I'm old school and prefer NiRod for repair of cast iron anything if ascetics are not an issue. Its high nickel content (55%) provides a similar coefficient of expansion rate and strength (55-60 kips) eliminating harmful stress due to temperature cycling. However, brazing, with the right filler material is also very durable. Grade IV or V (silver braze) brazing rod is my preference due to its elevated melting temperature and higher strength, at least for grade IV. Prepping parent metal, cleanliness, preheat of parent metal, correct flux and controlled post braze cooling is key to successfully joining dissimilar metals for trouble free service. The only drawback is the unsightly dissimilar color of the repair. If it was my header, I'd go with spray welding. GE developed the process sometime in the 40's or 50's and it was limited to repair of shafts and coating of materials subject to high abrasion, corrosion and high temperature applications. I employed the GE Apparatus Shop in the 60's & 70's to use the process for a number of prototype applications, which proved to be very successful regarding longevity and cost reduction. It's good to know the process has been expanded to include repair of castings; I learned something else today, LOL-Oliver
