Root Cause Analysis of Quench Cracking in Industrial Hand Tools: A Case Study

This case study investigates the origin of cracking in industrial hand tools manufactured from 5160R alloy steel following hardening in a PVP polymer quench. To identify the root cause, an exhaustive metallurgical evaluation was performed on multiple specimens, including polymer solution analysis and cross-sectional inspections in both transversal and longitudinal directions.

Characterization utilized optical microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS) to evaluate the microstructural integrity and chemical composition of the failure sites. Analysis focused on the morphology of observed transgranular cracks, micro-tears, and the presence of surface phenomena such as decarburization and oxide layers. By examining the relationship between the martensitic matrix, oxygen concentrations within the crack paths, and manufacturing-induced features like forging laps, this study delineates the contributing factors leading to crack propagation during the quenching process.