Compound layer

When welding nitrided parts, you have to completely grind or mill off the case layer beforehand. The layer is glass-hard and brittle; if you weld on it, you'll get cracks or the weld won't hold. Best to remove it generously around the weld area. After that, you can weld normally, but the base material has changed its properties due to nitriding – you have to take that into account in joint preparation and heat control.