Chemical Strengthening of Soda-Lime Glasses via Ion Exchange Method

The aim of this study is to improve the mechanical properties of glasses by the chemical strengthening method via the ion-exchange technique. For this purpose, KNO₃ salt baths were utilized for commercial soda-lime glasses. The diffusion-controlled strengthening mechanism is based on creating the compressive stress on the surface of glass by displacing the larger potassium ions with sodium ions. SEM-EDS line scan and XRF analysis, four-point bending, and Vickers hardness tests were performed for the structural and mechanical characterization of ion-exchanged glasses. The optimization of parameters led to a treatment duration of 24 hours at 400°C, resulting in a penetration depth of K⁺ ions reaching 85 µm. After ion exchange process, the improvement in the hardness, fracture toughness as well as bending strength values of the glasses was observed. The strengthened glasses exhibited notable enhancements in mechanical properties, specifically, hardness increased from 517 HV to 612 HV, and the fracture toughness increased to 3.14 MPa.m^1/2 compared to the untreated glass, which displayed the fracture toughness of 1.09 MPa.m^1/2. Furthermore, the bending strength of treated specimens significantly improved to 421.6 MPa, representing a five-fold increase over the untreated sample's bending strength of 79 MPa.