February 2020 Volume 2

FORGING RESEARCH

Table 2: Summary of friction factor values for un-coated steel inserts measured at room temperature without lubrication.

Figure 9: Impact of testing temperature on the friction factor for un-coated steel inserts tested using graphite lubricant.

Figure 8: Impact of lubrication condition on the friction factor for un-coated steel inserts tested at room temperature. As shown in Figure 8 and Table 3, when lubricated with either Molykote or graphite, the room temperature friction factor for the un-coated steel inserts was significantly reduced, with the average friction factor with Molykote being 0.12 and with graphite being 0.30. Table 3: Summary of friction factor values for un-coated steel inserts measured at room temperature with lubrication.

Figure 10: Impact of testing temperature on the friction factor for un-coated steel inserts tested using Molykote lubricant. Table 4: Summary of friction factor values for un-coated steel inserts measured at elevated temperatures with lubrication.

The impact on the friction factor of testing the un-coated steel inserts at elevated temperatures with lubrication is shown in Figures 9 and 10 and summarized in Table 4. These data show that the friction factors for bothMolykote and graphite lubricants are similar at 100°C as for room temperature testing, but for both lubricants the friction factors increased significantly when tested at 200°C. As summarized in Table 4, for Molykote, the friction factor at 200°C increased to 0.38, and for graphite increased to 0.80, the latter being similar to the friction factor for the unlubricated steel inserts at room temperature (see Table 2).

Nitrided Steel Inserts Table 5 shows the average friction factors for nitrided H13 steel inserts tested at room temperature. In the un-lubricated condition, the average friction factor for a series of six tests performed on the same inserts was 0.81, but as shown in Figure 11 the friction factor changed from 0.67 for the first test to 0.90 for the last two. This change is likely due to build-up of aluminum on the surfaces of the steel inserts. This high level for the friction factor suggests that the nitriding process provides little benefit in friction reduction relative to un-coated steel inserts. Similar to the un-coated steel inserts, when tested with lubricants the friction factors for the nitrided inserts dropped. As shown in Table 5, the average friction factor for the nitrided inserts tested using Molykote was 0.20, and when tested with graphite was 0.37.

FIA MAGAZINE | FEBRUARY 2020 57