Why are there cracks in our hard faced plates and why are they not damaging to quality?

I’m often asked why there are cracks in our wear plates and whether these don’t lead to faster wear. Today I would like to try to explain why the cracks appear and why they are not a disadvantage.

Whenever we notice cracks in a solid material – whether in metal, wood, stone or glass – these usually lead to a loss of strength or even breakage. Therefore, it would be logical to assume that cracks in our wear layers are also detrimental. In fact, it’s exactly the other way around: cracks are not only advantageous, but also represent a clear sign of quality.

Cracks in the build-up weld metal depend primarily on the alloy. When it comes to our hard faced wear plates, we only talk about coatings with Fe-C-Cr alloys which have no elasticity, similar to hard chrome cast iron. During cooling from the molten state, the resulting shrinkage stresses try to dissipate.

In order to prevent detachment from the elastic carrier material, more or less regular transverse cracks form in the direction of the hard facing. If the shrinkage stresses were not reduced in this way, entire parts of the hard facing would detach from the carrier sheet.

As long as the cracks are finely distributed and thin, they do not pose a problem for wear protection. On the contrary, one can even say: “The more cracks, the better stress reduction, the better for the durability of the connection between the base material and the wear layer”.

It is important to note that the cracks are only in the wear layer. The carrier material – which determines the strength of the component – is not damaged if processed correctly.

The attached picture shows the finely distributed relaxation cracks transverse to the welding direction.

DURAPARTS and its partner companies have been providing individual wear protection solutions in German-speaking countries for many years.