1.4913, X19CrMoNbVN11-1, 403Cb+
Turbine blade steels such as 1.4913 (X19CrMoNbVN11-1), 403Cb+, and their related alloys represent a critical class of materials designed for high-temperature service in steam and gas turbines. These martensitic stainless steels combine excellent creep resistance, good mechanical properties at elevated temperatures, and corrosion resistance - making them ideal for compressor blades, turbine blades, and other critical rotating components.
Table of Contents
What is 1.4913, X19CrMoNbVN11-1, 403Cb+?
The 1.4913/X19CrMoNbVN11-1/403Cb+ family of alloys represents an optimized balance of properties for critical turbine applications. Their carefully controlled chemistry and processing requirements ensure reliable performance in demanding high-temperature environments. The GE B50A365 specification in particular demonstrates the rigorous quality standards needed for power generation components, with comprehensive requirements covering chemistry, heat treatment, mechanical properties, and quality assurance.
For engineers selecting materials for turbine blades or other high-temperature components, these alloys offer an excellent combination of strength, creep resistance, and corrosion resistance - particularly in the 500-650°C service range. Their proven performance in power generation applications makes them a preferred choice when reliability and long service life are paramount.
This comprehensive guide provides metallurgical professionals, engineers, and researchers with detailed technical data on these important materials, including:
- Material specifications and international designations
- Chemical composition comparisons
- Mechanical properties across temperature ranges
- Heat treatment requirements
- High-temperature performance characteristics
- Processing and fabrication considerations
Material Specifications and Designations
These chromium-niobium alloy steels are known under various designations in different standards:
| Material Number | EN/DIN | AFNOR | GOST | ISO | GE Specification | UNS |
|---|---|---|---|---|---|---|
| 1.4913 | X19CrMoNbVN11-1 | NF Z20CDNbV11 | 18Ch11MNFB (18Х11МНФБ) | - | - | - |
| 1.4916 | - | NF Z21CDNbV11 | 2Х11МФБН, ЕП291 | ISO X18CrMnMoNbVN12 | - | - |
| - | - | 56T5 | - | - | B50A365 (403Cb+) | - |
The GE specification B50A365 (403Cb+) represents General Electric's proprietary version of this alloy class with particularly stringent requirements for turbine applications.
Applications
Applications
These alloys are specifically designed for:
-
Steam Turbine Components:
- High-pressure blades
- Rotor blades
- Buckets
- Partitions
-
Gas Turbine Components:
- Compressor blades
- Variable inlet guide vanes
- Rotor disks
-
Other High-Temperature Applications:
- Fasteners
- Valve components
- High-pressure piping
Chemical Composition (%)
| Grade | Chemical Composition % | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| C | Mn | Si | P | S | Cr | Ni | Mo | V | Nb | Al | W | B | N | Cu | Ti | ||
EN 1.4913, X19CrMoNbVN11-1 |
0.17 - 0.23 | 0.4 - 0.9 | Max 0.5 | Max 0.025 | Max 0.015 | 10.0 - 11.5 | 0.2 - 0.6 | 0.5 - 0.8 | 0.1 - 0.3 | 0.25 - 0.55 | Max 0.02 | Max 0.7 | 0.005 - 0.015 | 0.05 - 0.10 | - | - | |
NF Z20CDNbV11, 56T5 |
0.18 - 0.25 | 0.3 - 0.8 | 0.1 - 0.5 | Max 0.025 | Max 0.015 | 10.0 - 12.0 | Max 1.0 | 0.5 - 1.0 | 0.1 - 0.3 | 0.25 - 0.55 | - | - | - | 0.05 - 0.10 | - | - | |
NF Z21CDNbV11 |
0.16 - 0.25 | 0.3 - 0.8 | 0.1 - 0.5 | Max 0.030 | Max 0.015 | 10.0 - 12.0 | Max 1.0 | 0.5 - 1.0 | 0.1 - 0.3 | 0.25 - 0.55 | - | - | - | 0.05 - 0.10 | - | - | |
X18CrMnMoNbVN12, 1.4916 |
0.15 - 0.20 | 0.5 - 1.0 | Max 0.5 | Max 0.040 | Max 0.030 | 10.0 - 13.0 | Max 0.6 | 0.3 - 0.9 | 0.1 - 0.4 | 0.2 - 0.6 | - | - | - | 0.05 - 0.10 | - | - | |
18Ch11MNFB, 18Х11МНФБ, 2Х11МФБН, ЕП291 |
0.15 - 0.21 | 0.6 - 1.0 | Max 0.6 | Max 0.030 | Max 0.025 | 10.0 - 11.5 | 0.5 - 1.0 | 0.8 - 1.1 | 0.2 - 0.4 | 0.20 - 0.45 | - | Max 0.2 | - | - | |||
B50A365 403Cb+ |
0.15-0.20 | 0.20-0.60 | 0.50-0.80 | ≤0.020;≤0.025 | ≤0.010;≤0.025 | 10.0-11.0 | 0.80-1.10 | 0.35-0.55 | 0.15-0.25 | 0.20 - 0.45 | 0.04-0.08 | 0.30-0.60 | - | - | |||
Key features of the chemistry:
- Chromium provides oxidation resistance and solid solution strengthening
- Molybdenum enhances high-temperature strength
- Niobium (columbium) forms stable carbides for creep resistance
- Vanadium contributes to precipitation hardening
