The most common misconception when buying "round SiC powder" is that spherical means one and the same thing. In reality, SiC powders that look round divide into at least two categories, with entirely different manufacturing principles, prices, and applications. The bottom line: SiC powder should be graded into three types — crushed angular, spray-dried granule, and plasma-spheroidized — and the crux of supplier verification is not "is it spherical" but "is it a spray-dried granule or a plasma bead."
Three Grades of SiC Powder
| Grade | Process | Morphology | Rough price | Main use |
|---|---|---|---|---|
| ① Crushed (angular) | Milling + sieving | Sharp angular | ~$2–3/kg | Abrasives |
| ② Spray-dried granule | Fines + binder + sintering aids, spray-dried | Porous spherical (dimpled) | $5–15/kg | Press sintering |
| ③ Plasma spheroidized | Plasma melt and resolidify | Dense true beads | Tens of $/kg+ | Thermal spray, 3D printing (AM) |
① Crushed (Angular) Powder
The most basic form. It is made by milling SiC lumps and classifying by sieve. The morphology is sharp and angular, and it is used mainly as an abrasive. One misconception needs correcting here: angular does not mean low quality. Morphology (angular vs spherical) and purity (impurity content) are independent axes. Angular powder can be high purity. The real weakness of angular powder is not purity but flowability — angular particles interlock, flow poorly, and fail to fill a press die uniformly, creating density variation in the green body.
② Spray-Dried Granule (RTP, Ready-to-Press)
This is the grade used for press-sinter forming. A slurry of fine (sub-micron) SiC mixed with binder and sintering aids (carbon, B₄C, and similar) is spray-dried, and as the small droplets dry they form porous spherical granules. These granules look round, but they are not solid beads — they are porous agglomerates of fines held together.
The telltale signature of a spray-dried granule is a surface dimple. During droplet drying the surface collapses inward, leaving a donut-shaped depression. Under SEM this dimple reads like the fingerprint of spray drying. In practice these granules are designed to crush during press forming, and the binder that was mixed in is removed by thermal decomposition during sintering. Detecting a carbon-rich composition or B₄C is a normal signal of a pressureless-sintering sintering-aid formulation.
③ Plasma-Spheroidized Powder
The most expensive grade. Melting SiC particles in a plasma and letting them resolidify produces dense true beads with almost no internal voids, unlike the porous granules. Their excellent flowability and packing density make them a feedstock for thermal spray coating and metal 3D printing (additive manufacturing, AM). The price climbs to tens of dollars per kilogram and up.
Why the Distinction Matters
Even among "round SiC powders," a mismatch in application causes a process to fail. Feeding plasma beads into a press-sinter line gives different forming and sintering behavior; conversely, feeding porous spray-dried granules into a thermal-spray or AM line will not produce acceptable coating or build quality. Notably, some products sold under the name "granule" in the market are in fact closer to crushed angular powder, and they are hard to tell apart from photos or the naked eye alone. That identification problem is examined with a real case in Powder quality verification methodology.
The Crux of Supplier Verification: Does the Vendor Own a Spray Dryer?
If you are sourcing RTP granules for press sintering, whether the vendor actually owns and operates a spray dryer is the key verification point. Without a spray-drying process, no one can make genuine porous spherical granules. To distinguish a distributor reselling angular fines as "granules" from an actual granule manufacturer, verify the following.
- Process audit: whether a spray dryer is owned and running (video or on-site audit)
- SEM morphology: porous spherical + dimples (donut-shaped depressions) = genuine spray-dried granule
- Composition: use EDS to confirm the carbon-rich, B₄C sintering-aid formulation
- Lot certificate (COA): particle size (D50/D90), free Si, moisture, SiC content
Even the price band allows a first-pass screen. Abrasive-grade angular runs $2–3/kg, spray-dried granules $5–15/kg, and plasma beads tens of dollars per kilogram and up; a quote that falls outside that ladder warrants suspicion of a grade mismatch. The full price ladder and market trend are covered in 2026 global SiC market outlook.
Frequently Asked Questions
Is angular SiC powder lower quality than spherical?
No. Morphology and purity are separate axes. Angular powder can be high purity, and for many applications such as abrasives, angular is actually the better fit. The real weakness of angular powder is lower flowability, which can cause uneven die filling in pressing.
How do I tell a spray-dried granule from a plasma-spheroidized powder?
SEM morphology is the clearest indicator. A spray-dried granule is porous and spherical with surface dimples (donut-shaped depressions). A plasma-spheroidized powder is a dense true bead through and through. The price bands also differ sharply ($5–15/kg vs tens of dollars per kilogram and up).
What does a dimple in an SEM image mean?
A dimple (a donut-shaped depression) is the telltale signature of spray drying. It forms as the droplet surface collapses during drying, indicating that the powder is a spray-dried granule.
If carbon or B₄C is detected in an RTP granule, is that an impurity?
No. It is a deliberately added sintering aid for pressureless sintering and is a normal signal. A carbon-rich composition and B₄C detection support that the granule is intended for press-sinter forming.
References (Public Sources)
- General powder metallurgy and ceramic forming literature (spray drying, pressureless sintering)
- Standard procedures for SEM/EDS-based particle morphology and composition analysis
Nami Tech Solution (NTS) is a Korea-based trading company specializing in global sourcing of semiconductor and energy materials. Because SiC powders differ in manufacturing principle and application by grade, NTS selects and supplies the right grade to spec through SEM/EDS, PSA, and XRD lot verification and vendor process audits.
If you need to source SiC powder matched to your application — RTP granules, abrasive grade, or spheroidized powder — contact us at [email protected] or use our contact page.