Jason,
It's good to here that someone else is welding PM material. I posted on this subject a few months ago and received no response. We weld a great deal of PM material, both CS, and SS. Most of our applications are CS PM welded to ferritec SS, and SS PM welded to austenitic SS. We did some development of FS-200 welded to 1018 using 70S-6, and 80S-2 wire. They produced sound welds, but some fatigue testing showed a considerable hardness along the HAZ of the PM base metal. Proceed with caution on the CS if the parts have any post sintering machining work on them. Our development has shown that the porous nature of PM holds vast amounts of cutting fluid in them if they are not processed properly for welding from the sintering plant. We have actually had parts that looked and felt clean, but once heated to 200F, the oils started oozing out from pores in the base metal. In order to make the parts weldable, the manufacture now performs a secondary inert gas oven bake of the parts after all machining is complete. I don't know your application, but with proper development, welding PM is a good option. PM is much more cost effective than that of fine blanked counterparts.
Mark
Hello Jason and Mark, I dabbled a bit in doing some repair work with some broken PM parts before. As I recall these parts were CS and I ended up welding them with ER70-S2. I did run into some issues with oils that had soaked into the parts due to their service. As I initially started welding on them contaminants started boiling out and caused pinholing in the beads. I stopped and reground the parts, did some preheating on them, brushing the carbon deposits that resulted, preheated them again and brushed them again, and kept this regimen up until I no longer saw any oils leaching out of the parts. Once they came up clean and I had brushed all of the carbon deposits off they welded up really nicely. I realize this is slightly different from the scenario that you are describing, but providing you are not having to deal with contaminants I don't feel the welding will be anything excessively out of the ordinary. As Mark stated, cleanliness will likely be the key to your successful fabrication with these materials. Please forgive me Mark, I should have read your post more closely before posting my comments, you definitely covered the bases as far as prep and testing go. Regards, aevald
aevald,
I agree with preheating when it's in a reapir type of application, that's the only way to get the oils out of PM. During some of the testing I did in the early stages, I put a PM part in a vise and heated it up. When the oils started to come out I pulled the torch away and I had hundreds of little blue flames where the oil was coming out of the pores in the metal, it was a really neat sight! Needless to say, that's when we went back to the mill and asked what other manufacturing options they had to remove the oils before we try to weld them.
Hello Mark, you've jogged my memory now and I seem to remember a similar happening with the burning thing, kind of impressive to say the least. Regards, Allan
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