Tungsten carbide (hardmetal coating)

Tungsten carbide is a composite material made of extremely hard tungsten carbide grains embedded in a tougher metal matrix. That makes it super wear-resistant, but also tricky to weld. When you weld it, you heat it up strongly, and the bond between the grains and the matrix can break – the part becomes brittle and can crack or splinter. You have to keep the heat input low and be careful not to melt too much base material. In practice, that means short welding intervals, let it cool well between passes, and don't put unnecessary heat into the part. If you follow that, you get a durable joint without the carbide losing its hardness.