{"id":735,"date":"2026-11-08T23:03:29","date_gmt":"2026-11-08T15:03:29","guid":{"rendered":"https:\/\/siliconcarbide.net\/?p=735"},"modified":"2026-11-08T23:03:29","modified_gmt":"2026-11-08T15:03:29","slug":"recrystallized-silicon-carbide-for-kiln-furniture","status":"publish","type":"post","link":"https:\/\/siliconcarbide.net\/et\/recrystallized-silicon-carbide-for-kiln-furniture\/","title":{"rendered":"\u00dcmberkristalliseeritud r\u00e4nikarbiid ahjutarvikute jaoks"},"content":{"rendered":"

Recrystallized Silicon Carbide (RSiC \/ RSC) \u2014 for Kiln Furniture, Burner Nozzles & High-Temperature Structural Parts<\/span><\/h1>\n

If your furnace cycle runs above 1450\u00b0C, involves rapid heating\/cooling, and a sintering aid or free-silicon phase would become the weak link \u2014 this is the material page you should read before you specify.<\/span><\/strong> RSiC is not \u201canother SiC grade.\u201d It is the grade you choose when <\/span>thermal shock resistance and chemical purity matter more than maximum density<\/span><\/strong>.<\/span><\/p>\n

The one distinction that changes every downstream decision<\/span><\/h2>\n

Most supplier pages list RSiC density, porosity, and strength, and stop there. That information is necessary but not sufficient. The decision-relevant question is: <\/span>why would anyone deliberately choose a silicon carbide with 10\u201320% open porosity over a dense SSiC that looks better on a data sheet?<\/span><\/strong><\/p>\n

The answer is in the microstructure. RSiC is produced by sintering high-purity SiC powder at roughly 2200\u20132450\u00b0C <\/span>without sintering additives<\/span><\/strong>. Silicon carbide grains grow through an evaporation\u2013condensation mechanism, forming direct neck bonds between grains. The material shrinks very little during firing, and the space that dense SiC would fill with sintering aids or free silicon remains as <\/span>connected, open porosity<\/span><\/strong>. That porosity is not a manufacturing defect. It is the functional feature that gives RSiC its thermal shock tolerance and chemical inertness.<\/span><\/p>\n

This is the judgment criterion that separates a buyer who understands SiC grades from one who is comparing only the density column.<\/span><\/p>\n

RSiC vs. SSiC vs. SiSiC\/RBSiC: the selection table most suppliers do not put on their product page<\/span><\/h2>\n
\n
\n
\n
 <\/div>\n<\/div>\n
 <\/div>\n<\/div>\n\n\n\n\n\n\n\n\n\n\n
Item<\/span><\/th>\nRSiC (Recrystallized)<\/span><\/strong><\/th>\nSSiC (Pressureless Sintered)<\/span><\/strong><\/th>\nSiSiC \/ RBSiC (Reaction-Bonded)<\/span><\/strong><\/th>\n<\/tr>\n<\/thead>\n
SiC purity<\/span><\/strong><\/td>\n\u226599%, <\/span>no sintering aid<\/span><\/strong><\/td>\nTypically >98%, contains boron\/carbon sintering aids<\/span><\/td>\nSiC skeleton + <\/span>8\u201315% free silicon<\/span><\/strong><\/td>\n<\/tr>\n
Open porosity<\/span><\/strong><\/td>\n10\u201320% (functional, connected)<\/span><\/strong><\/td>\nTypically <2\u20133%<\/span><\/td>\nNear zero (pores filled with Si)<\/span><\/td>\n<\/tr>\n
Maximum service temperature (air)<\/span><\/strong><\/td>\n~1600\u20131650\u00b0C<\/span><\/strong><\/td>\n~1500\u20131550\u00b0C (aid-dependent)<\/span><\/td>\nLimited to ~1400\u00b0C long-term<\/span><\/strong> (free Si softens)<\/span><\/td>\n<\/tr>\n
Thermal shock resistance<\/span><\/strong><\/td>\nExcellent<\/span><\/strong> \u2014 the primary reason RSiC is selected<\/span><\/td>\nGood, but limited by denser body and aids<\/span><\/td>\nModerate; free silicon introduces a low-melting phase<\/span><\/td>\n<\/tr>\n
Chemical resistance<\/span><\/strong><\/td>\nExcellent \u2014 no free Si, no glassy grain-boundary phase<\/span><\/td>\nGood, but sintering aids can be leached in aggressive chemistry<\/span><\/td>\nFree silicon restricts resistance to strong alkali and HF<\/span><\/strong><\/td>\n<\/tr>\n
Typical geometry \/ cost logic<\/span><\/strong><\/td>\nPlates, beams, tubes, nozzles \u2014 <\/span>thin-walled and thermal-cycled parts<\/span><\/strong><\/td>\nDense wear parts, seals, small precision components<\/span><\/td>\nLarge, complex, near-net-shape parts<\/span><\/strong> where cost matters more than maximum temperature<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Selection rule:<\/span><\/strong> match the grade to <\/span>temperature, atmosphere, chemical contact, and thermal cycle \u2014 not to the abbreviation \u201cSiC.\u201d<\/span><\/strong> If the application requires a dense, low-porosity surface for sealing or wear, RSiC is the wrong choice. If the application involves repeated rapid heating and cooling above 1450\u00b0C, and a free-silicon or sintering-aid phase would become the failure origin, RSiC is often the only SiC grade that survives<\/span>.<\/span><\/p>\n

