April 04, 2022

Aluminum Oxide Vs Silicon Carbide Cutting Grains

When it comes to finishing and grinding, fabricators have a wealth of product options at their disposal – though they run the gamut in terms of cost-to-performance ratios. Abrasive grains don’t usually constitute an enormous overhead, but labour costs of grinding can become exorbitant if the right tools – and indeed the right grains – aren’t deployed. Production operations and small-scale workshops likely expend 10—15% of their labour on metal fabrication and finishing processes.  

By utilising cutting grains which have a better bonding affinity, higher stock removal rates, and increased product longevity, fabricators can dramatically increase productivity. In this article, we will compare the performance of aluminum oxide abrasives to silicon carbide cutting grains, to demonstrate the added value of precision finishing products.  

Different Types of Abrasive Cutting Grains 

Aluminum oxide (Al2O3) is one of the oldest abrasives still used in industrial finishing applications. Until the 1970s, it was practically the only choice for metal grinding applications, and it remains popular today, owing to its cost-attractiveness and relatively good performance. However, the tough cutting edges of commodity alumina dull quickly, translating to poor product service life. Innovations in particle engineering have yielded several spectacular enhancements to the alumina formula; notably fused crystalline alumina-zirconia and ceramic alumina.  

Is Silicon Carbide a Good Abrasive? 

Silicon carbide (SiC) is a less common candidate material for abrasive applications, but with a hardness of 25 GPa but with a Mohs Scale hardness of 9, second only to diamond, it can make for exceptional cutting grains. Particles of SiC are also friable, which means they tend to fracture during use, exposing new sharp edges. This permits longer service and faster material removal rates.  

Synthetic SiC is generally produced by heating fine silica (SiO2) particles in a graphite electric resistance furnace at temperatures approaching 2500°C. This makes it relatively easy to manufacture. So, the cost-to-performance properties of silicon carbide cutting grains are attractive. But does this make silicon carbide cutting grains superior to alumina? 

Which is Better Silicon Carbide or Alumina Abrasives? 

Brown fused alumina is a commodity abrasive which cannot compete with the tailored performance of modern engineered particles like alumina zirconia. However, the fundamental structure of alumina provides exceptional durability and enhanced cutting action – hence the continued development of improved systems based on the same basic chemical formulation. Brown fused alumina offers superior toughness to silicon carbide, and also it eliminates the potential for negative reactions between the abrasive and work material, such as what occurs when grinding steel with silicon carbide. 

Monocrystalline alumina abrasives are derived from electronic fusion of high-purity aluminum oxide with specialty dopants. This yields  finely engineered product in which every single grain is an individual crystal with sharp, strong edges. The amount of hard-wearing cutting facets is subsequently maximised, as is the grain’s toughness as well as its bonding affinity. This results in a long-lasting cutting grain suitable for high-throughput resin bond and vitrified applications, serving well in critical markets like aerospace and automotive finishing.  

The bottom line is that silicon carbide cutting grains work well for various grinding applications, with their high hardness and tailored friability. But ceramic alumina is the next great innovation in abrasives, and it sets a new benchmark of performance for finishing and grinding.  

Looking for Monocrystalline Alumina Grains? 

Saint-Gobain Abrasive Grains’ proprietary monocrystalline alumina abrasive is MA88, a high-purity solution with exceptional stock removal rates. It adds value to finishing and grinding processes in a multitude of ways, accelerating key finishing tasks while preserving cutting tool performance. Refer to our MA88 alumina abrasives product page for a comparison between our solution and other monocrystalline alumina grains. Or contact a member of the team if you have any questions.