Friction welding is a well understood & used industrial process - the cars & busses you travel around in have the wheel attachment flange friction welded to the stub axles for at least the last 60 or so years, Caterpillar have used it to make the connections between different sized components in the drive trains of their heavy machinery. But, yes, you do have to check the results carefully, and any fault mean the whole thing is scrapped, there is no going back & having another go.

On a related note, there was an interesting engine incident on a high tech helicopter in Australia a year of two ago - helicopter was being trialed for Oz Defence forces & one of the service pilots was very critical of the new machine compared to the existing product during early trials. Some time time later he was flying the machine over the outback (I beleive Brisbane to Adelaide) when he got the flashing lights & buzzers from one engine. He killed the engine, pushed the remaining engine to full power & completed the flight without further trouble. He became a rabid supporter of the new machine & told the in service enquiry that anything else in use with the same problem would have been an immediate controlled crash landing. I can't name names or models.