Cobalt

Prevents carbide coagulation at high temperatures and increases high-temperature strength in high-alloy hot-work and high-speed steels.

Cobalt keeps the carbides finely distributed; otherwise they'd clump together at high heat and the steel would lose its hot strength. When welding, that means you have to control the heat cleanly and not cool too fast, or you'll get porosity or cracks. If the steel has cobalt, it handles heat better and the part lasts longer. So: clean cooling, no jerky torch action.

MetallurgieSchweißtechnik