Technical specifications \u2014 the numbers that matter for specification and incoming inspection<\/span><\/h2>\n

The table below reflects the property range you should use as a <\/span>benchmark when evaluating any RSiC supplier\u2019s data sheet<\/span><\/strong>. Values vary by grain size, forming route, and firing profile; a supplier quoting a single number without a range should be asked for the test standard and sample geometry.<\/span><\/p>\n

\n
\n
 <\/div>\n
 <\/div>\n<\/div>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Parameter<\/span><\/th>\nTypical RSiC range<\/span><\/th>\nEngineering note<\/span><\/th>\n<\/tr>\n<\/thead>\n
SiC content<\/span><\/strong><\/td>\n\u226599 wt%<\/span><\/td>\nNo sintering aid<\/span><\/strong> is the distinguishing purity claim; ask for ICP or XRF verification.<\/span><\/td>\n<\/tr>\n
Bulk density<\/span><\/strong><\/td>\n2.0\u20132.75 g\/cm\u00b3<\/span><\/td>\nLower end indicates higher porosity; density alone is not a quality ranking.<\/span><\/td>\n<\/tr>\n
Open porosity<\/span><\/strong><\/td>\n10\u201320% (functional grades)<\/span><\/strong><\/td>\nSee <\/span>connected<\/span><\/strong> nature of the porosity matters for permeability and thermal shock, not just the percentage.<\/span><\/td>\n<\/tr>\n
Bending strength (RT)<\/span><\/strong><\/td>\n~80\u2013110 MPa<\/span><\/td>\nRSiC is <\/span>not<\/span><\/strong> the highest-strength SiC; do not specify it for load-bearing structural parts where SSiC would be stronger.<\/span><\/td>\n<\/tr>\n
Bending strength (1200\u00b0C)<\/span><\/strong><\/td>\n~90\u2013110 MPa<\/span><\/td>\nStrength retention at temperature is a key advantage over free-silicon-containing grades.<\/span><\/td>\n<\/tr>\n
Max service temperature (air)<\/span><\/strong><\/td>\n~1600\u20131650\u00b0C<\/span><\/strong><\/td>\nAbove this, oxidation kinetics accelerate; inert-atmosphere rating can reach ~1800\u00b0C.<\/span><\/td>\n<\/tr>\n
Max service temperature (inert)<\/span><\/strong><\/td>\n~1800\u00b0C<\/span><\/td>\nSpecify atmosphere explicitly when comparing supplier claims.<\/span><\/td>\n<\/tr>\n
Thermal conductivity (RT)<\/span><\/strong><\/td>\n~23 W\/m\u00b7K<\/span><\/td>\nModerate, not the highest among SiC grades, but adequate for kiln furniture and radiant tubes.<\/span><\/td>\n<\/tr>\n
CTE (20\u20131000\u00b0C)<\/span><\/strong><\/td>\n~4.6\u20134.8 \u00d7 10\u207b\u2076 \/K<\/span><\/td>\nLow expansion is the material-level basis for thermal shock resistance.<\/span><\/td>\n<\/tr>\n
Thermal shock parameter R1<\/span><\/strong><\/td>\n~56 K<\/span><\/td>\nA comparative metric; use it to rank RSiC grades from different suppliers, not as an absolute pass\/fail.<\/span><\/td>\n<\/tr>\n
Grain size<\/span><\/strong><\/td>\n1\u2013150 \u03bcm (longitudinal)<\/span><\/td>\nCoarse grains are normal in RSiC and contribute to the bridged structure; very fine grain may indicate a different grade.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Data sources integrated from supplier data sheets; ranges reflect normal commercial variation, not a guarantee for every geometry<\/span><\/strong>.<\/span><\/p>\n

Where RSiC is the correct specification \u2014 and where it is the wrong one<\/span><\/h2>\n

Specify RSiC when the failure mode is thermal shock or chemical attack at temperature<\/span><\/h3>\n

Kiln furniture for fast-firing cycles.<\/span><\/strong> Thin setter plates, beams, and rollers that see repeated rapid heating and cooling above 1450\u00b0C. The low shrinkage during RSiC sintering allows <\/span>thin-walled sections without warping<\/span><\/strong>, and the open porosity accommodates thermal strain that would crack a denser body<\/span>.<\/span><\/p>\n

