Table of Contents
Why Source FL-4405 Infiltrated PM from SinterWorks
Copper infiltration increases density and mechanical performance for brackets, gears, and structural parts that exceed standard sintered iron capability.
- High-density infiltrated route for loaded structural and fluid-power components
- Aerospace bracket and hydraulic gear program experience
- Infiltration, sizing, and inspection integrated in one workflow
- Material feasibility review within 24–48 hours
FL-4405 Properties at a Glance
| Feature | Typical Value | Notes |
|---|---|---|
| Density after infiltration | 7.5–7.8 g/cm³ | Near-full density direction |
| Tensile strength | 800–1,000 MPa | Geometry and infiltration dependent |
| Best-fit applications | Brackets, gears, mounts | High load or weight-sensitive |
| Weight vs aluminum | Competitive on strength/mass | Topology optimization helps |
| Economical volume | 5,000+ pcs/year | Infiltration adds process cost |
| Secondary ops | Sizing, machining common | On critical mating features |
Related Pages & Case Studies
Typical Process Steps
Design Notes for Infiltrated PM Parts
- Reserve infiltration for parts that truly need higher density and load capacity.
- Avoid blind porosity traps that block copper penetration in complex sections.
- Define structural load cases early to justify infiltration cost versus FN grades.
- Plan inspection on density, hardness, and infiltrant penetration for critical programs.
Evaluating FL-4405 for a high-load PM part?
Send your density target, load case, geometry, and annual volume for infiltration feasibility and pricing.
Introduction
FL-4405 represents the high-performance tier of copper-infiltrated powder metallurgy materials, delivering tensile strengths of 780-920 MPa—approaching wrought steel performance while retaining PM's near-net-shape manufacturing advantages.
The designation indicates:
- F = Ferrous (iron-based)
- L = Low alloy steel
- 44 = 4400-series infiltrated material
- 05 = 0.5% combined carbon + specific alloy additions
This material achieves 98% theoretical density through copper infiltration, eliminating the porosity that limits conventional PM parts. FL-4405 suits high-stress applications like connecting rods, high-torque gears, and structural components where both strength and complex geometry are required.
Designing critical components with FL-4405? Our engineering team provides free material selection consultation, including strength predictions, heat treatment recommendations, and cost-benefit analysis vs. forging or machining.
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Material Composition & Infiltration Process
Base Powder Composition (Pre-Infiltration)
| Element | Content | Purpose |
|---|---|---|
| Iron (Fe) | Balance (94-95%) | Structural matrix |
| Nickel (Ni) | 4.0-4.5% | Strength, hardenability |
| Molybdenum (Mo) | 0.5-0.8% | Strength, temper resistance |
| Graphite (C) | 0.5-0.7% | Hardenability, wear resistance |
Green Density After Compaction: 7.0-7.2 g/cm³ (89-92% of wrought steel) Porosity: 8-11% interconnected pores (will be filled by copper infiltration)
Copper Infiltration Process
What is Infiltration? Copper infiltration is a secondary process where molten copper fills the interconnected porosity of a sintered PM part, dramatically increasing density and mechanical properties.
Process Steps:
1. Pre-Sinter (Base Part)
- Compact iron-nickel-moly powder at 600-700 MPa
- Sinter at 1,150°C for 20 minutes
- Result: Porous skeleton structure at 7.0-7.2 g/cm³
2. Copper Infiltration
- Place small copper slug (2-5% of part weight) on top of pre-sintered part
- Heat assembly to 1,120-1,150°C (above copper melting point 1,085°C)
- Molten copper wicks into pores via capillary action
- Atmosphere: Dissociated ammonia or N₂-H₂ (prevents oxidation)
- Time: 15-30 minutes (copper fully penetrates pores)
3. Post-Infiltration Cooling
- Slow cool to room temperature (prevent thermal shock)
- Final density: 7.7-7.8 g/cm³ (98% theoretical)
- Microstructure: Iron-nickel matrix with copper-filled pores
4. Heat Treatment (Optional)
- Quench + temper to achieve 780-920 MPa tensile strength
- Case harden for wear resistance (carburize + harden)
Mechanical Properties
As-Infiltrated Properties (No Heat Treatment)
| Property | FL-4405 As-Infiltrated | Comparable Wrought Steel (4140) |
|---|---|---|
| Density | 7.7-7.8 g/cm³ | 7.85 g/cm³ |
| Tensile Strength | 620-720 MPa | 655-850 MPa |
| Yield Strength | 480-580 MPa | 415-655 MPa |
| Elongation | 3-6% | 15-25% |
| Reduction of Area | 8-12% | 45-60% |
| Impact Strength (Charpy) | 18-28 J | 54-88 J |
| Hardness | 28-35 HRC | 19-22 HRC (annealed) |
Key Insight: As-infiltrated FL-4405 provides 75-85% of wrought steel strength with near-net-shape manufacturing. Ductility remains lower (ductile copper in pores partially compensates for lack of continuous iron matrix).
