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The material is UNS S42716. It was supposed to be heated to 1925 °F (1052 °C), held at heat for 30 minutes, quenched in oil, sub-zero cooled to -100 °F (-73 °C), held for 2 hours, warmed in air to room temperature and tempered at 350 °F (177 °C) for an hour. Is the black discoloration a heat...

MintJulep, AS = Aerospace Standard. Pretty sure it's GE Aviation division. GE spec's installation torque has no mention of preload/axial load at all, the protrusion is what defines the "installed" state for the max installation torque.

SWComposites, sign...as if these countless different torque names are not confusing enough already, and who came up with these names, my god. They might as well as remove the words and name these torques with number sequences, so we know exactly what phase the torque belongs to.

In the case of self-locking nut. Is it normal to have different definitions across different specs, within the same industry? I am so confused, AS spec should in theory be aligned with GE spec. However, I am not seeing that, am I interpreting it correctly? AS spec says: Assembly torque is the...

Thanks Ed, the actual mating bolt is made of Inconel 718 with a min hardness of 36 HRC. I wonder why they allow the nut hardness to be 32 - 44 HRC and the test bolt to be 32 - 42 HRC in the first place.

dvd, I am not seeing a direct correlation between the proof load test and the wear on the thread.

Thanks Dave, definitely going to try that first.

Tugboat, The nut needs to be reusable; the test assembly is only used for a single test run (15 cycles). I don't believe it's meant to be re-plated; the test procedure only allows oil lubrication in-between cycles.

The supplier informed us that the test bolt threads are experiencing wear during a reusability test for a self-locking nut. They observed a change in thread dimensions after just 2-3 cycles, along with increased heat generation. The nut is silver-plated and waxed, and it is crimped to create the...

this one was taken side by side with the yellowed part.

Thanks for the info. The supplier said that the yellowing is due to the plastic compound. I also noticed that yellowing due to polymer chain degradation is typically uniform, the yellowing on my part appears to be different, resembling a pattern of the natural movement of viscous fluids. Does...

I agree the lighting is bad. The color meter was using the previous good parts as reference, so it does not have to be on the upper piece. See a good part below, would the yellowing in my original post equivalent to a delta-E of >3?

Using a color meter or spectrophotometer to measure the variation between the area in the red circle and the upper area, what would be the approximate delta-E? I have never used such a tool, but my supplier is saying it's less than 3.0 and is acceptable. But since it's clearly visible to naked...

CWB1, Good point, I will double check with the supplier. What's BJA? Bolt joint assembly?

TugboatEng, Having the same material would make the galling issue worse, no?

mfgenggear, The DFL's max operating temp is 800 F. The drawing calls for a spec which requires reusability test, this spec (active since 1985) is used for other similar nuts as well, I would have to assume it can be reused under some conditions, otherwise, I don’t see the point of the testing...

Ed, The picture above is all I have right now, it looks like a lot of material is stripped off. The previous supplier did not have this issue, and the new supplier have been having issues with parts lately.

Dave, The required dry film lubricant is EVERLUBE® ESNALUBE™ 382 Gray PWA-36545T Spec Low VOC Thermally Cured Mos2 Solid Film Lubricant, pretty much exactly what you said. The spec does require coating the lubricant prior to any 750 F+ heat and allows the coating to be reapplied between cycles...

The new supplier stated that the thread of the nut is chipping out during the first removal cycle after baking (image attached) and the nut is getting stuck after 3-4 cycles of room temperature torque test. https://imgur.com/a/c18sqkU .190-32 UNJF Nut material: A286, hardness 24- 37 HRC, 130...

Yes, that's correct