| CCO Plate Definition | Chromium Carbide Overlay plate consisting of a carbon-steel or low-alloy steel backing plate with a wear-resistant chromium-rich hardfacing layer. | Confirm that the product is a welded overlay plate rather than homogeneous high-chromium cast plate or quenched-and-tempered wear steel. | Provides high resistance to abrasive wear while retaining a weldable and structurally supportive steel backing. |
| Backing Plate Material | Commonly mild carbon steel or low-alloy structural steel; typical carbon content is approximately 0.15–0.30%, depending on the backing grade. | Request the mill certificate, chemical composition, yield strength, tensile strength, and impact-test data where required. | The backing controls plate support, formability, weldability, and resistance to impact loading. |
| Overlay Chemistry | Typical hardfacing chemistry contains approximately 15–30% chromium and 2–6% carbon, with iron as the balance; manganese, silicon, molybdenum, niobium, or other alloying additions may be used. | Compare the actual deposited chemistry rather than relying only on a product grade name. Ask whether the analysis is taken from the weld deposit or supplied wire. | Chromium and carbon promote chromium-carbide formation, which determines abrasive-wear resistance and hardness. |
| Primary Carbide Phase | Predominantly chromium-rich M7C3 carbides dispersed in an iron-based matrix. | Review metallographic photographs or test reports for carbide distribution, dilution, porosity, cracks, and excessive segregation. | Uniform carbide distribution generally improves consistency of wear life across the plate surface. |
| Overlay Hardness | Usually about 55–65 HRC, commonly equivalent to approximately 550–800 HV, depending on alloy design and test method. | Confirm the hardness scale, test load, measurement location, number of readings, and whether values represent the first layer or final surface. | Higher hardness usually improves resistance to cutting and gouging abrasion, but can reduce forming and machining capability. |
| Backing Plate Thickness | Commonly approximately 4–40 mm, with special sizes available for engineered applications. | Check thickness tolerance, flatness, minimum usable backing thickness, and whether the plate can be cut without damaging the overlay. | Thicker backing plates provide greater structural stiffness and impact support. |
| Overlay Thickness | Commonly approximately 3–30 mm; many general-purpose products use a 4–12 mm overlay. | Specify nominal thickness, local minimum thickness, tolerance, number of deposited layers, and allowable surface waviness. | Overlay thickness affects service life, component weight, repair frequency, and total installed cost. |
| Plate Size | Frequently supplied in formats around 1,500–2,100 mm wide and 3,000–4,000 mm long, subject to production capability and transport limits. | Confirm maximum shipping dimensions, usable cutting area, edge zones, and dimensional tolerances before placing an order. | Available dimensions influence nesting efficiency, material waste, and fabrication time. |
| Overlay Process | Open-arc welding and submerged-arc welding are widely used; automated multi-pass deposition is common for repeatable plate production. | Ask for welding process details, current and voltage ranges, travel speed, interpass temperature, and deposition sequence. | Process stability affects dilution, carbide morphology, surface consistency, residual stress, and crack pattern. |
| Weld Surface Pattern | Parallel or overlapping weld beads are normal. Stress-relief transverse and longitudinal cracks may occur in many high-chromium overlays. | Verify the specified crack width, spacing, orientation, bead overlap, and acceptance criteria. Cracks should not extend through the backing plate. | Controlled stress-relief cracking can reduce residual stress without necessarily indicating product failure; through-cracks can compromise structural integrity. |
| Dilution Control | The chemical composition of the first overlay layer is affected by mixing with the backing steel; additional layers normally provide chemistry closer to the intended hardfacing alloy. | Request dilution information or cross-sectional test results, especially for thin overlays and high-wear applications. | Excessive dilution can lower hardness and reduce the volume fraction of chromium carbides. |
| Abrasion Resistance | High performance against mineral, sand, coal, clinker, cement, and other sliding or low-to-moderate impact abrasives. | Match the plate to the actual wear mechanism: sliding abrasion, gouging abrasion, impact, erosion, or a combination. | CCO plates are particularly effective where abrasive particles remove material by cutting, ploughing, or scratching. |