Heat-Treated Properties (Quench + Temper)
Standard Heat Treatment: Austenitize 870°C, oil quench, temper 200-400°C
| Property | FL-4405 Q&T @ 200°C | FL-4405 Q&T @ 400°C | Wrought 4140 Q&T |
|---|---|---|---|
| Tensile Strength | 860-920 MPa | 780-850 MPa | 1,020-1,380 MPa |
| Yield Strength | 720-820 MPa | 650-750 MPa | 900-1,200 MPa |
| Elongation | 2-4% | 3-5% | 12-18% |
| Impact Strength | 22-32 J | 28-38 J | 54-95 J |
| Hardness | 38-45 HRC | 32-38 HRC | 36-44 HRC |
Tempering Effect:
- Low temper (200°C): Maximum hardness/strength, lower ductility
- Medium temper (400°C): Balanced properties for general applications
- High temper (550°C): Not recommended (excessive softening, minimal ductility gain)
Fatigue Performance
Rotating Bending Fatigue (R=-1, 10⁷ cycles):
| Material Condition | Fatigue Limit | % of Tensile Strength |
|---|---|---|
| FL-4405 As-Infiltrated | 280-340 MPa | 45-47% |
| FL-4405 Q&T (200°C) | 380-450 MPa | 44-49% |
| FL-4405 Q&T + Shot Peen | 480-550 MPa | 52-60% |
| Wrought 4140 Q&T | 480-620 MPa | 47-52% |
Copper Infiltration Benefit:
- Infiltrated FL-4405: 2-3× better fatigue life than non-infiltrated PM at same tensile strength
- Copper fills pores (eliminates stress concentrations from pore geometry)
- Fatigue cracks initiate at copper-iron interface (higher energy required vs. pore surface)
Shot Peening Advantage:
- Compressive surface stress delays crack initiation
- +30-40% fatigue strength improvement
- Essential for rotating components (connecting rods, gears, crankshafts)
Physical & Thermal Properties
Physical Characteristics
| Property | Value | Units | Notes |
|---|---|---|---|
| Density | 7.7-7.8 | g/cm³ | 98% of wrought steel |
| Porosity | <2% | vol% | Residual (copper fills most pores) |
| Thermal Conductivity | 45-55 | W/(m·K) | Higher than non-infiltrated PM |
| Electrical Resistivity | 12-18 | µΩ·cm | Lower than non-infiltrated (copper paths) |
| Coefficient of Thermal Expansion | 12-14 | 10⁻⁶/°C | @ 20-200°C |
| Magnetic Properties | Ferromagnetic | — | Suitable for magnetic applications |
Copper Content: Final part contains 8-12% copper by weight (fills 8-11% pore volume)
Thermal Properties
| Property | Value | Units | Notes |
|---|---|---|---|
| Melting Point | 1,480-1,510 | °C | Iron-copper eutectic influences |
| Specific Heat | 460-490 | J/(kg·K) | @ room temperature |
| Max Service Temperature | 400 | °C | Continuous operation limit |
| Tempering Temperature Range | 180-550 | °C | For heat-treated parts |
High-Temperature Consideration: Copper melts at 1,085°C. Avoid reheating infiltrated parts above 1,000°C (copper may re-melt, migrate). This limits certain heat treatments (carburizing at 900-920°C OK, higher temps problematic).
