Tungsten carbide components in chemical and petrochemical equipment may face abrasive particles, corrosive media, temperature changes, and repeated mechanical loading. Selecting a suitable grade requires consideration of these conditions together.
Hardness alone is not enough. WC grain size, binder composition, binder content, manufacturing quality, and component design must support both wear resistance and reliable operation in the intended environment.
1. Start with the Process Chemistry
Cemented tungsten carbide consists of hard tungsten carbide (WC) grains held together by a metallic binder, commonly cobalt, nickel, or an alloyed binder system. Chemical exposure can affect the binder, the carbide phase, or both.
In some aqueous environments, preferential binder corrosion weakens the surface and allows carbide grains to detach more easily during wear. Strongly alkaline media can also attack the WC phase. These mechanisms depend on the specific chemical environment; pH alone cannot establish compatibility, and aqueous pH guidance should not be applied directly to nonaqueous process fluids.
Before selecting a grade, document:
- Fluid composition, concentrations, and water content
- Normal and maximum operating temperatures and pressures
- pH, where meaningful for the process fluid
- Chlorides, dissolved gases, oxidizing constituents, and other potentially reactive substances
- Cleaning chemicals, concentrations, temperatures, and exposure durations
- Changes during startup, shutdown, flushing, or process upsets
A grade suitable for normal operation may require further assessment if cleaning or upset conditions introduce different chemical exposures.
2. Compare Complete Grades, Not Just Binder Names
WC-Co grades offer a useful balance of hardness, wear resistance, and toughness. Where corrosion is a concern, nickel-based or other corrosion-resistant alloyed binder systems may perform better than conventional cobalt-only binders. Their suitability still depends on the process medium and the complete grade formulation.
Nickel-bonded carbide should therefore be treated as a candidate for evaluation, rather than an automatic solution. A change in binder system also requires a review of the grade's mechanical and thermal properties.
Compare candidate grades using:
- Binder chemistry and content
- WC grain size and microstructural consistency
- Hardness, fracture toughness, and strength data, with the test methods identified
- Relevant corrosion and wear results
- Experience in comparable service
Supplier designations such as YG and YN do not, by themselves, establish chemical compatibility or equivalence between suppliers. Compare documented properties and compositions rather than grade names alone.
3. Balance Grain Size and Binder Content
Within otherwise comparable WC-based grades, finer WC grains and lower binder contents generally increase hardness and resistance to certain forms of abrasion. Higher binder contents and coarser grains often improve fracture toughness, but may reduce hardness. These are general trends, not universal rankings across different binder systems and manufacturing routes.
The best balance depends on the damage mechanism. Fine-particle abrasion, high-velocity particle impact, sliding contact, and intermittent mechanical impact do not necessarily favor the same grade.
Reducing binder content is not a substitute for selecting a chemically suitable binder. Likewise, a tougher grade will not compensate for severe binder corrosion. Compare hardness values measured on the same scale and under comparable test conditions; transverse rupture strength and fracture toughness describe different properties and should not be treated as interchangeable.
4. Assess Corrosion and Particle Wear Together
Catalyst fines, sand, coke particles, and other solids can introduce erosion or abrasion alongside chemical exposure. Corrosion can undermine the binder supporting the carbide grains, while mechanical wear can expose fresh material to the process fluid. Static corrosion resistance alone therefore does not establish resistance to combined erosion-corrosion.
For applications involving solids, record particle composition, hardness, size distribution, shape, and concentration, together with local flow velocity and likely impact angles and locations. Identify whether damage occurs in a flowing slurry, at a sliding interface, or at a localized flow restriction.
Where combined wear is significant, use representative testing or documented experience under comparable conditions to support grade selection. A result obtained in one slurry chemistry or flow regime should not be assumed to apply to another.
If pumps, valves, or restrictions show localized pitting, investigate cavitation as well as particle erosion and corrosion. Cavitation involves bubble formation and collapse and may require changes to operating conditions or flow design in addition to material selection.
5. Include Temperature and Thermal Cycling
Review normal operating temperatures, maximum excursions, and the rate and frequency of temperature changes during cleaning, startup, shutdown, and process upsets.
Temperature can alter corrosion behavior and material properties. Rapid temperature changes can also create thermal stresses, while differences in thermal expansion between carbide and surrounding materials can change assembly stresses and fits. Room-temperature hardness should not be treated as a service-temperature rating.
For demanding thermal conditions, obtain grade-specific information and review the complete component arrangement, including support, fit, mating materials, and any relevant dry-running or loss-of-cooling conditions.
6. Match the Grade to Mechanical Loading and Component Function
Valve seats, seal rings, sleeves, bushings, and nozzle inserts experience different loading conditions. Grade selection should reflect the component's actual function, geometry, and support.
Assess:
- Contact, sealing, and differential-pressure loads
- Impact, vibration, and repeated loading
- Alignment, clearances, and component support
- Edge geometry, wall thickness, and local stress concentrations
- Mating materials, lubrication, and cooling where relevant
- Assembly and removal procedures
Hardness and toughness must be considered together. Selecting a harder grade without reviewing loading and geometry can increase the risk of chipping or fracture.
For seal rings and other precision contact components, surface finish, flatness where specified, and the mating material are also part of the assessment. Handling damage, uneven support, or inappropriate assembly forces can compromise an otherwise suitable component.
7. Use Evidence Relevant to the Application
Material selection should draw on supplier data, documented service history, inspection of returned parts, and representative testing. Review manufacturing quality alongside nominal composition, including porosity, microstructural defects, and the condition of finished working surfaces.
For unfamiliar or demanding chemical environments, exposure testing may help compare candidate grades. Where solids are present, combined erosion-corrosion or abrasion-corrosion testing may also be needed.
Test conditions should reflect the important features of the application, including chemistry, temperature, exposure duration, solids, and fluid movement. Evaluate surface damage and dimensional change as well as mass loss, where appropriate. Electrochemical measurements can support the assessment, but should not be used alone to predict component service life.
Laboratory results help compare candidates under defined conditions; they do not directly guarantee field life. Where practical, use a controlled service trial with agreed inspection criteria before broader implementation.
Where product purity matters, include limits on metal release or wear-particle contamination in the assessment.
Information to Include in a Grade-Selection Request
Provide the following wherever available:
- Equipment type and component function
- Process fluid composition, including cleaning and upset exposures
- Operating temperatures, pressures, flow conditions, and duty cycle
- Solids content and particle characteristics
- Current material or carbide grade
- Observed wear, corrosion, pitting, chipping, or cracking, including its location
- Service history, maintenance intervals, and the reason for replacement
- Drawings, tolerances, surface-finish requirements, and photographs
- Details of mating components, support, fit, and installation
- Estimated quantity and any process-purity requirements
For replacement parts, distinguish original drawing dimensions from measurements taken from worn surfaces. Photographs of both the damaged component and its installed position can help explain the service conditions.
EnduraCarbide's Application Support
EnduraCarbide Solutions manufactures custom tungsten carbide components from drawings or samples. We help review candidate carbide grades and binder systems according to the process chemistry, abrasive content, temperature, and mechanical loads, with dimensions, tolerances, and surface finishes tailored to the application.
For unfamiliar chemical exposures, grade selection may require additional compatibility data or application-specific testing.
Send your drawing or sample details for an application review and quotation.