ISO 18203:2016 Calculator
Steel — Determination of the thickness of surface-hardened layers
Case Hardening Depth (CHD)
CHD Measurement Points
CHD = d₁ + (d₂ – d₁) × (H₁ – Limit) / (H₁ – H₂)
CHD Calculator
CHD Calculation Result
Enter values and click Calculate
Formula: CHD = d₁ + (d₂ – d₁) × (H₁ – limit)/(H₁ – H₂)
Example Calculation
Given:
• d₁ = 0.5 mm, H₁ = 600 HV
• d₂ = 0.8 mm, H₂ = 500 HV
• Limit = 550 HV
Check conditions:
• d₂ – d₁ = 0.8 – 0.5 = 0.3 mm ≤ 0.3 mm ✓
• H₁ > H₂: 600 > 500 ✓
Calculate:
CHD = 0.5 + (0.8 – 0.5) × (600 – 550) / (600 – 500)
CHD = 0.5 + 0.3 × 50 / 100
CHD = 0.5 + 0.15 = 0.65 mm
• d₁ = 0.5 mm, H₁ = 600 HV
• d₂ = 0.8 mm, H₂ = 500 HV
• Limit = 550 HV
Check conditions:
• d₂ – d₁ = 0.8 – 0.5 = 0.3 mm ≤ 0.3 mm ✓
• H₁ > H₂: 600 > 500 ✓
Calculate:
CHD = 0.5 + (0.8 – 0.5) × (600 – 550) / (600 – 500)
CHD = 0.5 + 0.3 × 50 / 100
CHD = 0.5 + 0.15 = 0.65 mm
Requirements: d₂ – d₁ ≤ 0.3 mm, H₁ > H₂, minimum 5 measurements per distance
Surface Hardening Depth (SHD)
SHD Measurement Concept
Hardness Limit = A × Minimum Surface Hardness
SHD Calculator
SHD Calculation Result
Enter values and click Calculate
Formula: Hardness Limit = A × Minimum Surface Hardness
Example Calculation
Given:
• Minimum Surface Hardness = 450 HV
• Factor A = 0.80 (standard)
Calculate:
Hardness Limit = 0.80 × 450 = 360 HV
Standard Reference:
For 450 HV surface → Standard limit = 350 HV
(Calculated: 360 HV vs Standard: 350 HV)
• Minimum Surface Hardness = 450 HV
• Factor A = 0.80 (standard)
Calculate:
Hardness Limit = 0.80 × 450 = 360 HV
Standard Reference:
For 450 HV surface → Standard limit = 350 HV
(Calculated: 360 HV vs Standard: 350 HV)
Application Condition: Use SHD when hardness is less than (hardness limit – 100 HV) at distance 3 × SHD from surface.
Nitriding Hardness Depth (NHD)
NHD Limit = Core Hardness + 50 HV
NHD Calculator
NHD Calculation Result
Enter 3 core hardness values and click Calculate
Formula: NHD Limit = Core Hardness + 50 HV
Example Calculation
Given Core Measurements:
• H₁ = 245 HV
• H₂ = 253 HV
• H₃ = 247 HV
Calculate:
Average = (245 + 253 + 247) / 3 = 248.3 HV
Rounded = 250 HV (nearest 10)
NHD Limit = 250 + 50 = 300 HV
• H₁ = 245 HV
• H₂ = 253 HV
• H₃ = 247 HV
Calculate:
Average = (245 + 253 + 247) / 3 = 248.3 HV
Rounded = 250 HV (nearest 10)
NHD Limit = 250 + 50 = 300 HV
Core Hardness: Determined by minimum 3 measurements, rounded to nearest 10 HV
NHD Definition: Distance where hardness drops to core hardness + 50 HV
NHD Definition: Distance where hardness drops to core hardness + 50 HV
SHD Reference Values (ISO 18203:2016)
Standard hardness limit values for SHD calculation:
| Min Surface Hardness (HV) | Hardness Limit (HV) | Min Surface Hardness (HV) | Hardness Limit (HV) |
|---|---|---|---|
| 300-330 | 250 | 610-635 | 500 |
| 335-355 | 275 | 640-665 | 525 |
| 360-385 | 300 | 670-705 | 550 |
| 390-420 | 325 | 710-730 | 575 |
| 425-455 | 350 | 735-765 | 600 |
| 460-480 | 375 | 770-795 | 625 |
| 485-515 | 400 | 800-835 | 650 |
| 520-545 | 425 | 840-865 | 675 |
| 550-575 | 450 | 580-605 | 475 |
Measurement Guidelines
Test Parameters:
• Test Forces: 0.9807 N to 9.807 N
• Typical Forces: 0.9807-2.942 N
• Spacing: ≥3× diagonal distance
• Distance Accuracy: ±25 μm
• First Impression: ≥2.5× diagonal from surface
• Band Width: Maximum 1.5 mm
• Test Forces: 0.9807 N to 9.807 N
• Typical Forces: 0.9807-2.942 N
• Spacing: ≥3× diagonal distance
• Distance Accuracy: ±25 μm
• First Impression: ≥2.5× diagonal from surface
• Band Width: Maximum 1.5 mm
Special Measurements:
• THD: Microstructural method or hardness variation
• CLT: Microscopic measurement in micrometers (μm)
• Magnification: Layer occupies 1/3 to 2/3 of view field
• CLT Measurements: 10 within 5mm band (recommended)
• Multiple measurements required for statistical validity
• THD: Microstructural method or hardness variation
• CLT: Microscopic measurement in micrometers (μm)
• Magnification: Layer occupies 1/3 to 2/3 of view field
• CLT Measurements: 10 within 5mm band (recommended)
• Multiple measurements required for statistical validity
Measurement Validation
Validation Calculator
Validation Results
Enter values and click Validate
Distance difference must be ≤ 0.3 mm
Spacing must be ≥ 3 × diagonal
Spacing must be ≥ 3 × diagonal
Sample Preparation Quality:
• High-quality mounting with excellent edge retention
• Proper grinding and polishing sequence
• Appropriate etching for microstructural examination
• Clean surface free of films or residue
• High-quality mounting with excellent edge retention
• Proper grinding and polishing sequence
• Appropriate etching for microstructural examination
• Clean surface free of films or residue