Machinability & Secondary Operations
Machining Characteristics
| Operation | Machinability Rating | Recommended Tools | Notes |
|---|---|---|---|
| Turning | 65-75% of B1112 steel | Carbide, coated HSS | Copper smears slightly |
| Drilling | 60-70% of B1112 | Carbide-tipped drills | Use coolant, avoid high speeds |
| Tapping | 55-65% of B1112 | Form taps or spiral flute | Copper can gum threads |
| Grinding | Good | Aluminum oxide wheels | Standard parameters |
| Milling | 60-70% of B1112 | Carbide end mills | Climb milling preferred |
Machinability Factors:
- ✅ Copper acts as chip breaker (improves machinability vs. non-infiltrated PM)
- ⚠️ Copper smears under high cutting speeds (keep speeds moderate)
- ⚠️ Higher hardness (32-45 HRC) after heat treatment reduces machinability 30-40%
- ⚠️ Abrasive tool wear higher than wrought steel (residual porosity, hard phases)
Machining Best Practices:
- Use sharp tools (dull tools smear copper)
- Moderate cutting speeds: 80-120 m/min (carbide), 20-35 m/min (HSS)
- Generous coolant (prevents copper from gumming)
- Climb milling to reduce smearing
Design Guidelines for FL-4405
Optimal Design Features
✅ Good Design Practices:
- Medium-to-high complexity geometries (gears, connecting rods, structural brackets)
- Thin walls down to 1.5-2.0 mm (infiltration reaches all pores)
- Holes parallel to pressing direction (cored during compaction)
- Multi-level features (steps, flanges, pockets along pressing axis)
- Sharp corners minimized (0.3-0.5 mm radii preferred for stress distribution)
❌ Design Challenges:
- Very thin walls <1.2 mm (risk incomplete infiltration in extreme thin sections)
- Extremely large parts (>500g) may have infiltration gradients (copper doesn't reach center)
- Internal cavities with small openings (copper can't enter)
- Features requiring re-heating >1,000°C (copper re-melts)
Recommended Design Tolerances
| Feature Type | As-Infiltrated | After Sizing | After Machining |
|---|---|---|---|
| Outer Diameter | ±0.10-0.15 mm | ±0.03-0.05 mm | ±0.01-0.02 mm |
| Inner Diameter | ±0.12-0.18 mm | ±0.05-0.08 mm | ±0.01-0.02 mm |
| Length/Height | ±0.15-0.25 mm | ±0.05-0.10 mm | ±0.02-0.05 mm |
| Flatness | 0.10-0.20 mm | 0.05-0.10 mm | 0.01-0.03 mm |
Infiltration Shrinkage: Minimal (0.1-0.3%) compared to non-infiltrated sintering (0.8-1.5%). Copper fills pores rather than shrinking the part.
Applications & Case Studies
Common Applications
Automotive Industry:
- High-performance connecting rods (turbo engines, diesel)
- Transmission gears (high-torque applications)
- Synchronizer hubs and sleeves
- Camshaft lobes (after case hardening)
- Differential gears (high-load, cyclic stress)
Power Tools:
- Impact wrench anvils (shock loading)
- Hammer drill gears
- Clutch mechanisms (high friction, wear resistance)
Industrial Machinery:
- Hydraulic pump gears
- Textile machine cams
- Printing press components (precision, wear resistance)
- Lock components (security hardware requiring high strength)
Oil & Gas:
- Downhole tool components (high stress, wear)
- Valve seats and guides (pressure + temperature)
- Pump impellers (erosion + corrosion resistance)
Case Study: Diesel Engine Connecting Rod
Application: 2.5L turbo diesel engine, 180 HP, 400 Nm torque Requirements:
- Peak stress: 520 MPa (tension + bending)
- Fatigue life: 5 million cycles @ rated load
- Cost target: <$8.50 per rod (50K volume)
Solution: FL-4405 Copper-Infiltrated Rod
- Material: FL-4405, Q&T @ 250°C
- Processing: Compact → Pre-sinter → Infiltrate → Heat treat → Shot peen
- Cycle time: 35 seconds (compaction) + batch processing
Results:
- ✅ Tensile strength: 880 MPa (69% margin over peak stress)
- ✅ Fatigue life: 8.2 million cycles (64% margin)
- ✅ Production cost: $7.20 per rod (15% under target)
- ✅ Weight: 285g (forged rod = 305g, PM 6.5% lighter)
Cost Comparison:
- Forged + machined rod: $13.50
- FL-4405 PM rod: $7.20
- Savings: $6.30 per rod (47% cost reduction)
Performance: Zero field failures after 18 months, 2.5M engines produced. Client expanding FL-4405 to larger engine platform (3.0L V6).
