11:25 Oct-28-2009 anjafo NDT Inspector Norway, Joined Aug 2009 204
ndt of cladding
I have some experience with this. Usually the cladding has been used to build up a seal face before machining.
After machining we perform MPI or DPI checking for defects. Here we almost always find indications in the bond/fusion area between parent material and new cladding material. Both methods show indications. Usually a light machining will remove the indication but generally as its a seal area and been machined down this is not welcome by customer. You can actually see the fused line very well after machining.
Does anyone have experience on what is causing these indications?
Its an expensive process, welding, machining, checking etc so its difficult to just tell customers there is an rejectable indication and leave. Also difficult to leave indications in the item unidentified.
I have also done UT to check fusion between parent and weld materials sometimes but the item needs to be correct geometry for this.
I know wall thickness can be checked by different methods also.
Were I used to work, we did this on Steam Generators tube sheets. We did sometimes have problems and it was always related to the welding process. But we didn't experience the type of defect that you are experiencing. I suggest maybe to have your welding engineer review the procedure and change some of the parameters such a rate of deposit and your amperage.