| Overlay Chemistry | Chromium, carbon, manganese, silicon, and iron balance in the deposited hardfacing layer. | Product specification, welding procedure, and agreed chemical analysis limits. No single universal chemistry applies to every chromium carbide overlay plate. | Optical emission spectroscopy, X-ray fluorescence, or an equivalent laboratory method performed on representative overlay samples. | Confirm that the chemistry matches the agreed grade and intended wear mechanism, especially abrasive wear and elevated-temperature service. | Heat or batch chemical report, sampling plan, and traceability records. |
| Carbide Microstructure | Distribution, morphology, continuity, and orientation of chromium-rich carbides within the iron-based matrix. | Metallographic acceptance criteria defined in the purchase specification or approved reference sample. | Cross-section preparation followed by optical microscopy or scanning electron microscopy. Image analysis may be used for carbide spacing and area fraction. | Look for a reasonably uniform carbide network without excessive segregation, porosity, unmelted particles, or abnormal cracking. | Metallographic report with etched micrographs, sample location, magnification, and evaluation date. |
| Hardness | Surface hardness of the overlay and, where relevant, hardness through the overlay thickness and in the base plate. | ASTM E18 for Rockwell testing, ASTM E384 or ISO 6507 for microhardness, depending on the approved method and material thickness. | Multiple hardness readings taken from cleaned, representative locations; indents should avoid visible cracks and edges. | Use the contract range rather than a generic number. Chromium carbide overlays commonly have very high hardness, but hardness alone does not predict service life. | Hardness map, test load, scale, number of readings, calibration status, and sampling location. |
| Abrasive Wear Resistance | Resistance to sliding or three-body abrasion under controlled conditions. | ASTM G65 dry sand/rubber wheel abrasion is widely used for comparative evaluation of hardfacing materials. | Measure mass loss or volume loss after exposure to specified abrasive, load, wheel condition, speed, and test duration. | Compare only results generated using the same ASTM G65 procedure, test severity, and reporting units. Lower mass or volume loss indicates better laboratory abrasion resistance. | Complete test report, specimen orientation, test procedure, abrasive details, raw mass data, and calibration records. |
| Impact and Gouging Performance | Ability of the overlay and substrate system to withstand impact, deformation, and localized gouging. | No single wear test represents every field condition; an application-specific qualification test is normally required. | Instrumented impact testing, laboratory gouging tests, or controlled field trials using representative impact energy and material feed conditions. | Prioritize a balanced overlay/substrate design. Extremely hard deposits can be unsuitable where repeated impact or severe bending dominates. | Application test protocol, failure photographs, impact energy, operating conditions, and performance comparison against the approved reference. |
| Crack Pattern | Presence, spacing, width, depth, and orientation of stress-relief cracks in the overlay. | Acceptance limits must be stated in the purchase specification because stress-relief cracking can be normal in many hardfacing products. | Visual inspection, dye penetrant testing where appropriate, dimensional measurement, and cross-sectional examination for crack depth. | Do not reject all cracks automatically. Reject cracks that exceed agreed limits, reach the substrate, form interconnected defects, or create unacceptable structural risk. | Inspection standard, crack map, photographs, crack-size limits, and disposition procedure for nonconforming areas. |
| Bond Integrity | Fusion between the hardfacing layer and base plate, including lack of fusion, delamination, and inclusions. | Acceptance criteria should be agreed before production; the applicable welding or surfacing procedure should define essential variables. | Metallographic cross-sections, ultrasonic testing where suitable, dye penetrant testing for surface-connected defects, and visual inspection. | Require continuous metallurgical bonding in critical areas and clearly defined limits for discontinuities, edge defects, and repair zones. | Cross-sectional records, NDT reports, welding procedure qualification, and repair documentation. |
| Dimensional Accuracy | Overall length, width, thickness, overlay thickness, flatness, squareness, and hole or cutout locations. | Approved drawings, tolerances in the purchase order, and agreed measurement procedures. | Calibrated steel rule, caliper, micrometer, laser measurement, straightedge, or coordinate measurement equipment as appropriate. | Specify whether dimensions are measured before or after cutting, forming, machining, or stress-relief distortion. | Dimensional inspection report, equipment calibration certificates, and marked-up inspection drawing. |
