Food Machinery 316L PM Components - Application Example

Application Background

Equipment Type

Food packaging machinery for dairy and beverage applications

Component Requirements

• Corrosion resistance in wet, cleaning chemical environment
• Smooth surface finish for sanitation
• Dimensional consistency for assembly
• Cost-effective manufacturing for production volumes

Original Design Approach

Mixed approach using:

• Machined 316L stainless steel components (higher cost)
• Zinc-plated carbon steel components (corrosion concerns)

Material Selection: 316L Stainless Steel

Why 316L Was Selected

Corrosion Resistance:

• 316L provides good resistance to many cleaning chemicals
• Molybdenum content (2-3%) enhances chloride resistance
• Suitable for wet food processing environments

Food Contact Considerations:

• 316L is commonly used in food processing equipment
• Low carbon content (<0.03%) reduces carbide precipitation
• Non-magnetic characteristic

Manufacturing Benefits:

• PM route enables near-net-shape components
• Reduces machining compared to bar stock starting material
• Good for medium to high production volumes

Important Note: Use of materials in food contact applications requires verification of suitability for specific conditions and compliance with applicable regulations. Material selection alone does not ensure compliance.

PM Manufacturing Process

Process Steps

1. High-Density Compaction
   • Compaction pressure: 700 MPa target
   • Green density: ~7.2 g/cm3
2. High-Temperature Sintering
   • Sintering temperature: 1280 deg C
   • Atmosphere: High-purity hydrogen (dew point <-40 deg C)
   • Purpose: Achieve high density and corrosion resistance
3. Passivation Treatment
   • Chemical treatment per ASTM A967
   • Purpose: Promote protective chromium oxide film formation
4. Electropolishing
   • Metal removal: 20-30 um
   • Target surface finish: Ra <0.4 um
   • Purpose: Smooth surface, improved cleanability

Design Optimizations

• Wall thickness: 4-6mm (suitable for PM processing)
• Corner radii: R2mm minimum (facilitate cleaning)
• Drainage features: Prevent liquid accumulation

Performance Characteristics

Material Properties Achieved

Corrosion Resistance

• Tested in 5% acetic acid solution at 80 deg C
• No visible pitting or discoloration after 500 hours
• Passivation layer intact

Note: Actual corrosion performance depends on specific environment, cleaning chemicals, and maintenance practices.

Cost Comparison

Example Component: Guide Rail

Machined 316L Approach:

• Material cost: Higher (bar stock)
• Machining time: Extensive
• Total estimated cost: Baseline

PM 316L Approach:

• Material cost: Lower (near-net-shape)
• Secondary operations: Minimal machining, plus electropolishing
• Total estimated cost: Approximately 30-40% reduction vs machined

Zinc-Plated Carbon Steel:

• Initial cost: Lowest
• Long-term performance: Coating degradation observed
• Replacement frequency: Higher

Cost Note: Actual costs vary based on production volume, complexity, and specific supplier pricing. Figures shown are illustrative of potential savings, not guaranteed results.

Application-Specific Results

Performance in Service

Corrosion Resistance:

• No corrosion failures observed in 18-month evaluation period
• Compared to baseline zinc-plated parts which showed coating degradation

Surface Cleanability:

• Electropolished surface facilitated cleaning
• Smooth finish reduced cleaning time in customer trials

Dimensional Consistency:

• PM process provided consistent part dimensions
• Reduced assembly variation compared to machined parts with wider tolerances

Quality Observations

• Surface finish: Ra 0.35 um average (target <0.8 um)
• Dimensional capability: Cpk 1.8 achieved
• Visual inspection: Zero surface defects in production sampling

Important: These results are specific to this application example and processing conditions. Performance in different applications may vary.

Key Learnings

Material Selection

1. 316L suitability for food processing environments depends on specific chemicals, concentration, and exposure time
2. Surface finish is critical for cleanability - electropolishing significantly improves baseline PM surface
3. High-purity sintering atmosphere essential for stainless steel corrosion resistance

Processing Considerations

1. Sintering atmosphere quality directly affects corrosion performance
2. Passivation treatment helps establish protective oxide layer
3. Electropolishing both improves surface finish and removes any surface contamination

Cost-Performance Balance

1. PM approach provided cost reduction while meeting performance requirements
2. Initial tooling investment amortized across production volume
3. Reduced secondary machining offset electropolishing cost addition

Technical Specifications

Material: 316L Stainless Steel PM

• Composition: 16-18% Cr, 10-14% Ni, 2-3% Mo, <0.03% C
• Density: 7.4-7.6 g/cm3 (96-98% theoretical)
• Hardness: 75-85 HRB

Surface Treatment

• As-Sintered: Ra 1.2-1.8 um typical
• After Electropolishing: Ra 0.3-0.4 um achieved
• Treatment: Passivation per ASTM A967

Design Guidelines

For Food Processing Equipment Applications

Material Considerations:

• 316L offers good corrosion resistance for many food environments
• Material suitability should be verified for specific application conditions
• Consider environmental factors: cleaning chemicals, temperature, exposure time

Surface Finish:

• Electropolishing recommended for food contact surfaces
• Target Ra <0.8 um for improved cleanability
• Smooth surfaces reduce bacterial adhesion potential

Design Features:

• Minimize crevices and dead zones
• Include drainage to prevent liquid accumulation
• Design for disassembly and cleaning access

Quality Requirements:

• Source material from qualified suppliers
• Implement appropriate quality controls
• Maintain traceability documentation

Regulatory Considerations

Important Notes:

1. Material use in food contact applications requires verification of suitability for specific conditions
2. Compliance with applicable regulations and standards is the responsibility of the equipment manufacturer
3. Material properties alone do not constitute regulatory approval
4. Specific testing and documentation requirements vary by region and application
5. Consult with regulatory specialists for specific application requirements

Get 316L PM Components for Industrial Applications

SinterWorks manufactures 316L stainless steel PM components:

• High-purity hydrogen sintering capability
• Electropolishing services available
• Design for manufacturing consultation
• Production volumes from 10,000 to 500,000+ parts/year

Note: Food contact applications require additional considerations beyond general manufacturing. Consult regulatory and food safety specialists for specific requirements.

Contact us to discuss your stainless steel component requirements.