Fig 2 Iron carrier pinion gear dimensions in inches

The primary findings of the study are summarized in the tables and figures discussed below. The fully sintered gears provided the best overall density, at 7.84 g/cm3 (see Table 1). Sectioning the gear into top, middle, and bottom shows that the density gradient present in the pre-PIF condition remained but density in each area significantly improved. The delubed (or presintered) gears showed lower average density than the fully sintered parts. The overall average density was 7.8 g/cm3. The gradient remains although, as in the sintered gears, each area shows significant improvement.

Table 1 Pinion gears densified by PIF

Heat treat condition

Weight, g

Density, g/cm3

Average Top

Middle

Bottom

As-sintered

133.25

7.340 7.343

7.270

7.346

Sinter/PIF

133.72

7.836 7.854

7.760

7.863

Sinter/PIF

133.92

7.837 7.836

7.812

7.862

Sinter/PIF J

133.75

7.837 7.836

7.800

7.860

Presinter/PIF

132.19

7.802 7.849

7.712

7.851

Presinter/PIF

131.56

7.796 7.853

7.712

7.851

Hardness is a significant characteristic of the quality of a gear. In Table 2, the hardness values are charted for the full sintered and delubed (or presintered) conditions after PIF. As a matter of comparison, a sinter/PIF gear shows improvement in hardness over sinter only. The presinter/PIF shows lower values for hardness simply because of the absence of sintering.

Table 2 Pinion gear hardness (Rockwell B) in post-PIF condition

Heat treat

Section

Hardness

Average

condition

top/bottom

reading, HRB

As-sintered

Top

83, 83, 84, 85

84

Bottom

83, 84, 84, 85

84

Sinter/PIF

Top

100, 99, 100, 100

100

Bottom

100, 100, 101, 102

101

Sinter/PIF

Top

100, 99, 100, 100

100

Bottom

102, 101, 100, 101

101

Sinter/PIF

Top

101, 100, 99, 99

100

Bottom

102, 101, 101, 101

101

Presinter/PIF

Top

89, 89, 88, 90

89

Bottom

88, 89, 88, 86

88

The metallographic observations also confirmed the findings in Table 1. Figure 3 shows the pronounced effect of combining sintering and PIF.

Fig. 3 Unetched microstructure of iron carrier pinion gear. (a) As-sintered condition. (b) Top surface of the tooth after pneumatic isostatic forging. 48x
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