De Moor, EmmanuelSpeer, J. G.Brown, Casey S.2022-10-102022-10-102022https://hdl.handle.net/11124/15396Includes bibliographical references.2022 Spring.The mining industry strongly depends on milling operations to promote mineral liberation in extracted ore by reducing particle size. The purpose of this project was to assess the effect of niobium alloying and microstructure on the performance of grinding media via Nb alloying. If beneficial to wear performance, a cost reduction in grinding media use for mining applications may result. Experimental laboratory-prepared heats were produced via vacuum induction melting industrial bar stock with a base composition of Fe-1.0C-0.96Mn-0.22Si-0.26Cu-0.11Ni-0.50Cr-0.005V-0.012Nb and additional incremental alloying of Nb. Four different ingots were cast with Nb contents of 0.01, 0.25, 0.5, and 1.0 wt pct. Light optical microscopy (LOM), scanning electron microscopy (SEM), bulk hardness measurements, and X-ray diffraction (XRD) were conducted to characterize the lab processed material. SEM revealed eutectic niobium carbide (NbC) networks that were effectively broken up and distributed within the microstructure during hot rolling. Dilatometry was performed on industrial bar stock and hot rolled Nb-added laboratory prepared materials in order to design a heat treatment to replicate current grinding ball properties. The martensite start (Ms) temperature was found to increase with increasing Nb content from about 187 °C to 216 °C for the 0.01 and 1.0 wt pct Nb alloys, respectively. An increase in hardness was observed as a function of Nb content, with a total increase from 63.3 ± 0.5 to 65.4 ± 0.2 HRC for the 0.01 and 1.0 wt pct Nb alloys, respectively. This trend is attributed to the increasing volume fraction of the hard NbC phase. All samples had a retained austenite content of approximately 20 ± 5 vol pct with no clear trend between austenite content and Nb alloying. Volume fraction of eutectic-containing NbC was measured using SEM micrographs and ImageJ® image analysis software. An increase in the eutectic volume fraction of approximately four times was observed between the 0.01 and 1.0 wt pct Nb alloys. However, an increase in NbC content led to a decrease in solute C in the matrix, possibly decreasing the hardness of the martensite and an increase in Ms temperature. Bond abrasion and dry sand/rubber wheel (DSRW) wear tests were performed to evaluate wear resistance as a function of Nb alloying. Bond abrasion testing was performed using both iron and copper ores. Bond abrasion results revealed that there was no discernable increase in wear resistance with increasing Nb content. DSRW results showed, however, a clear decrease in wear with an increase in Nb alloying with a 65 pct decrease in mass loss observed between the 0.01 and 1.0 wt pct Nb alloys.born digitalmasters thesesengCopyright of the original work is retained by the author.abrasiongrindingminingsteelwearText2022-10-01