FEATURE ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2026 30 The micrograph of carburized case from one fully processed sample is shown in Fig. 4. Fine dispersed primary carbides are shown within the grains, and there are no grain boundary networks observed. DISTORTION MEASUREMENTS AND MODELING ANALYSIS After each processing step, two samples were pulled out to measure the distortion. Figure 5 shows photos of Almen strip samples after each process step: machining (18), normalizing (02), LPC (04), 1st normalizing (06), 2nd normalizing (08), 10-bar HPGQ (10); 1st temper (12), deep freeze (14), and 2nd temper (16, 17). The bow distortion was measured using a vertical dial gauge and granite block. The two distortion measurements after each processing step are consistent, as shown by the blue dots in Fig. 6. The consistency in distortion is due to two main factors: 1) samples were hung in the fixture, so the effect of the fixture on the sample cooling is minimized because there is no direct contact, and 2) very small thermal gradient in the thickness direction in the sample during quenching (<10°C), so the distortion caused by the thermal stress is negligible. All the processing steps were modeled using DANTE, as shown by the brown dots in Fig. 6, to compare with the measurements. The calculated dilatometry curves for Pyrowear 675 base carbon material and carburized material (0.9 wt% carbon) from the DANTE materials database are shown in Fig. 7. The heating rate is 1.0°C/s, and the cooling rate is 20°C/s. The x-axis in Fig. 7 is temperature, and the y-axis is linear strain due to the temperature change and phase transformations. With the starting phase being spheroidized body centered cubic structure (tempered martensite), the material volume increases during heating due to thermal expansion. When reaching the austenitizing temperature, material volume decreases Fig. 4 — Micrograph of carburized case from one fully processed sample. Fig. 5 — Photo of Almen strip samples pulled out at the end of di erent process steps. Fig. 6 — Comparison of simulated and experimental bow distortion at the end of each processing step. Fig. 7 — Calculated dilatometry curves for Pyrowear 675 from DANTE material database.
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