Two-Stage Nitride Calculator

Floe process · case depth ↔ time · split-temperature cycle · AMS 2759/6 planning aid

Inputs

Depth to core hardness + 50 HK by microhardness traverse, off the drawing.

Valid 925–1050 °F each. Stage 2 is often bumped 25–50 °F above stage 1.

Off the cert. Both stages must run at least 50 °F below this or the core softens.

Cycle result

Required total time at temp
— hr
Stage 1 · low diss
— hr
builds surface nitrogen
Stage 2 · high diss
— hr
dissolves compound layer inward
Total time
— days
Typical surface hardness
—
Governing temp ceiling
— °F
grade limit
—
temper − 50 °F
—

Excludes heat-up, purge, stage transition, and cool-down. K is time-weighted across both stages (1/3 · 2/3 split per Bennett practice) with a 3% two-stage depth credit.

White layer estimate

Single-stage (reference)
— in
Two-stage estimate
— in
Reduction vs single-stage
—

—

Literature placeholders, not Bennett data. White layer is furnace- and potential-specific; replace with your own metallography. The two-stage number assumes stage 2 dissociation actually reaches its target.

Atmosphere setpoint check

Pick whichever your furnace actually controls on. The two describe the same condition — don't satisfy both.

Stage 1 target
—
Stage 1 reading
—
Stage 2 target
—
Stage 2 reading
—

Reverse check

Audit an existing cycle sheet: what depth does a planned time actually yield?

Case depth from planned time
— in

Nitrogen diffusion K referenced to 4140 · ASM Handbook Vol. 4A. Piecewise-linear K interpolation matching the workbook. Planning aid only — case depth and white layer must be verified per AMS 2759/6 and the customer specification.
Bennett Heat Treating & Brazing