On Tungsten Carbide Drill Bits Wear When Drilling Hematite Ore

摘要

In the South African mining industry WC-Co drill bits perform poorly when used in the drilling of hematite ores, but the cause of their high wear rate is unclear. This paper reports preliminary results of the attempt to simulate the drilling of hematite ore using WC-Co drill bits by means of high energy ball milling (the impact among the particles were taken as simulating the impacts between WC-Co bits and hematite rock). Dry milling of WC-Co (sintered) powder, hematite powder, WC and Co powders (unsintered) was performed using a PM400/2 high-energy planetary ball mill, for different milling times. The effects of milling for different times on the individual and composite powders were studied. XRD and Mossbauer spectroscopy (MS) were used to characterize any possible phase transformation induced to the system. XRD peak broadening as a result of extensive material structure distortion was observed for a protracted milling of (30 hrs). Substantial phase transformation after milling i.e. disappearance of contaminated hematite and the appearance of new mixed Co, iron-bearing phases as revealed by MS will be discussed. Emerging new phases characterised by two hyperfine interaction doublets: doublet 1 (δ_(Fe) =0.40-0.71 mm/s, Δ=0.69-1.85 mm/s) and doublet 2 (δ_(Fe)=0.69-0.97 mm/s, Δ=1.64-1.90 mm/s). and an additional sextet(s) were observed.