| Flatness and Distortion | Plate bow, twist, edge lift, and distortion caused by thermal deposition. | Project drawing or purchase specification; a universal flatness tolerance is not applicable to every plate format. | Straightedge and feeler gauge, surface table, laser scan, or other documented method over the specified measurement length. | Set limits based on installation method and whether the plate will be rolled, formed, bolted, or welded after delivery. | Flatness map, measurement grid, correction records, and final inspection approval. |
| Base Plate Quality | Base metal grade, thickness, lamination condition, weldability, and mechanical properties. | Material standard stated in the purchase order, such as the applicable carbon steel or alloy steel specification. | Mill test certificate review, thickness measurement, visual inspection, ultrasonic examination for laminations where required, and mechanical testing when specified. | Ensure the substrate is suitable for the intended welding, forming, temperature, and structural requirements rather than evaluating the overlay alone. | Mill certificate, heat number, chemical composition, mechanical properties, and supplementary NDT results. |
| Welding and Surfacing Procedure | Process, consumable classification, preheat, interpass temperature, travel speed, deposition sequence, and cooling control. | EN 14700 may be used for hardfacing welding consumables; qualification requirements should be defined by the project specification and applicable welding code. | Procedure review, qualification coupon testing, welder or operator qualification where applicable, and production parameter monitoring. | Require controlled essential variables and documented repair procedures. Verify that production practice matches the qualified procedure. | Welding procedure specification, qualification record, consumable certificates, parameter logs, and operator qualifications. |
| Temperature Capability | Retention of wear performance, dimensional stability, and bond integrity at the actual operating temperature. | Application-specific qualification is necessary; room-temperature hardness or abrasion data cannot establish high-temperature performance by itself. | Elevated-temperature hardness, thermal cycling, oxidation evaluation, and wear testing at the specified service temperature. | Confirm maximum continuous and intermittent temperature, atmosphere, thermal cycling frequency, and cooling conditions. | Temperature-specific test report, service limitations, and recommended operating envelope. |
| Cutting and Fabrication Suitability | Recommended cutting process, heat-affected zone, edge cracking, drilling method, and minimum bend radius. | Manufacturer’s fabrication procedure and project-specific fabrication requirements. | Trial cutting, edge inspection, bend trial where required, and dimensional verification after fabrication. | Confirm that the plate can be cut and installed using the buyer’s available equipment without damaging the substrate or overlay. | Cutting guide, forming limits, drilling recommendations, repair instructions, and fabrication test results. |
| Traceability and Quality System | Ability to trace finished plates to raw materials, welding consumables, production parameters, inspections, and shipment records. | ISO 9001 certification can support process control, but certification does not replace product-specific inspection requirements. | Document review and audit of heat numbers, batch records, inspection reports, nonconformance reports, and corrective actions. | Require full traceability for critical applications and verify that certificates correspond to the delivered plate identification. | Quality manual, certificate of conformity, batch record, inspection and test plan, and nonconformance history. |
| Application Fit | Compatibility with the dominant wear mode: sliding abrasion, impact, gouging, erosion, corrosion-assisted wear, or high temperature. | Engineering selection based on actual operating conditions rather than a single hardness or chromium percentage. | Review of particle size and hardness, impact energy, material flow, temperature, corrosion environment, plate support, and expected service life. | Select the product using field conditions and total cost of ownership, including installation, downtime, repairs, and replacement frequency. | Application references without confidential brand claims, wear-life data, design calculations, and service recommendations. |
| Commercial Evaluation | Price per usable area, lead time, minimum order quantity, packaging, warranty, replacement policy, and technical support. | Contract terms, inspection and test plan, agreed Incoterms, delivery schedule, and warranty conditions. | Supplier quotation comparison, sample approval, reference checks, pre-shipment inspection, and review of historical delivery performance. | Compare total delivered cost and expected service life rather than purchase price alone. | Formal quotation, delivery commitment, warranty terms, packing specification, technical datasheet, and after-sales procedure. |