Page 121 - SSAB Welding Handbook Edition 2

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Welding handbook 20.0 Hardfacing

Relief cracks Underbead cracks
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Relief cracks are rather frequent occurrences in An underbead crack is a kind of hydrogen crack that
hardfacing layers. Other names for this sort of crack can form in the parent metal during a hardfacing
are transverse crack and cross crack. This kind of procedure. If underbead cracks occur, they are located
crack is oriented transverse to the direction of the in the parent metal beneath the hardfacing layers, see
weld metal as the two latter names indicate. fig. 20.9. The risk for underbead cracks is minimized
by following the welding recommendations presented
Commonly, the consumable for the hardfacing in this chapter.
layer is designed to form relief cracks in order to
lower the residual stresses in the welded area,
according to fig. 20.8. This increases the resistance
of the hardfacing layer to spalling from the parent
metal and decreases the residual stresses in the
joint caused by the hardfacing layer. The wear Fig. 20.9: Underbead cracks in the parent metal. The buffer layer is
resistance is not substantially reduced due to this left out in this situation.
type of crack. As is earlier mentioned, the buffer
layer counteracts potential crack propagation from
the hardfacing layer into the parent metal.

Fig. 20.8: Transverse cracks in a hardfacing layer.

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