Build-up weld on cast iron?

One machine I regularly repair uses cast iron arms to hold a mixing bowl. The bowls' mounting tabs are stainless and over time "cut" away the cast iron.
If the wear is minimal then a re-milling of the arms works. The problem is when the wear gets about 1/8"+. Over 1/8 then problems arise, position, height in machine, etc.. The area affected is approx 3.5" long x 2.0" wide.The arms are thick cast (5/8 min)
Have considered welding with nickel rod and re- milling the surface. Is there a better rod to use? The finish must remain looking like cast iron, so no brazing, etc.
Is welding an option for this repair?
My only other option is to make matching stainless plates to attach to the cast iron arms. There are some mounting issues adding plates so welding was/is my first choice. What do you think?

Hi there Andy.

MMMMMMMMMMMMM tricky one you got there, In my experience, welding CI especially in applications like that can give you a whole more trouble than any man needs on a good day, let alone a bad one.

If and it's quite a big IF you get away with building it up with weld, taking in to account the pre heat and post weld cooling,etc tecec, then theres still every chance it's gonna be harder than whores heart, and a right pig to machine.

So thinking about it I'd go for the machining option, the mounting issue one over come is there for good and will make maintenance / replacement easier,........you say it's an on-going job.

The next thing that concerns me a bit, and please don't take this the wrong way, I'm not trying to rain on your parade, more my thoughts.

Stainless against stainless ain't too good, as it tends to gall and scuff up,....... which set me thinking:- as the arms are cast iron ie, and ferrous therefore will rust if they want, is there any reason why you can't use a carbon / mild steel?........ I know that over here we have issues with old machinery and new parts etc, seeing as the worlds gone bloody stainless crazy.

Another thought, could the holder blocks be made out of nylon or some such? or maybe stainless steel holders with say an easily replacable nylon insert.

Or another could you make the replacement parts from CI? bolt on or whatever, same as before?.

Hope something of this may be of help, take care.Sami.

I don't think you'll find a better rod than nickel. Especially since you have to machine it. Is it maleable cast iron? Could you make a plate and fasten it on with flat head screws?

This fellow would probably know: http://www.georgemillermachine.com/

Check the manifold repair!

The unit is in the food industry so the cast is painted, of course it wears off the attachment point. I don't know if it is maleable or not. I don't really know the difference.
Limy: I understand your points, maybe a plate is the way to go. As long as I get a good fit ,can't have food getting between the plates as it will grow and seperate the two, hence the reason for welding/milling. steel is out, rusting.
How tough is nickel to mill, will HSS cut it. I use a horiz mill with a 8" stagger tooth to mill these arms now.

Andy

Nickel rod is tough and stringy. Puts a lot of strain on the cutting tool. Sounds like you have the machine for it. Rigid setup and strong tool edges are called for. Lots of coolant to flush away chips. HSS should be OK. I've had mixed success. Better success was had with carbide but I didn't get the chips flushed out and ruined a couple of edges. Also the weld can pick up carbon from the base metal which make hard spots. Put down a thin layer real cold and fast to minimize admixture.

Arc welds with nickel rod will shrink up the cast iron like crazy. If you can weld on both sides of the part to balance the forces and the part can stand the shrinkage the it's OK. If not, like Sami said, a world of trouble.

I can't say enough good about flame spray with nickel filler and a powder torch. Less shrinkage, natural preheat and very little admixture. The build-up is easier to control so I rarely need to mill which is good because the deposit is tough!

Bud

Could you use cast iron rod, fill and then machine? It machines easily but of course you have only returned the machine to spec and the initial problem will continue. Of course in business we call this an income stream.

That's a good thing my professor told me...

Andy, your point about bio growth inbetween the two parts if you bolted it up, how about an epoxy or silicone gasket type sealing compound between the mating faces?

Just a a thought,

Take care. Sami.

Chris
Cast rod sounds good. it takes years to wear so repeat work won't be much.
Sami
Something would have to be put between parts. The disadvantage of a plate is the time/cost to have/make one since it is shaped like a kidney and two holes must be dead-on.
Let me start with cast rod, I'll give an update, pictures, if I can get my camera software working.
Thanks for the suggestions so far.