Diamond Block Atmosphere Control
Simplified Atmosphere Generation

Diamond Block - A True Gem in Atmosphere Control 

Sentry Diamond Blocks are easy-to-use, removable inner linings for our Model AY furnaces. They are composed of a carbonaceous material, which is slowly consumed at steel hardening temperatures. This automatically generates a protective, gaseous atmosphere to preventharmful oxidizing effects such as scale and decarburization. Decarburization is the loss of carbon from the surface of steel. This results in a soft surface where a hard surface is desired, but it can be prevented through the use of Diamond Blocks.

No operator monitoring or adjustments are required, and the atmosphere remains constantly correct. Diamond Blocks produce quality hardening for all types of tool steel, and tools hardened by this method will yield maximum useful service.  


When you control the atmosphere, you control the quality.

The secret to DIamond Block's effectiveness is actually no secret at all -- it's just sound science. When air is presented in a hardening furnace, the oxygen combines with the steel and produces a scaled surface. The  atmosphere can be enriched with various forms of carbon to limit undesirable scaling, but this can also result in tools being badly decarburized. Further enrichment of the atmosphere decreases the amount of decarburization until it finally disappears. A neutral point is reached where the steel is neither giving up nor absorbing carbon. This neutral point, which is ideal for hardening tool steels, is automatically achieved by Diamond Block.

Tools hardened by the Diamond Block method retain their initial sharp, clean-cut edges with no scale, decarburization or reduction in size. Maximum surface hardness is obtained and finishing operations are reduced or eliminated. Without oxidation, tools will not overheat in the furnace and it is safe to allow for ample hardening time to achieve maximum hardness and proper grain structure. 

Click here for detailed information on the use of Sentry Diamond Blocks.

America’s oldest steel heat treating furnace maker.