BS in Materials Engineering
Materials Engineering Department
Current hardfacing alloys provide insufficient wear resistance due to either cracking or significant material wear. To increase wear resistance of steel-based hardfacing alloys, the effects of composition on microstructure and hardness were investigated in a progression of alloys. Initially, seven new alloys were prepared varying the carbon-boron ratio with the total constant at 3 wt%. Small arc-melt cast circular ingots were produced roughly 1 x 0.5 inches. Metallography provided insufficient phase magnification, thus a SEM equipped with EDS was used, allowing for microstructure and phase composition analysis. Four distinct carbide phases were found and image analysis software allowed for carbide volume fraction measurements. It was determined that the sample consisting of 0.5 wt% carbon produced the most promising microstructure with a large volume fraction of NbC and M23(C,B)6 distributed in a continuous ferrite matrix. The 0.5 wt% C sample resulted in a hardness of 950 HV which exceeded the minimum 830 HV previous studies have shown to provide adequate wear resistance. XRD analysis alone produced inconclusive results, however by comparison to EDS compositions, phase stoichiometries were determined. A second round of new alloys was tested holding the composition similar to the 0.5 wt% C sample where vanadium was incrementally substituted for tungsten. These alloys demonstrated a reduced carbide volume fraction further supported with microhardness showing a reduction in the average hardness of 200 HV compared to the first round alloys. This suggests that the 0.5 wt% carbon sample shows the highest likelihood of increased wear resistance of the alloys tested. Overall, increasing the carbon content produced a M2,3C which in previous studies has been shown to be detrimental to the wear resistance of steel.