Page 119 - SSAB Welding Handbook Edition 2

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Welding handbook 20.0 Hardfacing

4 Counteract crack propagation. Cracks often occur
in the hardfacing layer. A buffer layer can obstruct
©SSAB
cracks between the hardfacing layer and the parent
metal because it is ductile and it can introduce
compressive stresses in the hardfacing layer.

Hardox and Strenx steels are supplied with or
without primer painted surfaces. The buffer layer
can be welded directly on to either surface. When
the buffer layer is welded directly on to a primed
plate, apply the general information regarding Chromium Niobium Boron Martensite
welding on to primer specified in chapter 9. carbide carbide carbide (matrix)

Fig. 20.6: A hardfacing layer from a carbon rich consumable.
20.3 Characteristics of the Magnification ~ x 100.
hardfacing layer (Reproduced by permission, Castolin AB)

For the Hardox and Strenx grades, martensitic and
carbide rich consumables are the typical variants for When combinations of different types of wear are
the hardfacing layer. present in an application, the consumable for the
hardfacing layer is selected in order to suit each
wear type as closely as possible. If one wear type is
Martensitic consumables, as the name indicates, are
designed to achieve a martensitic microstructure dominant in relation to the others, select the
in the weld metal. This contributes to a very high consumable that provides a high resistance towards
hardness of the hardfacing. Martensitic consumables the principal wear type.
typically have favorable properties for use in abrasion
wear applications and can be a good alternative for The hardfacing layer should not be too thick.
preventing impact wear of solid bodies. Normally, the hardfacing layer has a thickness of
1 to 3 weld passes. Excessive thickness will promote
spalling of the hardfacing layer. For some types of
Carbide rich consumables exist in several variants.
They all contain carbides of high hardness that are hardfacing consumables, the manufacturer specifies
embedded in a surrounding substance called the a certain number of weld passes in the thickness
matrix. An example of this microstructure is shown direction to attain beneficial properties in the weld
in fig. 20.6. metal.

The characteristics and composition of the matrix
depend on the specific consumable. Typically, the
properties of this type of consumable provide a weld
metal with favorable resistance towards abrasion
and erosion wear. Carbide rich consumables with a
hard matrix are preferred for structures subjected
to erosion because they resist the wear caused by
the small individual particles. However, this type of
weld metal often has poor results in resisting impact
wear of solid bodies.

This handbook contains general suggestions and information without any expressed or implied warranty of any kind. SSAB hereby expressly disclaims
all liability of any kind, including any damages, in connection with the use of the information and for their suitability for individual applications. 119
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.