February 2020 Volume 2

Graphite

SiC

RT RT

1 2

0.50 0.42

DLC

FORGING RESEARCH

Table 9: Summary of friction factor values for PVD coated steel inserts measured at elevated temperatures without lubrication. Table 9: Summary of f iction factor values for PVD coated ste l ins rts mea ur d at levated temperatures wi hout lubrication. Table 9 shows the impact on the friction factor of testing the i-Kote and Super MoS 2 coated inserts at elevated temperatures without lubrication. Again, the i-Kote coating had the lowest friction factor.

Temperature ( o C)

No of samples tested

Ave. Friction Factor (m)

Coating

Lube

i-Kote

None None None None

100 100 200 200

4 4 4 3

0.44 0.84 0.63 0.82

TiCN

i-Kote

Super MoS 2

A second series of tests were performed at elevated temperatures using the i-Kote and Super MoS 2 coated samples, but after the coated inserts had been left in a furnace preheated at about 250°C. After the samples were placed in the furnace, the power to the furnace was turned off and the samples allowed to slowly cool to room temperature. The samples were then re-tested, and as shown in Figure 10, the friction factors were much higher, suggesting that the furnace treatment had damaged the coatings. Therefore, the thermal stability of the i-Kote and the Super MoS 2 coatings needs to be examined in more detail in future research. Table 10: Summary of friction factor values for PVD coated steel inserts measured at elevated temperatures without lubrication after the coated inserts had been left in a furnace at about 250°C. 17 A second series of tests were performed at elevated temperatures using the i-Kote and Super MoS 2 coated samples, but after the coated inserts had been left in a furnace preheated at about 250°C. After the samples were placed in the furnace, the power to the furnace was turned off and the samples allowed to slowly cool to room temperature. The samples were then re-tested, and as shown in Figure 10, the friction factors were much high r, suggesting that the furnace treatment h d damaged the coatings. Therefore, the th rma stability f the i-Kote and the Super MoS 2 c atings needs to be examin d in mor detail in future research.

Figure 14: Aluminum build-up on steel insert with i-Kote coating after one forging trial.

Figure 15: Aluminum build-up on steel insert with i-Kote coating after eleven forging trials. Table 8 lists the friction factors for three of the PVD coated inserts tested at room temperature with either Molykote or graphite lubricant. As with the un-coated inserts, the friction factor dropped with the use of lubrication, with the reduction being largest for the TiCN coating, but smaller for the SiC and the DLC coatings. Table 8: Summary of friction factor values for PVD coated steel inserts measured at room temperature with lubrication

The second set of samples coated with i-Kote were also tested at elevated temperatures (see data in Table 11). When tested at room temperature this second set of samples coated with i-Kote had a slightly higher friction factor (0.51) than the first set of samples (0.35), but the friction factor of this second set of samples coated with i-Kote was essentially unchanged at 100°C or 200°C (see Table 11). Again, the reason why the behavior is different than for the first i-Kote inserts (data shown in Table 9) is unclear, and would need to be a subject for future research. Table 11: Friction factor values for second i-Kote coated steel inserts measured at elevated temperatures without lubrication

Table 9 shows the impact on the friction factor of testing the i-Kote and Super MoS 2 coated inserts at elevated temperatures without lubrication. Again, the i-Kote coating had the lowest friction factor.

Finally, data in Table 12 shows friction factor values for TiCN coated steel inserts measured at 100°C with lubrication. These values are similar to un-coated H13 steel inserts tested under the same conditions (see Table 4).

FIA MAGAZINE | FEBRUARY 2020 59