Lecture 6
Nickel and its alloys Subjects of interest • Objectives/Introduction • Production of nickel and nickel alloys • Commercially pure nickel • Nickel-copper alloys (Monels) • Nickel-chromium alloys • Nickel-base superalloys • Single crystal castings of nickel-base superalloys
Suranaree University of Technology
Tapany Udomphol
May-Aug 2007
Objectives • This chapter provides fundamental knowledge of different methods of productions of nickel alloys and the use of various types of nickel alloys. • The influences of alloy composition and microstructure on chemical and mechanical properties of nickel alloys will be discussed in relation to its applications.
Suranaree University of Technology
Tapany Udomphol
May-Aug 2007
Introduction Properties • Silvery shiny appearance • High toughness and ductility • Good high and low temperature strength • High oxidation resistance • Good corrosion resistance • Ferro-magnetic Limitations • Relatively high cost • Not mixed with cheap alloying elements.
Suranaree University of Technology
FCC
28
Ni Nickel
58.71 Crystal structure Atomic number Atomic weight Density (g.cm-3) Melting point (oC)
Tapany Udomphol
FCC 28 58.71 8.89 1455
May-Aug 2007
Applications • Applications required necessary corrosion or heat- resisting properties and for special engineering applications. • Chemical plant, heat exchanger, reaction furnace, rotary kiln, turbine blades. • Used as alloying elements in stainless steels, and in other elements such as copper, cobalt, chromium, etc.
Reaction furnace
Heat exchangers
www.msm.cam.ac.uk
Turbine blades www.immnet.com
Aerospace flow bodies Suranaree University of Technology
Rotary kiln Tapany Udomphol
May-Aug 2007
Production of nickel First discovery of nickel mineral by the German was mistakenly misunderstood to be rich-copper mineral. There are three major types of nickel deposits (sources): 1) Nickel-copper sulphide 2) Nickel silicates 3) Nickel laterites and serpentines home.arcor.de
www.mii.org
Nickeline or niccolite
research.eas.ualberta.ca/ egg/nilaterite.jpg
Nickel laterite deposits Suranaree University of Technology
Serpentine deposits
Tapany Udomphol
May-Aug 2007
Extraction of nickel Iron ore recovery plant
Pure nickel and other nickel alloy products
Nickel-sulphide ore (Fe, Cu)
Crushing Iron sulphide (pyrrhotite concentrate)
Nickel refinery Copper smelter
Grinding
Different grade of nickel oxides
Magnetic separation Remaining ore (Ni, Cu)
Roasting Froth flotation treatment Copper sulphide
Nickel concentrate
Nickel sulphide
Copper concentrate Froth flotation
Roasting Cooling (Reverberatory furnace) Smelting Bessemer matte (Ni and Cu sulphides) Suranaree University of Technology
Recrystallisation
Crushing & grinding
Crystals of Ni and Cu sulphides. Ni-Cu metallic alloy Tapany Udomphol
May-Aug 2007
Classification of nickel alloys There are different types of nickel and nickel alloys;
1) Commercially pure nickel 2) Nickel-copper alloys (Monels) 3) Nickel-chromium alloys 4) Nickel-base superalloys 5) Nickel-iron superalloys
Suranaree University of Technology
Tapany Udomphol
May-Aug 2007
Commercially pure nickel • High purity nickel contains 99.99% Ni. • Commercially pure nickel contains 99.5% Ni (+Co). • Microstructure consists of solid solution phase in annealed condition. 100 x
Properties • Good mechanical properties and retains its strength at elevated temperature. • Excellent resistance to most corrosive environment.
Suranaree University of Technology
Cold drawn Nickel 200 annealed at 829oC
Applications • Food processing equipment • Electrical & electronic parts • Caustic handling equipment.
