Indentation fracture toughness of boronized unalloyed and alloyed ductile iron

Abstract

This study was carried out to investigate the fracture toughness of boride layers in ductile irons using a Vickers indentation method and to demonstrate the method's reliability. For this purpose, alloyed (Cu, Ni, and Mo) and unalloyed ductile cast irons were borided for 2, 4, 6, and 8 h at 900 and 950 °C temperatures. The morphology of the boride layer was studied using an optical microscope. The hardness profiles and thicknesses of the boride layers were measured. Boron compounds were discovered using the X-ray diffraction method. The fracture toughness of the boride layer was tested using the Vickers indentation method under a 300g load. In unalloyed cast iron, the surface hardnesses obtained by boriding were 5, 45-6, 69 times higher than that of the unboronized iron hardness. In general, alloyed iron produces thicker boride layers under the same boriding parameters. Depending on the boriding time, the fracture toughness increased at 900 °C and decreased at 950 °C in both types of cast iron.