Tungsten hot hardness

Tungsten is what gives steel its hot hardness – the ability to stay hard and cutting-capable even under strong heat. It forms hard carbides that don't decompose quickly at high temperatures. But when welding such material, it also means: the more tungsten in it, the more brittle the material becomes. Too much of it and the part breaks under load instead of deforming. When welding, you must be careful not to over-harden the heat-affected zone and not to overheat the material, otherwise you'll get cracks.