- Nitrogen strengthens the matrix and stabilizes austenite during heat treatment
Material Properties
Room Temperature Properties
| Property | 403Cb+ (B50A365) | 1.4913 | NF Z20CDNbV11 | Test Standard |
|---|---|---|---|---|
| Tensile Strength (min) | 140 ksi (965 MPa) | 900-1100 MPa | 900-1100 MPa | ASTM A370 |
| Yield Strength (0.2% offset, min) | 100 ksi (690 MPa) | 700 MPa | 700 MPa | ASTM A370 |
| Elongation (min) | 15% | 15% | 15% | ASTM A370 |
| Reduction of Area (min) | 45% | 50% | 50% | ASTM A370 |
| Hardness (Brinell) | 285-321 HB | 270-330 HB | 270-330 HB | ASTM E10 |
| Charpy Impact (min) | 8 ft-lbs (11 J) | 30 J | 30 J | ASTM E23 |
High Temperature Mechanical Properties
These alloys maintain excellent strength at elevated temperatures:
| Temperature | 0.2% Proof Stress (MPa) | Tensile Strength (MPa) |
|---|---|---|
| 400°C | 550 | 700 |
| 500°C | 500 | 650 |
| 600°C | 400 | 550 |
Creep and Stress Rupture Properties
The 403Cb+ specification requires:
- Stress rupture testing at 650°C (1200°F) with minimum 33 ksi (228 MPa) stress
- Minimum time to rupture of 25 hours
- Combination smooth and notched specimen testing
Typical stress rupture performance:
- 100,000 hours rupture strength at 600°C: ~120 MPa
- 100,000 hours rupture strength at 650°C: ~80 MPa
Grain Size Requirements
- Average prior austenitic grain size of ASTM No. 4 or finer
- Maximum individual grain size of ASTM No. 2
- Maximum 1% delta ferrite
Physical Properties
| Property | Value |
|---|---|
| Density | 7.8 g/cm³ |
| Melting Range | 1420-1460°C |
| Thermal Conductivity (20°C) | 28 W/m·K |
| Specific Heat (20°C) | 460 J/kg·K |
| Electrical Resistivity | 0.75 μΩ·m |
| Coefficient of Thermal Expansion (20-600°C) | 12.5 × 10⁻⁶/K |
| Elastic Modulus | 210 GPa |
| Poisson's Ratio | 0.29 |
Heat Treatment
The heat treatment of these alloys is critical for achieving optimal properties. The B50A365 specification provides detailed requirements:
For Final Properties (Classes A, B & C)
- Austenitizing: 2000-2050°F (1093-1121°C), hold for uniform temperature
- Quenching: In oil or rapidly moving air below Mf temperature
- Tempering: Minimum 1185°F (640°C) to achieve required properties
For Annealed Condition (Classes A1 & B1)
- Maximum hardness of 302 HB
- Capable of subsequent heat treatment to final properties
Special Considerations for Class B (Straightened Material)
- Additional heat treatment cycle after straightening:
- Austenitize → Quench → Temper at 615°C → Straighten → Final temper ≥640°C
- Straightening after final temper prohibited without approval
Processing Performance
Forging
- Recommended forging temperature range: 1050-850°C
- Requires controlled cooling after forging to prevent cracking
- Forging reduction ratio should be ≥3:1 for optimal properties
Machining
- Best machined in annealed condition
- Use positive rake tools with carbide inserts
- Recommend cutting speeds of 30-50 m/min for turning
- Requires rigid setups due to material toughness
Welding
- Weldable using matching composition filler metals
- Preheat to 250-350°C recommended
- Post-weld heat treatment required (typically 700-750°C)
- Susceptible to HAZ cracking if procedures not followed
Non-Destructive Testing
- Ultrasonic testing per P3C-AL-0013 for forgings
- Magnetic particle inspection per P3C-AL-0003
- Liquid penetrant examination for surface defects
Quality Assurance Requirements
The B50A365 specification includes stringent QA provisions:
Chemical Analysis:
- Class A/A1: Master heat analysis
- Class B/B1/C: Every remelted ingot analysis
Mechanical Testing:
- Hardness testing for all classes
- Tensile testing (location and orientation specified)
- Stress rupture testing for heat-treated material
- Charpy impact for forgings
Metallographic Examination:
- Grain size measurement (ASTM E112)
- Delta ferrite content
- Cleanliness rating (ASTM E45)
Comparative Analysis with Similar Alloys
While 403Cb+ and related alloys share many characteristics with conventional 12%Cr steels, key differences include:
Superior to 410 stainless steel in:
- Creep resistance
- Toughness
- High-temperature strength
Compared to 17-4PH:
- Better thermal stability
- Higher creep strength
- More suitable for rotating components
Advantages over cobalt-based alloys:
- Lower cost
- Better fabricability
- Adequate for many intermediate temperature applications