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I've asked several people and gotten mixed answers, so I've decided to post the question here. Can steel be electroplated onto steel to build up worn surface areas (I'm talking about less than a millimeter). For example, could a worn knife edge be electroplated back on? I know for large worn areas, hardfacing is used. What, if any, technique can be used to rebuild small, worn steel surfaces?

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    $\begingroup$ What kind of object is this? Are we talking about an actual knife edge? Or a wear surface? Made of any old steel? Or made of carefully selected, forged, and heat-treated steel? The type of wear and hardness that matters for a knife is not the same as that for a bearing surface. $\endgroup$
    – DKNguyen
    May 10 at 17:15

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For specifically a knife edge - no. A steel blade is iron but with specific amounts of carbon ,manganese, chrome , and possible other alloy elements. They either do not , or do not predictably transfer in electroplate. Then it would need to be heat treated. Steel build-up is done with welding processes. I once built up lawnmower blades edge with steel hardfacing. The weld left a smooth rounded surface which was nearly impossible to grind to a cutting edge. So welding is not useful either.

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  • $\begingroup$ Thank you. What is the smallest object that could be hardfaced? $\endgroup$
    – Justify
    May 10 at 15:46
  • $\begingroup$ @Justify obviously larger than a lawnmower blade. $\endgroup$
    – Solar Mike
    May 10 at 16:52
  • $\begingroup$ Hard chrome and flame spray ( eg. D-Gun) can be put on thin steel. The devil is in the details. $\endgroup$ May 10 at 18:26
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building up worn parts like the bearing surfaces of a crankshaft is commonly done by electroplating- after plating, the part is then finish-ground to the exact size required. But note that there is a risk of ruining the fatigue resistance of the built-up part if the electroplating process happened to generate hydrogen on the plated part. This will diffuse into any microcracks in the part's surface and significantly embrittle it.

BTW hard-faced lawnmower blades are almost impossible to grind on purpose, because they are supposed to be abrasion-resistant. You have to use diamond grinding wheels to sharpen hardened parts like that.

BTW^2 a clever trick on a mower blade is to hard-surface only one side of the blade. the hard-surfaced side is more resistant to abrasion than the other side, which takes most of the wear, and leaves behind a sharp edge consisting of the hard-surfacing. This can also be done by sputtering a metal like tungsten onto one side of the blade- yielding a so-called "self-sharpening* blade!

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  • $\begingroup$ Thanks for your reply. (Maybe dumb) question: If surfaces can be built up and replated, can that be done multiple times? I.e., can historic engines be kept running for centuries using these techniques? $\endgroup$
    – Justify
    May 12 at 1:51
  • $\begingroup$ Plating up a worn out crank or camshaft can double the useful lifetime of the part, but after the second teardown there might not be enough thickness left in the cylinder walls to support another reboring unless the engine was designed for truck use. This usually means the end of the engine unless it is exceptionally rare or valuable, so the replatability of the crank is not the deciding factor. $\endgroup$ May 12 at 4:47
  • $\begingroup$ I could have sworn I saw antique cars with engine repair sleeves. $\endgroup$
    – Justify
    May 12 at 13:15
  • $\begingroup$ @justify, some engines can be re-sleeved in this manner, or their cylinder pulled completely off and replaced with new (old air-cooled VW's), others cannot. $\endgroup$ May 12 at 18:37

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