Throughout this article we will use the term CCO, which stands for Chrome Carbide Overlay plate.
CCO is made by machine welding hardfacing on a mild steel base plate.
Some people may have had difficulty using CCO.
Evaluating comments over many years, we see most issues can be traced back to 3 common installation mistakes.
Here we will review the three most common installation errors, and what you can do to prevent them from happening in your applications.
This photo shows two primary causes of CCO wear plate failure.
The RED ‘A’ shows how the joining weld has worn away. This is caused by not hardfacing a cap over the joining welds. This issue will result in a premature failure and unplanned downtime.
The YELLOW ‘B’ shows what happens when the edge of the CCO plate is exposed to the abrasive elements. The mild steel backing plate is not hard and will quickly wear away. Without the base for support, the carbide surface falls away; leaving no abrasion protection, results in premature failure and unplanned downtime.
This is the primary cause of most CCO failures. It is important to understand joining welds are NOT HARD LIKE THE OVERLAY surface. This means the weld joint does not have the same abrasion resistance as the CCO deposit. The abrasion material flow is now able to get behind the wear plate and create a hole through the equipment structure.
DO THIS for a successful installation:
After all welds have secured the wear plate, apply a hardfacing alloy to cover all joining welds. This will protect the joining weld deposit keeping your steel plates in position.
NEVER allow the edge of a CCO plate exposed to abrasive elements. The mild steel backing plate for the CCO deposit is not hard and wears away rapidly.
The Chrome Carbide Overlay is there only for wear resistance. This means the overlay has no structural integrity by itself. That is the overlay’s only job. When the softer mild steel base plate has worn away, there is no support for the overlay.
Like a violent flood causes a river bank to fail; the carbide surface will tumble into the abrasive flow. This leaves you with zero protection, resulting in another premature failure and unplanned downtime.
DO THIS for a successful installation: More critical than the weld joints, ALL exposed CCO plate edges MUST be covered by a compatible hardfacing alloy. Preferably the same deposit as the overlay; covering all edges of the CCO wear plate
It is important to remember the overlay has no structural strength by itself. If you are installing a ¾” thick CCO plate, this means the structural mild steel is 3/8” thick with another 3/8” of CCO deposit. As a result CCO cannot withstand being supported only by widely spaced support beams. Any flexing will result in failure of the mild steel base plate, leading to shear failure often seen as ‘chunking out’.
This piece of CCO was not adequately supported, allowing a large chunk to fall out of the plate.
DO THIS for a successful installation: Have any CCO plate fully supported underneath. The best prevention against flexing is to secure the plate using enough plug welds.
Starting from the center of the plate, weld the holes to secure the wear plate in an expanding outward circle. Have no distance greater than 18” between the plug welds or plate edges.
Use this chart to determine the proper size of your plug weld holes, based on the CCO thickness plate you are installing.
These plug weld holes were not capped, and the joining weld wore away; allowing the welds retaining the CCO plate to flex until it failed. This unplanned breakdown required extensive repairs.
Posted on 02/26/2020 at 04:23 PM
