Hydrogen Embrittlement Electrodeposition of metals

[facthunter]

I havent seen any thing on the above . since a lot of people like to make things look nice about their aeroplanes & there is real need to reduce corrosion & the above process is utilised frequently there are real hazards involved Lets get some information out. N.....

 

 

[facthunter]

this topic seems to be sitting dead in the water.Dont be put off by the complex sounding title I found out the hard way many years ago about the effects of this phenomenon with the crankshaft of a race car It was (&still is) reasonably common to reclaim spoiled journals oleo's etc. by hardchroming & resizing by grinding. The crank was cracktested,& processed as described & the engine reassembled & run.Didn't even get to select a gear before the shaft failed completely through the journal at quite low RPM. Upon enquiry I was told it was due to hydrogen embrittlement & that heat treatment was required to correct it . For my own work (motorcycle spokes etc.) I put them in an oven at about 300.c Most people I speak to don't want to know about it In aircraft situations there is no room for this approach. It could be assumed (I hope) that in an aircraft shop the proper procedures would be carried out ,but in any other outsource situation most unlikely.I personally Know little more than I have written here & am seeking more info & to alert others ( lets put the CRAFT into airCRAFT. N.....

 

 

[Guest micgrace]

Hi

 

I have come across a couple of crankshaft failures and it's not pretty . I traced the problem to incorrect radiusing on the fillet web. This was then traced to incorrect dressing of the crankshaft grinding stone by the operator.

 

Interestingly they seemed to happen very shortly after a rebuild, where common sense would suggest failure would not happen for many hours.

 

I never had a problem with reclaimed journals which I specified by submerged arc welding and not to placed in the fillet web area. Of course, the entire article was raised to about 300*C to begin. Myers Bro's engineering do this sort of thing, but i haven't had one done in 20 years, so I cannot be sure even if they exist anymore.

 

Preferable was to just get a replacement, but sometimes this was just not possible (likes of antique engines, expensive/unobtanium parts.)

 

Possibly by hard chrome plating your example, they may have intruded upon the critical fillet web (very high stress) and left an "edge" to quickly form into a crack leading to failure. as for hydrogen embrittlement, I would expect a failure from this to occur in a very thin layer, and at worst, I would expect the laid down material to separate from the parent substrate, but not for the entire piece to crack.

 

Just my 2cents worth,

 

Micgrace :)

 

 

[facthunter]

Thanks Michael , all of what you say is correct. The source of my revelation was Newcastle university which was an annex of the university of Technology (Univ of NSW). They had a pretty extensive section devoted to this kind of research. and may still have, but I doubt it. Of course, nobody is infallible The major airlines used to have electroplating sections,Handling all this work in house there should be procedures specified I will try to obtain more on this.I would advise repairers not to use replated parts in critical load bearing situations.N....