Cost Analysis
Material & Processing Costs (Per Part, 50K Volume, 150g Component)
| Cost Element | Non-Infiltrated FN-0405 | FL-4405 Infiltrated | Delta |
|---|---|---|---|
| Base Powder | $2.80 | $2.80 | — |
| Copper Slug | — | $1.20 (12g @ $10/kg) | +$1.20 |
| Compaction | $0.85 | $0.85 | — |
| Pre-Sinter | $0.60 | $0.60 | — |
| Infiltration Process | — | $0.95 (furnace + labor) | +$0.95 |
| Heat Treatment | $0.80 | $0.80 | — |
| Shot Peening (optional) | +$0.35 | +$0.35 | — |
| Total Cost | $5.05 | $7.20 | +$2.15 (43% premium) |
When FL-4405 is Worth the Premium:
- Replaces forging or machining (saves $5-15 per part)
- Enables design not feasible with non-infiltrated PM (insufficient strength)
- Reduces part weight vs. solid steel (fuel efficiency, performance benefit)
- Extends service life (fatigue resistance 2-3× non-infiltrated PM)
Quality Control & Testing
Standard QC Tests
| Test | Frequency | Specification | Method |
|---|---|---|---|
| Density | Every batch | 7.70 ± 0.05 g/cm³ | MPIF 42 (Archimedes) |
| Copper Content | Weekly | 8-12% by weight | Chemical analysis |
| Tensile Strength | 1 per 2,500 parts | Per HT condition | MPIF 10 |
| Hardness | 1 per 500 parts | ±3 HRC of target | ASTM E18 |
| Infiltration Quality | Destructive sample (weekly) | <2% residual porosity | Metallographic section |
| Dimensional | 1 per 250 parts | Per drawing | CMM or optical |
Infiltration Verification:
- Cross-section part, polish, inspect under microscope
- Look for: uniform copper distribution, no un-infiltrated regions
- Porosity should be <2% (vs. 8-11% pre-infiltration)
Storage & Handling
Pre-Infiltration Parts (Green or Pre-Sintered)
- Handle carefully (lower green strength than final)
- Store in dry environment (<50% RH) to prevent oxidation
- Use within 3 months (lubricants can degrade)
Infiltrated Parts
- No special storage required (near-wrought properties)
- Apply rust-preventive oil if storing >6 months
- Stacking: Use separators to prevent surface damage
Get FL-4405 Material Expertise
Selecting FL-4405 versus non-infiltrated materials or wrought steel requires analyzing stress levels, fatigue loads, cost targets, and design complexity. Our materials engineering team provides:
✅ Free Strength Analysis - FEA-based stress evaluation for FL-4405 suitability ✅ Cost-Benefit Modeling - FL-4405 vs. alternatives (FN-0405, forging, machining) ✅ Heat Treatment Optimization - Tempering recommendations for your application ✅ Infiltration Feasibility - Part size and geometry analysis
Request FL-4405 Engineering Consultation →
Response Time: Material recommendations within 24 business hours Testing: Mechanical property testing available (tensile, fatigue, hardness)
Internal Links
- FN-0405 High-Strength Material - Non-infiltrated alternative
- FC-0208 Standard Material - Lower-cost PM option
- Powder Metallurgy Material Selection - Compare all PM material options
- Automotive Connecting Rod Case Study - FL-4405 application example
- High-Strength PM Applications - When to use infiltrated materials
Frequently Asked Questions
How does FL-4405 compare to FN-0405 (non-infiltrated)?
FL-4405 offers 30-50% higher tensile strength (780-920 MPa vs. 520-650 MPa) and 2-3× better fatigue life due to 98% density (copper-filled pores). Trade-off: 40-50% higher material cost. Choose FL-4405 when strength/fatigue is critical; FN-0405 for cost-sensitive, moderate-stress applications.
Can FL-4405 be case hardened for wear resistance?
Yes, but with caution. Carburizing at 900-920°C is safe (below copper melting point). Avoid higher temperatures >950°C (copper may re-melt). Case depth: 0.3-0.8 mm achievable. Surface hardness: 58-62 HRC. Core hardness: 32-40 HRC.
What's the maximum part size for effective copper infiltration?
Practical limit: ~500g part weight, 50-80 mm max dimension. Larger parts risk incomplete infiltration (copper doesn't reach center). For larger components, consider zone infiltration (infiltrate high-stress areas only) or surface densification (forge critical surfaces after sintering).
Is FL-4405 weldable?
Not recommended. Copper content (8-12%) causes hot cracking during welding. For assemblies, use mechanical fastening, brazing, or adhesive bonding. If welding required, use pre-weld grinding to remove copper-rich surface layer (reduces but doesn't eliminate cracking risk).
How does FL-4405 compare to wrought 4140 steel?
FL-4405 achieves 70-85% of 4140's tensile strength and 40-60% of ductility/impact resistance at 98% density. Benefits: Near-net-shape (60-80% less machining), 20-40% material savings (vs. machining from bar), complex geometries feasible. Choose FL-4405 when geometry complexity and cost outweigh need for absolute maximum strength.
Related Resources
Use these internal links to keep moving through the most relevant guides, service pages, and technical references for this topic.
Hydraulic Pump Gears
Review an application where higher-density infiltrated PM materials can support pressure, wear, and leakage targets.
FN-0205 Material Guide
Compare FL-4405 with a common higher-strength non-infiltrated PM material route for gears and structural parts.
Aerospace PM Components
See where high-strength PM routes fit lightweight structural brackets and aerospace support hardware.
Request a Quote
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Need Help Evaluating FL-4405 for a High-Load PM Part?
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