Alloy K500,Monel K500 Rod,UNS N05500

Alloy K500,Monel K500 Wire,UNS N05500

Introduction to Alloy K500 (Monel K500 Wire, UNS N05500)

Alloy K500, commercially known as Monel K500 and classified under UNS N05500, is a precipitation-hardening nickel-copper superalloy that builds on the exceptional corrosion resistance of the classic Monel 400 alloy while adding significant strength via controlled age hardening. Its unique chemistry combines a nickel-copper matrix (for resistance to seawater, acids, and alkalis) with aluminum and titanium (which form strengthening gamma-prime, γ′, Ni₃(Al,Ti) precipitates), enabling it to operate reliably from cryogenic conditions (-253°C/-423°F) up to 480°C/900°F. Unlike non-hardening Monel alloys, Alloy K500 achieves tensile strengths over 1000 MPa after aging, making it ideal for applications requiring both corrosion resistance and high structural integrity. Monel K500 wire, a key form of this alloy, is widely used in marine engineering, oil & gas, chemical processing, and aerospace industries—excelling in components like subsea fasteners, downhole tools, and precision springs that endure harsh corrosive environments and mechanical stress.

1. Chemical Composition (Typical, wt%)

The chemical composition of UNS N05500 adheres to strict industry standards including ASTM B865 (for nickel-copper alloy wire), ASTM B564 (for nickel-copper alloy forgings), and ASME SB865, ensuring consistent precipitation-hardening behavior, corrosion resistance, and mechanical performance. The typical composition is as follows:

Element

Content Range (wt%)

Function

Nickel (Ni)

63.0 - 67.0

Serves as the primary matrix element, stabilizing the austenitic structure; enhances resistance to reducing environments (e.g., hydrogen sulfide, sulfuric acid) and forms the base for γ′ precipitate formation.

Copper (Cu)

27.0 - 33.0

A key alloying element that boosts corrosion resistance in seawater, brines, and organic acids; improves ductility and workability during wire fabrication.

Aluminum (Al)

2.3 - 3.1

Critical for precipitation hardening—combines with nickel to form γ′ (Ni₃Al) precipitates, the main contributor to high tensile and yield strength; refines grain structure to enhance toughness.

Titanium (Ti)

0.35 - 0.85

Cooperates with aluminum to optimize γ′ precipitate size and distribution; prevents over-aging and maintains strength at elevated temperatures (up to 480°C); enhances resistance to stress corrosion cracking (SCC).

Iron (Fe)

≤ 2.0

Improves hot workability (critical for wire rod production) and controls alloy cost; limited to avoid compromising corrosion resistance in marine environments.

Manganese (Mn)

≤ 1.5

Aids in deoxidation during melting and improves cold workability for fine wire drawing; controlled to avoid brittleness at low temperatures.

Silicon (Si)

≤ 0.5

Reduces oxide formation during hot processing and improves molten alloy fluidity for casting; limited to avoid excessive inclusions that degrade fatigue life.

Carbon (C)

≤ 0.10

Minimized to prevent carbide precipitation at grain boundaries, which can reduce corrosion resistance and cause intergranular cracking in corrosive media.

Sulfur (S)

≤ 0.010

Strictly limited to prevent hot cracking during wire drawing and welding; reduces the risk of pitting corrosion in sulfur-rich environments (e.g., sour gas wells).

Phosphorus (P)

≤ 0.015

Controlled to avoid grain boundary embrittlement, especially in components exposed to cyclic loading or cryogenic temperatures.

Cobalt (Co)

≤ 1.0

Trace element that slightly enhances high-temperature strength without interfering with γ′ precipitate formation; limited to avoid increasing alloy cost.

2. Physical Properties

Monel K500 wire exhibits distinct physical properties before and after age hardening, with post-aging performance optimized for strength and corrosion resistance. Key properties (measured at room temperature unless specified otherwise) are:

Property

Value (Annealed)

Value (Aged)

Test Condition

Density

8.47 g/cm³

8.47 g/cm³

Room temperature (25°C)

Melting Point Range

1300 - 1350°C

1300 - 1350°C

-

Thermal Expansion Coefficient

13.1 × 10⁻⁶/°C

13.1 × 10⁻⁶/°C

20 - 100°C; 15.9 × 10⁻⁶/°C (20 - 400°C)

Thermal Conductivity

22.0 W/(m·K)

22.0 W/(m·K)

100°C; 28.5 W/(m·K) (400°C)

Electrical Resistivity

0.52 × 10⁻⁶ Ω·m

0.55 × 10⁻⁶ Ω·m

Room temperature (25°C)

Modulus of Elasticity

180 GPa

190 GPa

Room temperature (tensile)

Poisson’s Ratio

0.32

0.32

Room temperature

Curie Temperature

≈ -196°C

≈ -196°C

Below this temperature, weakly ferromagnetic.

