What are the differences between Hardfacing, Chromium Carbide Overlay (CCO), Hardfaced Wear Plate?
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Even though they have similar names, chromium carbide hardfaced wear plates come in varying levels of quality depending on the method of production and the quality of raw materials!
Hardfaced wear plate products can be called different names including Chromium Carbide Wear Plate, Chromium Carbide Overlay (CCO) plate, Chrome Carbide Hardfaced, and Hardfaced Wear Plate.
Hardness is not the best metric for determining the quality or wear life of hardfaced wear plates!
The most important factors to consider when selecting hardfaced wear plates are:
(1) the production method
(2) the distribution of metal carbide (MC)
(3) the chemical composition and quality of the raw material
(1) Production Method
Hardfaced wear plates that are manufactured by bulk welding process exhibit a much more superior quality in comparison to those that are manufactured by flux cored wire. Bulk welding process enables the manufacturer to control the underlying
chemical composition of the wear plates by varying degrees as well as allow for the optimal dilution between the hardfaced weld layer and the base metal layer.
Figure 1 shows an example of a hardfaced wear plate manufactured by flux cored wire exhibit uneven and rough surface as well as large gaps between the weld beads. The roughness of the surface will ultimately affect the life time of the wear plate.
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Figure 2 shows a prime example of a premium quality hardfaced wear plate manufactured by bulk welding process; the surface is relatively smooth, with even welding along the length/width of the plate.
(2) Chromium Carbide Distribution (microstructure analysis)
Unlike the conventional quenched and tempered wear resistant plates, the abrasion resistant value of hardfaced wear plates cannot be measured from hardness testing alone. For example, a typical martensitic steel plate can have the equivalent hardness compare to hardfaced wear plates, but the abrasion resistant qualities are incomparable.
(http://www.hardfacetechnologies.com/postle_hft_btsp/pdfs/frequently_asked_questions_about_hardfacing1.pdf)
The abrasion resistant level for hardfaced wear plates can be determined by the percentage of chromium (%) in the overall chemical composition. The relationship between chromium and carbon percentage to the weight loss from abrasion testing (ASTM G65) can be seen in Table 1. (http://www.superiorconsumables.com/chrome-carbide-overlay-plate/)
The chromium carbide overlay is applied to a carbon steel base plate using an automated seam welder. Now, multiple layers of overlay can be applied to one base plate as long as the thickness of the overlay does not exceed the thickness of the baseplate being used. This process generates our stock overlay plate which is typically sold in 48” x 120” sheets. Larger widths are available, upon request, up to a maximum of 90 inches. For smaller parts, or for leading edges, the same overlay can be applied by hand using a MIG or stick motor application.
The surface cracks are a normal occurrence. They are stress relief cracks that occur as the plate shrinks as it cools. The cracks do not travel into the base plate, and therefore do not compromise the integrity of the material. As you can see from the top left photo, the base plate has no cracks and is not compromised in any way.
It is secure. The overlay process causes the overlay to fuse to the baseplate to prevent it from peeling away. This end process gives us our desired nominal thickness.
This is how we measure the total thickness of a finished Clif-Clad plate, with an overall tolerance of + or – 1/16 of an inch.
For example, a 1/2″ nominal plate is typically a 1/4″ overlay applied to a 1/4″ of base plate. The end result will be a plate that ranges between 7/16″ and 9/16″ thick, hence 1/2″ nominal thickness.
Clif-Clad is not difficult to work with so long as the proper procedures are followed. When cutting Clif-Clad, only plasma or waterjet must be used. The material cannot be flame, laser, or saw cut. Due to the extreme hardness, it cannot be drilled or CNC machined, but it can be Blanchard ground.
It is chiefly used as a liner material, the overlay itself however, has no structural integrity. It can be used in fabrications on it’s won, for example in formed pipes, but any welds or seams that require structural integrity must be adhered to the base plate and not the overlay itself.
Any areas which receive excessive wear or impact. Clif-Clad can increase the life of these components by 3-5x in many applications. Between CC and AR plate, if structural integrity is not a factor, I would choose the overlay Clif-Clad 100% of the time for the increased life expectancy it would give your material components.