Gents

I am new to this forum, and have been out of the general machine shop industry for some 12 years. Back then it was generally accepted that Arc spray was a superior form of depositing a layer on a undersize/worn bearing journal/seat.

There were flame spray units utilising wire & powder but they didnt seem to give the same bond strength, and were prone to cracking.

Could you advise what is considered the most effective spraying process today for building undersize/worn bearing journals.

Cheers

Dan

Hi Dan

to the Surface engineering forum.

The various thermal spray processes all have their own specific strengths and limitations. A bit like analogizing to our choice of transport method. Say a typical family car compared to an F1 racing car. You would not find your family car very effective in a Grand Prix race, nor would you find the F1 car effective for doing your weekly shopping.

If I were forced to generalize, I think I would still consider the old flame spray processes to be the most effective for the general machine shop industry. Mainly due to the economic/performance balance.

Arc, plasma, HVOF, cold spray processes may generally be capable respectively of producing coatings that are much denser, stronger and cleaner etc...which expands the capabilities of thermal spray, but not necessarily making the older technologies redundant, nor any less superior at what they do well.

Quote:Back then it was generally accepted that Arc spray was a superior form of depositing a layer on a undersize/worn bearing journal/seat.

I would agree with that opinion if you were to stick with a limited range of coatings and all your parts were of a geometry and size that suited arc spray. Perhaps not, if say you wanted molybdenum coatings (combustion wire spray molybdenum is in a class of its own) or more exotic coatings that can only be produced using powder.

Quote:There were flame spray units utilising wire & powder but they didnt seem to give the same bond strength, and were prone to cracking.

Arc spray does tend to give higher bond strengths, but I think the ?prone to cracking? comment could apply to all processes if not carried out properly.

At the end of the day you need to look at what the coating needs to do and at what cost, to decide which coating/process to employ. A good thermal spray job shop should have most of the processes available. One particular process can not produce the best of everything.

Dear Gordon,

Well said! As a manufacturer of all these process, with the responsibility to answer questions like this often, I have never said it better. Like you, I tend to be a flame wire guy, but mostly for corrosion coatings. For "hard wire" coatings, I tend to lean towards arc.

The answer, most of the time when asked which process is better, is "it depends on what you are doing."

Regards,

Jim Weber

Dear Jim,

What type of wire to you generally spray for corrosion coating?

Thanks

Danns