Tapany Udomphol
May-Aug 2007
Nickel-copper alloys (Monels) • Ni and Cu form complete solid solution. • Most important Ni-Cu alloy contains 67%Ni and 33%Cu, called Monels. Properties • High strength and toughness over a range of temperature. • Good weldability • Excellent corrosion resistance
Ni-Cu phase diagram
Applications • Values, pumps, marine fixtures and fasteners. • Chemical processing equipment. • Oil-well drill collars and instruments. 250 x Suranaree University of Technology
Tapany Udomphol
Microstructure of cold drawn Monel R405 and annealed at 829oC, showing solid solution phase of Ni-Cu with sulphide stringers (black) May-Aug 2007
Nickel-chromium alloys • Cr forms solid solution with Ni up to~30% at RT. High corrosion resistance is due to high Cr addition. • Inconel 600 (15.5%Cr, 8%Fe) is a standard engineering alloy. Other Ni-Cr alloys are Inconel 601 and 625 with improved properties. Properties Ni-Cr phase diagram
• High corrosion resistance at high temperature. • High strength and workability. Applications • Heat exchanger tubing • Chemical and food processing equipment. • Furnace muffle. Suranaree University of Technology
1500 x Tapany Udomphol
Inconel 600, solution heat-treated at 1200oC/1h+870oC/4h, showing solid solution phase with chromium carbide precipitates at GBs and some titanium carbides and nitrides within the grains May-Aug 2007
Nickel-base superalloys • High temperature heat-resistance alloys, which can retain high strengths at elevated temperatures. • There are three types of Ni-base superalloys; nickel base, nickeliron base and cobalt base. The alloys contain high Cr with Ti, Al to from precipitates and additions of Mo, Co, Nb, Zr, B, Fe. • Microstructures are complex. Properties • Heat resistant and high strength at high temperature (760-980oC). • Good corrosion resistance. • Good oxidation resistance. Applications • Aircrafts, space vehicles, rocket engines • Industrial gas turbines, high temp applications. • Nuclear reactors, submarines. • Steam power plants, petrochemical equipment. Suranaree University of Technology
Tapany Udomphol
www.stratcor.com
May-Aug 2007
Microstructure of nickel base superalloys
Carbides at GB
10,000 x Complex microstructure of astroloy forging after heat treatments
The major phases present in the nickel-base superalloys:
1) γ (gamma) phase – the continuous matrix of FCC austenite. 2) γ’ (gamma prime) phase – the major precipitate phase (more cubic shape). 3) Carbides –various types, mainly M23C6 and MC. M = metal. Note: GB carbides affect high-temp strength, ductility, creep. Suranaree University of Technology
Tapany Udomphol
May-Aug 2007
Nickel- iron superalloys • Fe is added to replace some of Ni as it has lower cost. lowering the properties as compared with nickel base superalloy. therefore it is used at lower temperatures. • Ni-Fe superalloys contains 25-45%Ni and 15-60%Fe. • Higher Ni content increases operating temp (upto 815oC), due to improved stability but more costly. • Ex: Inconel 707, 718, 901. • Microstructure consists of austenistic FCC matrix and can be strengthened by solid solution strengthening (Mo, Cr), and precipitation hardening (Ti, Nb, Al) by forming intermetallic phases.
Suranaree University of Technology
15,000 x Optical micrograph of SEM micrograph of Inconel 718 Inconel 901 after after exposure at 705oC/6,048 precipitation hardening h, 37 ksi Tapany Udomphol
May-Aug 2007
Single-crystal castings of nickel-base superalloys • A major increase in strength and temperature capability of superalloy casting has been much improve with the introduction of columnar-grained and single crystal casting.
Competitive grain Diagram of setup for single crystal casting
Simulation of evolution of grain structure in a single crystal casting. Turbines blades are cast using a spiral starter www.nap.edu
Suranaree University of Technology
www.msm.cam.ac.uk
Tapany Udomphol
May-Aug 2007
Applications of single-crystal castings of nickel-base superalloys • Used in production of aerofoils, gas turbine engines, which allow the operating temperature range ~ 50oC higher than normal materials. Property comparison between polycrystal, columnar crystal and single crystal
(a) Polycrystal
(b) Columnar crystal
(c) Single crystal
Single crystal casting of superalloy
www.grc.nasa.gov Suranaree University of Technology
Tapany Udomphol
May-Aug 2007
References • , กก ก, 2536, ก
ก !"
", ISBN 974-582-155-1. • Smith, W.F., Structure and properties of engineering alloys, second edition, 1993, McGraw-Hill, ISB 0-07-59172-5. • www.cda.org.uk. • Heußner, U., Nickel alloys, 1998, Marcel Dekker, Inc., ISBN 0-8247-0440-1.
Suranaree University of Technology
Tapany Udomphol
May-Aug 2007
