Nicrofer 6025HT Product Introduction
Product Overview
Nicrofer 6025HT (UNS N06025) is a high-chromium nickel-based superalloy engineered for extreme high-temperature environments requiring superior oxidation, carburization, and corrosion resistance. Unlike aerospace-focused Nimonic 263 (Ni-Cr-Co, optimized for creep in gas turbines) or Incoloy 800HT (Ni-Fe-Cr, medium-temperature load-bearing), Nicrofer 6025HT features a tailored high-chromium composition (24-26% Cr) combined with aluminum (1.0-1.8%) and silicon (0.8-1.5%)—a design that forms a dense, self-healing Al₂O₃-Cr₂O₃-SiO₂ composite oxide film, enabling stable service at temperatures up to 1100℃. It retains good creep rupture strength (e.g., 800℃/10,000-hour creep strength ≥120 MPa) and resists carbon penetration in carburizing atmospheres, making it the industry standard for industrial furnace components, heat treatment equipment, and metallurgical processes—where “high-temperature oxidation resistance + anti-carburization + long-term durability” are critical.
International Grade Comparison
Standard System | Grade | Description |
ASTM (USA) | N06025 | UNS Unified Numbering System Grade (exclusive for Nicrofer 6025HT) |
EN (EU) | NiCr25FeAlSi | EN 10088-1 Standard Grade (high-temp oxidation-resistant alloy) |
DIN (Germany) | 1.4886 | DIN 17750 Standard Grade (classic high-Cr Ni-based heat-resistant alloy) |
JIS (Japan) | NW06025 | JIS G4902 Standard Grade (equivalent to Nicrofer 6025HT) |
ISO (International) | NiCr25FeAlSi | ISO 6363 Standard Grade (industrial high-temp corrosion-resistant alloy) |
Physical Properties (Room Temperature & High-Temperature Highlights)
Property Indicator | Typical Value (Room Temp) | Unit | High-Temperature Performance Advantage |
Tensile Strength | ≥650 | MPa | 800℃ tensile strength: ≥480 MPa; 1000℃: ≥220 MPa |
Yield Strength (0.2% Offset) | ≥300 | MPa | 800℃ yield strength: ≥320 MPa; no brittle softening up to 1050℃ |
Elongation (50mm Gauge Length) | ≥30 | % | Retains ≥15% elongation at 900℃ |
Creep Rupture Strength (800℃/10,000h) | ≥120 | MPa | Exceeds Incoloy 800HT in carburizing environments |
Density | 8.35 | g/cm³ | Slightly higher than Ni-Fe-Cr alloys (e.g., Incoloy 800: 8.0 g/cm³) |
Melting Point | 1370-1420 | ℃ | Stable above typical industrial furnace temps (800-1100℃) |
Oxidation Rate (1100℃/1000h) | ≤0.1 | mm/year | 50% lower than Nimonic 263 in oxidizing atmospheres |
Chemical Composition (Mass Fraction, High-Temp Corrosion-Optimized)
Chemical Symbol | Composition Range (%) | Role in High-Temperature Performance |
Ni | Balance (≥60) | Stabilizes face-centered cubic (FCC) austenitic matrix; resists phase transformation at high temps |
Cr | 24.0-26.0 | Core anti-oxidation element; forms dense Cr₂O₃ film to block oxygen penetration |
Fe | 5.0-9.0 | Optimizes cost-effectiveness; improves hot workability |
Al | 1.0-1.8 | Forms Al₂O₃ sub-layer under Cr₂O₃; enhances oxidation resistance at 1000+℃ |
Si | 0.8-1.5 | Refines oxide film structure; improves adhesion of Cr₂O₃/Al₂O₃ to matrix |
C | 0.05-0.15 | Forms fine MC carbides (TiC/NbC); strengthens grain boundaries for creep resistance |
Mn | ≤1.0 | Reduces hot cracking during forging; refines grain size |
S/P | ≤0.015/≤0.02 | Ultra-low impurities prevent high-temp brittleness and oxide film spallation |
Ti/Nb | 0.1-0.5 (total) | Stabilizes carbides; inhibits intergranular corrosion |
Product Characteristics
1.Exceptional High-Temperature Oxidation Resistance: Cr-Al-Si synergy forms a dense, self-healing oxide film (Cr₂O₃ outer layer + Al₂O₃ inner layer) that resists scaling and spallation at 1100℃—oxidation rate ≤0.1 mm/year, outperforming most Ni-Fe-Cr alloys in long-term industrial furnace service;
2.Superior Anti-Carburization: High Cr content blocks carbon diffusion into the matrix, maintaining structural integrity in carburizing atmospheres (e.g., natural gas-fired furnaces) where other alloys suffer from carbide-induced brittleness;
3.Stable Mid-High Temp Creep Strength: Fine MC carbides (TiC/NbC) strengthen grain boundaries, delivering 800℃/10,000-hour creep rupture strength ≥120 MPa—suitable for load-bearing components like furnace radiant tubes;
4.Good Processability: Compatible with hot forging (1150-1200℃), rolling, and welding (TIG/MIG with matching Ni-Cr-Al-Si fillers); post-weld annealing (1050-1100℃) restores oxide film continuity and creep performance;
5.Broad Corrosion Adaptability: Resists not only oxidation/carburization but also molten salt (e.g., Na₂SO₄) corrosion and sulfur-containing atmospheres—ideal for multi-fuel industrial furnaces.
Metallographic Structure
At room temperature, Nicrofer 6025HT features a uniform face-centered cubic (FCC) austenitic matrix with ASTM grain size 5-8 grades. Dispersed within the matrix are fine, stable MC-type carbides (TiC/NbC, 100-300 nm) at grain boundaries and within grains—these carbides inhibit grain sliding under high temperatures, enhancing creep resistance. At 1000+℃, the austenitic structure remains stable with no brittle intermetallic phases (e.g., sigma, mu phase) formation. When exposed to high temperatures, the surface forms a 2-5 μm thick Cr₂O₃-Al₂O₃-SiO₂ composite oxide film that adheres tightly to the matrix, preventing further corrosion.
Product Forms and Executive Standards
Product Form | Main International Executive Standards | Application Reference |
Plates/Sheets | ASTM B572, EN 10088-2 | Industrial furnace liners, heat treatment furnace doors |
Seamless Pipes/Tubes | ASTM B622, EN 10216-5 | Furnace radiant tubes (gas/oil-fired), high-temp process pipelines |
Bars/Forgings | ASTM B574, EN 10269 | Heat treatment (e.g., annealing baskets, quenching racks), furnace fan blades |
Wires/Filler Metals | ASTM B755, EN 10250-3 | Welding filler wires for furnace components, high-temp spring wires |
Castings | ASTM B584, EN 10283 | Large furnace combustion chambers, molten salt bath containers |
