How accurate are these calculations?

The calculations are based on peer-reviewed empirical equations and established engineering standards (ASME, EN, ISO, ASTM). Accuracy depends on: (1) accuracy of input data (steel composition from mill certificate, not nominal); (2) applicability of the equation to the specific alloy (most are calibrated for carbon and low-alloy steels); (3) whether equilibrium conditions apply. For design-critical applications, always verify against material certificates and applicable codes.

Are these calculators suitable for design use?

These calculators are suitable for preliminary design, engineering checks, and educational purposes. For final design and qualification of safety-critical pressure equipment, structural connections, or weld procedures, calculations must be performed by a qualified engineer using the exact applicable code (ASME VIII, EN 13480, AWS D1.1, etc.) and verified by approved calculation methods. The calculators do not replace code compliance.

What units does the calculator use?

All calculators use SI units (°C, MPa, mm, kJ/mm, g/cm³) as primary output, with imperial conversions (°F, ksi, inches, J/in) provided where common in industry practice (particularly for ASME and AWS codes used in North America). Input and output units are clearly labelled in each calculator field.

Carburising Case Depth Calculator —

Estimate the theoretical diffusion case depth for carburising, nitriding, or carbonitriding using Fick’s Second Law of diffusion. The calculator uses the semi-infinite slab solution (error function complement) to determine the carbon or nitrogen concentration profile and the depth at which the composition reaches a specified threshold value.

Diffusion Case Depth Calculator (Fick’s Law)

Process type

Diffusivity D (m²/s) — auto-set or override

Process time — t (hours)

Surface concentration — Cs (%C or %N)

Initial bulk concentration — C0 (%C or %N)

Threshold concentration for case depth (%C or %N)

√(D×t) — diffusion length parameter—

Theoretical case depth (x at Cth)—

Effective case depth (mm)—

Depth at 90% surface concentration—

Fick 2nd Law (semi-infinite, constant surface conc.):
C(x,t) = Cs − (Cs−C0) × erf(x / (2√(Dt)))
Case depth x = 2×√(Dt) × erfinv((Cs−Cth)/(Cs−C0))
Effective case depth (ECD) defined at threshold concentration Cth

Figure: Schematic diagram for Carburising Case Depth Calculator — Fick's Law Diffusio… — key process, structure, and property relationships. © metallurgyzone.com/

References

Callister, W.D. and Rethwisch, D.G., Materials Science and Engineering. 10th ed. Wiley, 2018. Chapter 5: Diffusion.
ASM Handbook Vol. 4A: Steel Heat Treating Fundamentals and Processes. ASM International, 2013.

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