Non-destructive measurements of large case depths in hardened steels using the thermal-wave radar

The thermal-wave radar method was used to resolve and measure deep hardness case depths (2–3 mm) of AISI9310 and Pyrowear53 steels used in the aerospace industry. Several gears made of these steels were evaluated and correlations between radiometric signal and case depths were obtained using the cross-correlation peak delay time. The foregoing case depth range is significantly deeper than achievable with point-by-point laser frequency scans (800 μm) and swept-sine modulation of the laser beam (1.16 mm).

► Measurements of deep hardened case depths of steel using the concept of thermal-wave radar. ► Monotonic increase of cross-correlation peak delay time with case depth increase. Resolution of case depth up to 3 mm. ► Pulse-compression enhanced SNR of thermal-wave radar compared to frequency-domain PTR.