Nimonic 115
Introduction to Nimonic 115
Nimonic 115 is a high-strength, nickel-chromium-cobalt superalloy developed for extreme temperature applications, particularly in the aerospace and power generation sectors. Designed to maintain structural integrity up to 1050°C, this alloy is characterized by its high gamma prime (γ′) content and excellent creep resistance. It is extensively used for turbine blades, nozzle guide vanes, and disc components where long-term thermal and mechanical loading is critical.
Due to its demanding applications, Nimonic 115 components are typically produced via CNC machining services to ensure tight tolerances and repeatability. CNC machining allows for precision shaping of complex geometries in this hard-to-machine material, providing the dimensional control required for performance-critical assemblies.
Chemical, Physical, and Mechanical Properties of Nimonic 115
Nimonic 115 (UNS N19115 / W.Nr. 2.4639) is a precipitation-hardened, vacuum-cast superalloy developed for long-term strength and oxidation resistance under continuous service in high-heat environments.
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (≥50.0) | Matrix stability and corrosion resistance |
Chromium (Cr) | 14.0–16.0 | Enhances oxidation and corrosion resistance |
Cobalt (Co) | 14.0–16.0 | Increases strength and thermal fatigue resistance |
Molybdenum (Mo) | 3.0–5.0 | Creep strengthening through solid solution hardening |
Aluminum (Al) | 5.0–6.0 | Forms Ni₃Al γ′ phase to enhance high-temperature strength |
Titanium (Ti) | 1.0–2.0 | Contributes to γ′ phase formation for precipitation hardening |
Carbon (C) | ≤0.15 | Carbide precipitation improves creep and rupture strength |
Boron (B) | ≤0.015 | Grain boundary strengthening |
Zirconium (Zr) | ≤0.15 | Increases creep rupture life |
Iron (Fe) | ≤1.0 | Residual element |
Manganese (Mn) | ≤1.0 | Improves hot workability |
Silicon (Si) | ≤1.0 | Oxidation aid |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 8.40 g/cm³ | ASTM B311 |
Melting Range | 1335–1385°C | ASTM E1268 |
Thermal Conductivity | 11.5 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.12 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 13.3 µm/m·°C (20–1000°C) | ASTM E228 |
Specific Heat Capacity | 440 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 210 GPa at 20°C | ASTM E111 |
Mechanical Properties (Solution Treated + Aged)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 1180–1350 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 880–960 MPa | ASTM E8/E8M |
Elongation | ≥15% | ASTM E8/E8M |
Hardness | 280–310 HB | ASTM E10 |
Creep Rupture Strength | 240 MPa at 950°C (1000h) | ASTM E139 |
Fatigue Resistance | Excellent | ASTM E466 |
Key Characteristics of Nimonic 115
High Strength at Extreme Temperatures Delivers tensile strength above 1180 MPa and yield strength over 880 MPa at temperatures reaching 950°C.
Gamma Prime Reinforcement High γ′ phase volume fraction provides excellent strength retention and resistance to thermal degradation over time.
Superior Oxidation Resistance Chromium and aluminum additions form a stable oxide layer that prevents surface degradation up to 1050°C.
Creep and Fatigue Performance Creep rupture strength of 240 MPa at 950°C for 1000 hours ensures long-life reliability in rotating turbine parts.
Dimensional Stability Under Thermal Cycling With a thermal expansion coefficient of 13.3 µm/m·°C, it resists warping and deformation in cyclic heat environments.
CNC Machining Challenges and Solutions for Nimonic 115
Machining Challenges
Rapid Tool Degradation
The combination of high hardness and γ′ phase particles leads to fast wear of conventional tools.
Low Thermal Conductivity
Traps heat in the cutting zone, increasing tool edge temperature and risk of dimensional inaccuracy.
Work Hardening
Requires consistent engagement and sharp tooling to prevent build-up of hardened layers.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | Carbide (K30), ceramic inserts for finishing | Maintains hardness at high temps |
Coating | AlCrN or TiSiN PVD (3–5 µm) | Heat protection and wear reduction |
Geometry | Positive rake (6–10°), honed cutting edge (~0.05 mm) | Controls forces and surface finish |
Cutting Parameters (ISO 3685 Compliant)
Operation | Speed (m/min) | Feed (mm/rev) | Depth of Cut (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 10–15 | 0.15–0.25 | 1.5–2.5 | 100–120 |
Finishing | 25–35 | 0.05–0.10 | 0.3–0.8 | 120–150 |
Surface Treatment for Machined Nimonic 115 Parts
Hot Isostatic Pressing (HIP)
HIP reduces internal porosity and increases fatigue strength by more than 25%, particularly for rotating components.
Heat Treatment
Heat Treatment includes solution annealing (~1145°C) followed by controlled aging to maximize γ′ precipitation for optimal strength.
Superalloy Welding
Superalloy Welding with ERNiCrCoMo alloy fillers ensures crack-free joints, maintaining ≥90% of base metal mechanical properties.
Thermal Barrier Coating (TBC)
TBC Coating reduces substrate temperature by up to 200°C in turbine vanes and blades.
Electrical Discharge Machining (EDM)
EDM is used to create tight-tolerance cooling holes with ±0.005 mm accuracy and no thermal stress impact.
Deep Hole Drilling
Deep Hole Drilling achieves Ra <1.6 µm surface finish and concentricity within 0.3 mm/m for L/D >30:1 parts.
Material Testing and Analysis
Material Testing includes creep, tensile, XRD, SEM, and ultrasonic inspection to ASME and ASTM standards.
Industry Applications of Nimonic 115 Components
Aerospace Turbine Engines: Turbine blades, discs, and combustion hardware exposed to extreme heat.
Power Generation: High-temperature steam turbine vanes and fasteners.
Nuclear Systems: Components exposed to both thermal stress and radiation.
Automotive Racing Engines: Exhaust valves, turbocharger wheels, and valve guides.
Industrial Gas Turbines: Rotors and guide vanes in heat-cycling combustion zones.
FAQs
What tool materials and coatings are optimal for CNC machining of Nimonic 115?
How can dimensional stability be maintained in complex Nimonic 115 parts exposed to thermal cycling?
What surface treatments enhance fatigue and oxidation resistance for machined Nimonic 115 components?
How does Nimonic 115 compare to other nickel alloys in CNC machining performance and lifespan?
What is the recommended post-machining testing for aerospace-grade Nimonic 115 parts?
Explore Related Blogs
