Ceramic Powder Suppliers

Industry Knowledge Expansion

How Particle Size Distribution Changes the Result When Spraying Ceramic Powder

Particle size is often specified by a single range, but the actual distribution (D10, D50, D90) decides whether a Ceramic Powder melts evenly, feeds smoothly and forms a dense coating. Fines below 10 µm tend to overheat, vaporize or clog the feed line through static cling, while oversized particles stay partially unmelted and leave pores and weak inter-splat bonding. Each process therefore needs its own window, and using a laser cladding grade in a plasma gun, or the reverse, is one of the most common causes of unexplained coating failure.

When we classify powder at Jiangsu Crystal Additive Manufacturing, we can tighten the cut to the window your equipment needs, because a narrow distribution usually matters more than the nominal range printed on the label.

Storage and Drying Practice for Oxide Ceramic Powder

Oxide Ceramic Powder such as alumina, titania, chromia and yttria-stabilized zirconia has a large specific surface area and readily adsorbs moisture from ambient air. Damp powder agglomerates, flows unevenly in the feeder and can cause pulsing in the plasma plume or spitting in the laser melt pool, which shows up as porosity and surface roughness. This is a handling problem rather than a material defect, and it is easy to prevent with a simple routine.

Recommended Routine

• Keep opened containers sealed with desiccant, and store them at relative humidity below 40%.
• Dry powder in a shallow layer (under 2 cm) at 120–150 °C for 2–4 hours before use, then let it cool in a desiccator.
• Avoid drying agglomerated powder that has already caked; sieve it after drying instead of forcing it through the feeder.
• Record the Hall flow time before and after drying, so a drift in flowability can be traced back to moisture rather than to the batch.

Matching Ceramic Alloy Powder to the Service Temperature

Ceramic Alloy Powder, usually a hard ceramic phase bonded by a metallic matrix (also called cermet), is chosen mainly by temperature and corrosion environment. Tungsten carbide grades deliver excellent sliding and abrasive wear resistance, but the carbide begins to decarburize and oxidize noticeably above roughly 500 °C. Chromium carbide grades sacrifice some hardness but keep their properties to much higher temperatures, which makes them the standard choice for boiler tubes and hot gas paths.

These figures are guidelines and shift with coating density, load and atmosphere, so a trial on the real part remains the best confirmation.

Melting Point and Thermal Expansion: Choosing an Oxide Ceramic Powder for the Substrate

The melting point tells you how much heat input is needed, while the thermal expansion coefficient tells you whether the coating will survive thermal cycling. A large mismatch between coating and steel substrate produces residual stress and eventually spallation, particularly on thick layers. This is why zirconia, with its comparatively high expansion, is used for thermal barriers over nickel alloys, while alumina and chromia are preferred where hardness and wear resistance are required.

If the substrate expansion is far from that of the coating, a metallic bond coat such as NiCrAlY or a graded layer is normally worth adding before the top oxide layer.

Troubleshooting Common Ceramic Coating Defects

High Porosity

Excess porosity usually points to unmelted particles or a spray distance that is too long. Check the particle size distribution first, then raise the plasma power or shorten the stand-off distance in small steps of 10–20 mm. If the powder itself is hollow or poorly sintered, no parameter change will fully compensate.

Cracking in Laser Clad Layers

Cracks appear when a hard ceramic-rich layer cools too quickly on a rigid substrate. Preheating the part to 200–400 °C, reducing the ceramic fraction, or lowering the scan speed all decrease the thermal gradient. Depositing thinner layers with a nickel-based transition zone is another proven remedy.

Delamination at the Interface

Poor adhesion is more often a surface preparation problem than a powder problem. Grit blasting to Sa 3 with a roughness of Ra 3–6 µm, spraying within a few hours of blasting, and keeping the substrate free of oil are the basic requirements. Our technical team is glad to review your parameters and recommend a suitable Ceramic Powder or Ceramic Alloy Powder grade if you are chasing a recurring defect.

Incoming Inspection Checklist for Ceramic Powder Batches

Batch-to-batch consistency is what keeps a coating line stable, so a short incoming inspection saves far more time than it costs. The items below can be checked with modest laboratory equipment and give a reliable picture of whether a new lot will behave like the previous one.

• Particle size distribution by laser diffraction, comparing D10, D50 and D90 with the previous lot.
• Hall flow rate on a 50 g sample, and apparent density, since both reveal changes in morphology.
• Morphology under SEM: spherical, agglomerated-and-sintered or fused-and-crushed, as each behaves differently in the gun.
• Chemical composition and phase content, including free carbon or unwanted phases in cermet powders.
• Loss on drying, to confirm moisture is within the limit before the powder goes into the feeder.

We supply a test report with every shipment, and we can keep retained samples of each lot for traceability if your quality system requires it.