Analysis of Gage R&R Hardened Depth Variability, Process Potential and Measurement Error Assessment in Case Carburized Components

Hardened depth, or effective case depth, measurement is one of the most commonly used methods to evaluate the quality of carburized or carbonitrided parts.  In industry, it is not uncommon to observe application of statistical control requirements on the hardened depth measurement without taking into account the capabilities of the measurement system and indirect nature of the hardened depth measurement.

Gage R&R studies were conducted at 3 different metallurgical laboratories on shallow and deep case carburized components to understand typical hardened depth measurement variation. The primary objectives were to 1) identify controllable and uncontrollable sources of hardened depth measurement variation, 2) understand the magnitude of the measurement uncertainty and heat treat process variability, and 3) evaluate practical applicability of statistical control to metallurgical quality assessment.