Fracture toughness evaluation using Palmqvist crack models on AISI 1045 borided steels

The present study evaluates the fracture toughness on Fe₂B borided layers. Formation of the layers was obtained by means of the paste boriding process on an AISI 1045 steel surface. The treatment was carried out at temperatures of 1123, 1173, 1223 and 1273 K for 8 h using a 4 mm thickness layer of boron carbide paste over the material surface. A Vickers microhardness tester was used to generate microcracks under loads of 1.9, 2.9, 4.9 and 9.8 N at different indentation distances across the thickness of the iron boride layer. The applied loads and the crack lengths generated from the corners of the indentations were set as the experimental parameters, using two Palmqvist cracks models, for the evaluation of the fracture toughness. Finally, the fracture toughness results in the borided layers were analyzed based on the different distances from the surface, microindentation loads and the treatment temperatures of the paste boriding process.