | Elongation | ||
| British | European | United States | N/mm2 (ksi) | N/mm2 (ksi) | (%) | ||
| Alloy 925 | UNS N09925 | UNS N09925 |
ASTM B805 API 6A CRA NACE MR0175-3 |
965 (140) | 758 - 965 (110 - 140) | 18 | |
| Alloy 825 HS110 | UNS N08825 110ksi | BS 3076 NA16 |
2.4858 |
ASTM B425 UNS N08825 |
793 (115) | 758 (110) | 30 |
| Alloy 825 (Tube) | UNS N08825 | BS 3076 NA16 |
2.4858 |
ASTM B425 UNS N00825 |
518 (75) | 241 (35) | 30 |
| Alloy 825 | UNS N08825 | BS 3076 NA16 |
2.4858 |
ASTM B425 UNS N08825 |
590 (85) | 220 (32) | 30 |
| Alloy 725 | UNS N07725 | ASTM B637 UNS N07725 |
1137 (165) | 827 (125) | 20 | ||
| Alloy 718 | UNS N07718 | 2.4668 |
ASTM B637 UNS N07718 API 6A 718 |
1138 (165) | 965 (140) | 20 | |
| Alloy 625 | UNS N06625 | BS 3076 NA21 |
2.4856 |
ASTM B564 B466 UNS N06625 |
830 (120) | 415 (60) | 30 |
| Alloy K500 | UNS N05500 | 965 (140) | 724 (105) | 20 | |||
| Alloy 400 | UNS N04400 | BS 3076 NA13 |
2.4360 |
ASTM A164 UNS N04400, N04405 QQ - N - 281 |
483 (70) | 172 (25) | 35 |
Alloy 925:
Alloy 925 is a precipitation-hardenable Nickel-Iron-Chromium Alloy with additions of Molybdenum, Copper, Titanium and Aluminium, supplied in the solution annealed and aged condition. The Titanium and Aluminium are specifically added to give a strengthening of the alloy during ageing, as Ni3(Al, Ti) gamma (‘ϒ’) prime precipitates form throughout the alloy matrix and greatly increases the hardness and strength in a similar way to Alloy K500, 718 and 725.
Alloy 825 HS110:
Alloy 825 HS110 is a high strength nickel-iron-chromium alloy with additions of molybdenum, copper and titanium (NiCr21Mo), supplied in the hot worked, annealed and cold worked condition. Controlled cold working ensures that the product achieves significantly increased yield strengths over the annealed product, whilst retaining good ductility and toughness.
Alloy 825 (Tube):
Alloy 825 is a nickel-iron-chromium alloy with additions of molybdenum, copper and titanium (NiCr21Mo), supplied in the hot worked and annealed condition. It achieves good mechanical properties from cryogenic to medium-high temperatures (5400C) and can be significantly strengthened through cold working.
The high nickel content ensures resistance to stress corrosion cracking, combined with molybdenum and copper to strongly resist reducing environments such as sulphuric and phosphoric acids, chromium to resist oxidising environments such as nitric acid, titanium to inhibit intergranular corrosion, and overall resistance to pitting and crevice corrosion.
Alloy 825:
Alloy 825 is a nickel-iron-chromium alloy with additions of molybdenum, copper and titanium (NiCr21Mo), supplied in the hot worked and annealed condition. It achieves good mechanical properties from cryogenic to medium-high temperatures (5400C) and can be significantly strengthened through cold working.
The high nickel content ensures resistance to stress corrosion cracking, combined with molybdenum and copper to strongly resist reducing environments such as sulphuric and phosphoric acids, chromium to resist oxidising environments such as nitric acid, titanium to inhibit intergranular corrosion, and overall resistance to pitting and crevice corrosion.
Alloy 725:
Alloy 725 is a nickel-chromium alloy with significant additions of molybdenum, niobium and titanium, supplied in the hot worked, annealed and age-hardened condition. It is age-hardened to achieve extremely high strength, approximately twice that of Alloy 625 in the annealed condition, through the precipitation of ϒ” phase during a controlled heat treatment process. As this high strength is achieved by ageing rather than cold working, it retains excellent ductility and toughness, and this approach is useful for large or non-uniform sections that cannot be strengthened through cold working.
Alloy 718:
Alloy 718 is a high-strength, corrosion-resistant nickel chromium alloy supplied in the hot worked, solution annealed and age hardened condition. The addition of Nb, Ti, Al and Ni form a series of precipitates during the controlled solution annealing and ageing process steps, resulting in a significant increase in strength and hardness compared with alternative nickel alloys. These tensile and creep rupture properties are maintained from cryogenic to elevated temperatures, making it suitable for applications between -250oC – 750oC.
Alloy 625:
Alloy 625 is a nickel-chromium-molybdenum-niobium alloy (NiCr22Mo9Nb), supplied in the hot worked and annealed condition. It achieves high-strength levels from the solid solution effects of Molybdenum and Niobium (Colombium) from room temperature up to 800°C.
It is particularly useful in situations where oxidation resistance and avoidance of pitting is required. In the annealed condition, it is fully austenitic and is suitable for machining. It provides excellent corrosion resistance in a wide variety of severe corrosive environments due to its high alloy content.
Alloy K500:
Alloy K500 is a precipitation-hardenable nickel-copper alloy. Although Langley Alloys supply Alloy K500 in all conditions, we predominantly supply material in the Hot Worked and Precipitation Treated condition, which offers the optimum combination of high strength and ductility across the size range. The increased properties are obtained by adding aluminium and titanium to the nickel-copper base, and by heating under controlled conditions so that particles of ‘ϒ’ Ni3 (Ti, Al) are precipitated throughout the matrix. The thermal processing used to effect precipitation is commonly called age hardening or ageing.
Alloy 400:
Alloy 400 is a nickel-copper single-phase alloy most commonly supplied in hot worked and annealed condition. Although the grade can be tempered or cold worked to increase its properties, in its standard annealed condition it is easy to form and fabricate with no requirements for additional heat treatments to re-balance the alloy. It retains excellent mechanical properties at sub-zero temperatures. Strength and hardness increase with only a slight loss of ductility and impact resistance.