Buffer layer
A buttering layer is the first weld layer that is welded not with the actual filler metal but with a softer, tougher additive. It absorbs stresses and prevents cracks between hard base material and hard cap layer.
Physical-Chemical Mechanism of Action
A buffer layer is a soft, tough layer that goes between the hard base material and the hard top layer. Because it can deform, it absorbs part of the and spreads it over the area instead of concentrating it at the . And it keeps dilution low: the hard filler from above doesn't hit the base material directly, which would harden immediately.
Metallurgical Relevance & Welding Risks
Without a buffer, a narrow, glass-hard strip forms at the fusion line, where stress and brittleness come together. That's where overlays pop off, and that's where start. You need this for repairs on tool steel, for , and for . Austenitic fillers or are used as buffer materials because they stay tough and can take stress.
Workshop Practice & Instructions
Buffer thin—one or two layers is enough. If you build up too much soft layer, you'll have a cushion under the hard top layer, and it'll sink under load. Run with low so less base material is melted in. Even with a buffer, and hold the interpass temperature. Clean between passes and grind out notches.