The effects of leaching and pyrolysis on particle synthesis and their impact on thermal conductivity and cooling rates of waste PCB-dispersed quenchants

Abstract This study investigates the effects of pre-treatment processes—leaching and pyrolysis—on synthesizing particle-dispersed quenchants derived from waste printed circuit boards (PCBs) for enhanced heat treatment applications. The process begins with milling PCB powder with and without pre-treatment, followed by thermal conductivity and cooling rate analysis of synthesized quenchants. Findings reveal that full pre-treated particles, which undergo leaching and pyrolysis, achieve significantly smaller sizes, up to 80.4%, compared with the half-pre-treated particles. The better improvement was due to the breakdown of epoxy resin used in the PCB. The particle size reduction enhances the quenchant’s thermal conductivity up to 17.47% for the quenchant with 0.5% dispersed particle. Similarly, the maximum cooling rate was improved by 16.93% for the same quenchant. Quenching tests on S45C medium carbon steel demonstrate that particle-dispersed quenchants increase the hardness of the quenched steel, maximized at 57.8 HRC, because of the higher density of the Martensite phase developed by the higher cooling rate. This research highlights the value of pre-treatment in optimizing quenchant performance, with potential implications for improved efficiency in industrial heat treatments.