Identifying the effect of sodium dodecylbenzene sulfonate surfactant and dispersed pcb-based particles as a novel heat treatment quenchant on the hardness of S45C medium carbon steel

In this study, the effect of Sodium Dodecylbenzene Sulfonate (SDBS) addition as a surfactant on the performance of the Printed Circuit Board (PCB) particle-dispersed quenchant in terms of thermal conductivity, particle stability, the microstructure and hardness of S45C medium carbon steel has been investigated. Conventional quenchants have fixed, uncontrollable cooling rates. Adding solid particles creates a thermal bridge, enabling adjustable cooling rates to address this limitation. The solid particles in the quenchant were synthesized from PCB. The surfactant helps to improve particle dispersion and avoid agglomeration by modifying the surface tension between the particles and the fluid. PCB particle-dispersed media have been prepared and used as quenchants to study the effect of PCB dispersion, and its concentrations on the heat transfer rate during quenching. Based on this research results, particle stability measurement by zeta potential shows the stability improvement up to –21.53 mV after 7wt % of surfactant addition, compared to distilled water. Due to the better particle dispersion, the thermal conductivity of the quenchant is also improved by 39 %, maximized at 0.82 W/mK when compared with the quenchant without surfactant at only 0.61 W/mK. Furthermore, the quenched steel hardness also increases by 29 %, maximized at 58 HRC at 7wt % surfactant and 0.3wt % PCB particles composition. The Dispersed PCB particles in the quenchant allow the heat flow from high to lower temperature efficiently. The experimental results show that a water-based quench medium with PCB particle dispersion is an alternative quench medium to obtain a more controlled cooling rate in steel heat treatment and is one solution for utilizing PCB electronic waste