Tensile Strength

≥ 650 MPa

≥ 1035 MPa

Room temperature; ≥ 700 MPa (400°C, aged)

Yield Strength (0.2% Offset)

≥ 275 MPa

≥ 860 MPa

Room temperature; ≥ 600 MPa (400°C, aged)

Elongation

≥ 40%

≥ 15%

Room temperature

Hardness

≤ 180 HB

30 - 38 HRC

Room temperature

Impact Toughness (Charpy V-Notch)

≥ 120 J

≥ 40 J

Room temperature; ≥ 30 J (-196°C, aged)

3. Production Process of Monel K500 Wire

The manufacturing of Monel K500 wire requires precise control of aluminum and titanium content (for γ′ precipitation) and strict heat treatment to balance strength and corrosion resistance. Key steps include:

3.1 Raw Material Melting & Casting

Melting: High-purity raw materials (nickel, copper, aluminum, titanium, etc.) are melted via vacuum induction melting (VIM) followed by vacuum arc remelting (VAR). This dual process eliminates gaseous impurities (O₂ < 20 ppm, N₂ < 30 ppm) and ensures uniform distribution of aluminum and titanium—critical for consistent γ′ precipitate formation.

Casting: Molten alloy is cast into ingots (500 - 2500 kg) or blooms, which undergo homogenization annealing at 1050 - 1100°C for 8 - 10 hours. This step eliminates chemical segregation (especially of aluminum and titanium) and dissolves coarse intermetallic phases, preparing the material for hot working.

3.2 Hot Working & Wire Rod Production

Hot Rolling: Ingots/blooms are hot-rolled at 950 - 1050°C into wire rods (diameter: 8 - 20 mm). Hot rolling breaks down coarse grains and improves workability; rods are air-cooled to room temperature to avoid premature precipitation of γ′ (which would reduce ductility during cold drawing).

Descaling: Hot-rolled rods undergo shot blasting (to remove loose oxide scale) followed by acid pickling (nitric-hydrofluoric acid solution) to eliminate residual copper-nickel oxide layers. This step prevents surface defects during cold drawing and ensures clean alloy surfaces for corrosion resistance.

3.3 Cold Drawing (Wire Formation)

Multi-Pass Cold Drawing: Wire rods are cold-drawn through diamond dies in 6 - 10 passes to achieve the desired diameter (typically 0.1 mm - 10 mm). Each pass reduces diameter by 12 - 20%, with intermediate annealing (950 - 1000°C for 30 - 45 minutes, water-quenched) between passes. This annealing step relieves work hardening, restores ductility, and dissolves any unintended γ′ precipitates—ensuring uniform drawing performance.

Dimensional Control: Tension, die alignment, and drawing speed are precisely regulated to maintain tight diameter tolerance (±0.015 mm for precision wire) and roundness (≤0.008 mm). For applications like subsea springs or medical devices, laser diameter monitoring ensures consistency, as dimensional variations can affect load-bearing capacity.

3.4 Age Hardening (Strength Optimization)

Age hardening is the core step to activate γ′ precipitates and achieve target strength. The process follows a standardized two-stage cycle (per ASTM B865):

Solution Annealing: Heating the wire to 980 - 1020°C for 1 - 2 hours, followed by rapid water quenching. This step ensures a uniform austenitic microstructure and dissolves all existing precipitates, setting the stage for controlled γ′ formation.

Final Aging: Heating the wire to 450 - 480°C for 12 - 16 hours, then air cooling. This step promotes the nucleation and growth of fine, evenly distributed γ′ precipitates (5 - 10 nm), maximizing strength while preserving sufficient ductility and corrosion resistance.

Note: For ultra-fine wire (diameter < 0.5 mm), aging time is reduced to 8 - 12 hours to avoid excessive hardening, which could compromise flexibility for applications like sensor wires.

3.5 Surface Finishing & Quality Inspection

Surface Treatment:

Pickling: Post-aging pickling in nitric acid to remove oxide scales and enhance the natural corrosion-resistant film of nickel-copper.

Passivation: Optional chromate treatment to further strengthen the surface film, ideal for marine or sour gas applications exposed to chloride ions.

Polishing: For high-precision applications (e.g., aerospace fasteners, medical instruments), the wire is polished to a smooth surface finish (Ra ≤ 0.2 μm) using electrochemical or mechanical polishing, minimizing stress concentrations.