Burner nozzles and radiant tubes.<\/span><\/strong> RSiC burner nozzles are specified in shuttle, tunnel, and roller kilns because they resist oxidation and thermal cycling up to ~1650\u20131700\u00b0C without the cracking that occurs in reaction-bonded SiC when free silicon becomes the weak phase<\/span>.<\/span><\/p>\n

Semiconductor and photovoltaic furnace components.<\/span><\/strong> High-purity RSiC is used for <\/span>LPCVD paddles, boats, and diffusion furnace internals<\/span><\/strong> where metallic contamination and particle generation must be controlled. The absence of sintering aids is the specification driver here, not density<\/span>.<\/span><\/p>\n

Component protection tubes in atmosphere furnaces.<\/span><\/strong> The connected porosity of RSiC does not compromise chemical inertness in most furnace atmospheres, and the material tolerates the thermal gradients across the tube wall without spalling.<\/span><\/p>\n

Do not specify RSiC when the requirement is density, sealing, or maximum strength<\/span><\/h3>\n

If the part must hold a vacuum seal, provide a lapped wear surface, or carry a structural load where <\/span>SSiC\u2019s higher density and strength<\/span><\/strong> are the governing properties, RSiC is the wrong grade. Similarly, if the part is large, geometrically complex, and cost-sensitive below ~1400\u00b0C, <\/span>SiSiC\/RBSiC<\/span><\/strong> is usually the more appropriate choice \u2014 its free silicon fills the porosity and enables near-net-shape manufacturing, at the cost of high-temperature and chemical limits<\/span>.<\/span><\/p>\n

Answers to the questions buyers actually ask before sending an RFQ<\/span><\/h2>\n

Is RSiC the same as SSiC?<\/span><\/strong> No. SSiC is pressureless-sintered with sintering aids and is dense. RSiC is recrystallized without additives and retains <\/span>open porosity by design<\/span><\/strong>. They are different materials with different property trade-offs, not synonyms<\/span>.<\/span><\/p>\n

Can RSiC be used above 1650\u00b0C in air?<\/span><\/strong> The practical continuous limit in air is approximately <\/span>1600\u20131650\u00b0C<\/span><\/strong>. Some suppliers cite higher numbers for short-term or inert-atmosphere service; ask for the <\/span>atmosphere and duration<\/span><\/strong> behind any higher claim.<\/span><\/p>\n

Does the porosity mean the part is weaker or lower quality?<\/span><\/strong> It means the material is <\/span>trade-off-optimized for thermal shock and purity, not for maximum strength<\/span><\/strong>. If your application does not require those properties, a denser grade may serve you better. Porosity is a specification variable, not a defect label.<\/span><\/p>\n

What is the difference between RSiC and SiSiC\/RBSiC in chemical service?<\/span><\/strong> SiSiC\/RBSiC contains <\/span>free silicon<\/span><\/strong>, which restricts long-term use above ~1400\u00b0C and reduces resistance to strong alkali and hydrofluoric-acid-containing environments. RSiC has no free silicon and no glassy grain-boundary phase, which is why it is preferred when <\/span>chemical inertness at temperature<\/span><\/strong> is a requirement<\/span>.<\/span><\/p>\n

Can RSiC parts be supplied as custom geometries, not only standard plates and tubes?<\/span><\/strong> Yes, within the geometric constraints of the recrystallization process. RSiC is well suited to <\/span>thin-walled, large-footprint shapes<\/span><\/strong> such as setter plates and beams, but extremely thick sections or complex internal cavities may be more economically produced in a reaction-bonded grade. Share a drawing and the operating conditions for a manufacturability assessment.<\/span><\/p>","protected":false},"excerpt":{"rendered":"

Recrystallized Silicon Carbide (RSiC \/ RSC) \u2014 for Kiln Furniture, Burner Nozzles & High-Temperature Structural Parts If your furnace cycle runs above 1450\u00b0C, involves rapid heating\/cooling, and a sintering aid or free-silicon phase would become the weak link \u2014 this is the material page you should read before you specify. RSiC is not \u201canother SiC… <\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"neve_meta_sidebar":"","neve_meta_container":"","neve_meta_enable_content_width":"off","neve_meta_content_width":70,"neve_meta_title_alignment":"","neve_meta_author_avatar":"","neve_post_elements_order":"","neve_meta_disable_header":"","neve_meta_disable_footer":"","neve_meta_disable_title":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[23],"tags":[],"class_list":["post-735","post","type-post","status-publish","format-standard","hentry","category-recrystallized-silicon-carbide"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/posts\/735","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/comments?post=735"}],"version-history":[{"count":1,"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/posts\/735\/revisions"}],"predecessor-version":[{"id":736,"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/posts\/735\/revisions\/736"}],"wp:attachment":[{"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/media?parent=735"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/categories?post=735"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/siliconcarbide.net\/et\/wp-json\/wp\/v2\/tags?post=735"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}