where X is the normal force (see Figure 1).

Results and discussion

Overall, HSS heat treated to a high hardness wore less than HSS heat treated to a low hardness (Figure 1). However, some HSS grades showed

better wear resistance over other grades that had increased hardness. For example, M2 (Rc 65.5) had a higher wear index (1/X) and a lower normal force than T15 (Rc 66.3), as shown in Figure 1. Other examples in Figure 1 show that HSSes of the same hardness had different wear

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indexes.

Generally, harder tool materials are more resistant to chemical attack at elevated temperatures (refractory) and/or are better heat conductors. The data in this study suggest that this factor may explain the variation in wear resistance for different HSS grades with the same hardness. For example, the analysis of variance for the normal tool force at the high hardness heat treatment shows M2 had a lower force than T15, but T15 was slightly harder than M2. Further, M2 is the same hardness as Vasco Wear at the low hardness heat treatment but their mean normal tool forces are not the same (although they are not statistically different). Hence, chemical attack or hot corrosion could be responsible for some of the wear resistance observed.

Although hardness
is a general indicator
of wear resistance in
HSS tools, other factors
influence wear.

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An HSS within each high- or low-hardness heat treatment may not necessarily wear less, as indicated by an inspection of the mean tool forces alone (Figure 1). For example, Alloy Z has the lowest mean tool forces in the low hardness heat treatment, but Alloy Z is also slightly harder than the other HSSes. If the tool steels had the same hardness, the results could be different. The various alloying elements may affect the wear resistance because they affect the hardness, carbide composition, volume fraction and chemical reactivity.

The combination of alloying elements influences wear resistance. Alloy Z also includes aluminum, which in iron alloys has been shown to reduce high-temperature corrosion and oxidation. Because high-temperature mechanisms have been shown to cause wear in wood

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