Ni3Ti effects on strength and hardness of bolts

[GunnyD]

We are experiancing failures of the splines on a stake stud. The splines are loosing their integrity when the stud is pressed into the mating part (essentailly they are being "rubbed/smeared" away). Any help on this issue would be greatly appreciated.

 

[CoryPad]

For the benefit of others reading this thread, here is a link to a previous thread on this subject:

thread90-155727



Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[GunnyD]

Cory, thanks I didn't think about linking this to our past postings. I am still looking for any help on understanding if this condition would have any effect on the stud. We did have the splines tested for microhardness. We discovered that the splines on our stud are significantly softer than our competitors. The lab reported they checked with Knoop 500-g microhardness in the splines at approx .003" depth the results are (converted to Rockwell C) ours 24.5-25.8 the competitors = 34.1-34.6. They stated that going a little bit deeper the microhardness went up to 31.5 HRC. They stated that the lower values seemed to coincide with the microconstituent that was visable in the images of the etched samples. Early on during this investigation we were told that this "microconstituent" (a dark area on the perimiter of the part visible on the micrographs of the etched part) was called an EtA phase. Again Cory thanks. Anybody out there with any suggestions they would be greatly appreciated as we are at a dead end.