| Impact Capability | Moderate impact resistance; generally lower than that of tough quenched-and-tempered wear steels or austenitic impact-resistant alloys. | For heavy impact, large-particle loading, or repeated shock, request application references and impact-test evidence. | Very high impact can fracture the brittle carbide-rich overlay or accelerate spalling. |
| Temperature Capability | Often suitable for dry service at approximately 500–600°C, but the practical limit depends on alloy chemistry, load, oxidation, and thermal cycling. | Obtain a temperature limit for the specific deposited alloy and verify performance under continuous versus intermittent heating. | Elevated temperature can soften the matrix, oxidize the surface, and change carbide-matrix behavior. |
| Forming and Bending | Cold forming is limited and application-dependent. Bending should normally be performed with the overlay on the outside only when the supplier provides a minimum radius. | Confirm minimum inside radius, bending direction, preheating requirements, and whether forming is permitted across weld beads. | Incorrect forming can cause overlay delamination, excessive cracking, or backing-plate distortion. |
| Cutting Method | Plasma cutting, abrasive waterjet, and oxy-fuel cutting are commonly used; the overlay side may require slower cutting or additional consumables. | Define heat-affected-zone limits, edge hardness requirements, kerf allowance, and post-cut edge treatment. | Cutting quality affects dimensional accuracy, weld preparation, and the risk of edge cracking. |
| Machining and Drilling | The hardfacing surface is generally not conventionally machinable; grinding, abrasive waterjet, carbide tools, or specialized drilling methods may be required. | Plan holes and precision surfaces before overlay deposition where possible. Confirm recommended tooling and drilling parameters. | Fabrication method has a major effect on installation cost and lead time. |
| Welding to Backing Plate | Structural attachment is normally made through the backing steel using compatible low-hydrogen procedures; welding directly onto the overlay requires specialized consumables. | Request a qualified welding procedure, preheat and interpass limits, consumable classification, and hydrogen-control requirements. | Correct welding prevents hydrogen cracking, excessive dilution, and loss of structural capacity. |
| Surface Quality | Typical surface includes overlapping beads, minor waviness, localized spatter, and controlled stress-relief cracks. | Specify acceptable bead height variation, surface waviness, edge condition, spatter removal, and repair policy. | Surface uniformity supports predictable wear and simplifies fitting, lining, and replacement work. |
| Inspection and Testing | Common checks include visual inspection, dimensional inspection, hardness mapping, chemical analysis, metallography, and ultrasonic testing of the backing plate where specified. | Agree on sampling frequency, test locations, calibration requirements, documentation, and nonconformance handling before production. | Documented inspection reduces variability between batches and supports traceability for global projects. |
| Typical Applications | Chutes, hoppers, feeders, conveyor transfer points, crusher components, screens, pipe bends, fan blades, mixer liners, and cement or mining equipment. | Provide particle size, material hardness, impact level, operating temperature, sliding speed, and expected service hours. | Application data is essential because no single CCO formulation is optimal for every wear mechanism. |
| Buyer Documentation | Recommended documentation includes technical datasheet, material certificate, overlay chemistry, hardness report, dimensional report, welding procedure, inspection plan, and packing record. | Require heat or batch traceability from raw backing plate through overlay production and final inspection. | Complete records support quality claims, customs clearance, maintenance planning, and replacement matching. |
| Total Cost Factors | Total delivered cost includes plate price, overlay thickness, cutting yield, freight, packaging, fabrication, tooling, installation, and expected service interval. | Compare cost per operating hour or cost per ton of handled material rather than purchase price alone. | A thicker or higher-alloy overlay may cost more initially but reduce shutdowns and replacement labor. |