Quality Control:

Chemical Analysis: Optical emission spectroscopy (OES) to verify aluminum and titanium content (within 2.3-3.1% and 0.35-0.85%, respectively) for proper γ′ formation.

Mechanical Testing: Tensile testing (pre- and post-aging) to confirm strength and elongation; hardness testing (HRC) to validate aging effectiveness; fatigue testing (for cyclic-loading components like springs).

Corrosion Testing: Salt spray testing (ASTM B117), seawater immersion testing (ASTM G31), and stress corrosion cracking testing (ASTM G36) to validate resistance to harsh environments.

Non-Destructive Testing: Eddy current testing (for surface defects like cracks or pits) and ultrasonic testing (for internal flaws)—critical for downhole or subsea components.

Microstructural Analysis: Optical microscopy to confirm γ′ precipitate distribution and grain size (ASTM 5 - 7), ensuring consistency across production batches.

4. Product Applications

Monel K500 wire’s unique combination of high strength, exceptional corrosion resistance, and cryogenic toughness makes it indispensable in industries requiring performance in harsh, corrosive, and high-stress environments:

4.1 Marine Engineering

Subsea Components: Fine wire (0.3 - 2.0 mm) for subsea mooring line tensioners, ROV (Remote Operated Vehicle) manipulator springs, and underwater fasteners—resists seawater corrosion (3.5% NaCl) and biofouling, even at depths up to 3000 meters.

Naval Vessels: Wire for propeller shaft bearings, hull fasteners, and heat exchanger tubes—outperforms stainless steel in saltwater, reducing maintenance costs and extending service life.

Coastal Infrastructure: Wire for corrosion-resistant fencing, bridge cables, and offshore wind turbine foundation components—resists salt spray and tidal corrosion.

4.2 Oil & Gas Industry

Downhole Tools: Wire for logging tool springs, valve stems, and electrical conductors in sour gas wells—withstands H₂S (up to 1000 ppm) and chloride-rich brines at temperatures up to 400°C, avoiding stress corrosion cracking.

Offshore Platforms: Wire for riser tensioner springs and pipeline fasteners—resists marine atmospheric corrosion and cyclic loading from waves and currents.

Refining Equipment: Wire for catalyst support grids and sensor probes in crude oil refining—resists sulfuric acid and hydrocarbon-induced corrosion.

4.3 Chemical & Petrochemical Industry

Corrosive Process Equipment: Wire for agitator springs, thermocouple sheaths, and filter mesh in sulfuric acid (H₂SO₄), acetic acid, and ammonia production—resists both oxidizing and reducing acids.

Pharmaceutical Manufacturing: Sanitary wire for mixing blades and filtration systems—complies with FDA standards (21 CFR Part 177) for food/drug contact and resists cleaning agents like sodium hydroxide.

4.4 Aerospace & Defense

Aerospace Fasteners: Wire for high-strength rivets and bolts in aircraft landing gear—combines lightweight properties with resistance to hydraulic fluid corrosion and temperature cycles (-50°C to 150°C).

Missile Systems: Wire for guidance system actuators and control springs—maintains strength and dimensional stability under extreme G-forces and thermal cycling.

Cryogenic Applications: Wire for liquid oxygen (LOX) and liquid hydrogen (LH₂) tank fasteners—retains toughness at -196°C without brittle fracture.

4.5 Medical Devices

Surgical Instruments: Ultra-fine wire (0.05 - 0.2 mm) for laparoscopic tools and orthopedic implant screws—biocompatible (ISO 10993), resists bodily fluid corrosion, and provides sufficient strength for load-bearing applications.

Diagnostic Equipment: Wire for catheter sensors and endoscope components—flexible yet strong, enabling precise movement within the human body.

Conclusion

Alloy K500 (Monel K500 Wire, UNS N05500) is a premier precipitation-hardening nickel-copper superalloy wire, distinguished by its rare balance of exceptional corrosion resistance and high strength. Its ability to withstand harsh environments—from deep seawater to sour gas wells—while maintaining structural integrity makes it a critical material for marine, oil & gas, and aerospace industries. The precise control of its manufacturing process, especially aluminum/titanium content and age hardening, ensures consistent performance across applications. For custom requirements—such as ultra-precision wire (down to 0.01 mm diameter), specialized surface finishes (e.g., electropolishing), or tailored aging cycles for specific strength-ductility balances—manufacturers offer customized solutions to meet the most demanding corrosion and stress challenges.

Packing of Standard Packing:

 Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 701 gallon liquid totes Special package is available on request.