New Horizons of Science, Technology and Culture Vol. 12

Steam and chemical activation techniques are widely used in the production of activated carbon. Agricultural wastes that were previously disregarded are increasingly being utilised to enhance engineering products, including the case hardening of steel surfaces. This study investigated the use of walnut shell powder for case hardening steel. The walnut material was obtained from trees at Itaogbolu, Ondo State, Nigeria. It was divided into two portions: one was pre-treated, while the other was used as received. The material was cleaned and broken to separate the shells, which were dried, ground using a roller mill, and further pulverised using a mini-pulveriser. The resulting powder was sieved to obtain a particle size of 36 microns. Pre-treated and as-received powders were used at 850°C with soaking times of 45, 60, and 75 minutes, designated A, B, and C, respectively. Uniaxial tensile testing was used to characterise the tensile properties and fracture toughness, while a metallurgical microscope was used to examine and analyse the sample microstructures. Sample A1, case-hardened in pre-treated walnut shell powder at 850°C for 45 minutes, exhibited a favourable combination of improved properties and a distinctly refined, more compact grain structure at the microstructural edge. This observation was attributed to carbon diffusion from the carburiser into the sample surface. Overall, the study evaluated pre-treated and as-received walnut shell powders at a fixed temperature and varying soaking times for the case hardening of steel.