Feb_March_AMP_Digital

FEATURE A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 2 0 4 1 for parts located in the racks either with their flange to the top or to the bottom. The values for the heat-treated condi- 9 tions correspond to the average of three individual shafts, whereas those for the machined condition are from the 24 shafts involved in the test. The values for the run out in the as-machined condition were within the 15 to 30 μm range in all the measured positions. The measurements indicate that the way the shafts are located within the racks have a major effect on the run out. All the values obtained in shafts with the flange on top fall below the 200 μm mark, whereas some regions in the shafts with their flange toward the bot- tomhave values greater than 200 μm. Not much difference is found when comparing the run out of shafts using different quenching media. Figure 4 shows the values in length of the shaft, and the difference in size froma perfect circle (roundness) of the part in various conditions. It is noted that the increase in harden- ability of the steel tends to increase the length of the shaft, and reduce the roundness of the gear. No clear difference be- tween the positioning of the flange or the quenching media is observed. The case hardening depth toward the center of the shaft and at the flank of the gear teeth are shown in Fig. 5. It is observed that the steel hardenability has a major affect on these depths, which are higher in the steel with the low- er hardenability. The use of oil as a quenchant resulted in a greater depth compared to using nitrogen. Figure 6 shows the hardness values at the core of the shaft and the surface residual stresses. Both values were measured toward the center of the shaft. The data shows that an increase in hard- enability and the use of oil increases core hardness. Use of nitrogen as a quenching media results in the tendency for positive, tensile, stresses in the shaft, whereas use of oil al- lows for compressive stresses. Positioning the shaftswith the flange either on top or bottom does not seem to affect this parameter. Fig. 3 — Changes in run out in different places of the shaft. Fig. 4 — Changes in length and roundness of the gear. Fig. 5 — Variation of the case hardening depth. Fig. 6 — Changes in core hardness and residual stresses.