Macor

Macor is the trademark for a machinable glass-ceramic developed and sold by Corning Inc. It is a white material that looks somewhat like porcelain. Macor is a good thermal insulator and is stable up to temperatures of 1000 °C, with very little thermal expansion or outgassing. It can be machined using standard metalworking tools.[1]

Composition

Macor is made up of fluorphlogopite mica in a borosilicate glass matrix. Its composition is roughly: 46 wt% silica (SiO2), 17 wt% magnesium oxide (MgO), 16 wt% aluminium oxide (Al2O3), 10 wt% potassium oxide (K2O), 7 wt% boron trioxide (B2O3), 4 wt% fluorine (F).[2]

Properties

Macor has a density of 2.52 g/cm3,[3] a Young's modulus of 66.9 GPa at 25 °C,[3] a specific stiffness of 26.55 m2s−2, a Poisson’s Ratio of 0.29[3] and a thermal conductivity of 1.46 W/(m·K).[3] It has a low-temperature (25 to 300 °C) thermal expansion of 9.3 K−1.[3] Its compressive strength is 50 lb/in2 (~350 MPa).[3] Nominal engineering properties are comparable to borosilicate glass.[4]

Applications

Macor is used in the following applications:

• Constant and ultra-high vacuum environments
• Laser technology
• Semiconductor / electronic
• Aerospace / space
• Medical/ laboratory equipment
• Fixtures
• Chemical
• Automobile
• Military
• Nuclear

Safety

There are no major safety concerns or toxic effects associated with Macor. The dust created when machining it can be an irritant, and inhalation should be avoided.[6]

Machining guidelines

Key factors for successful machining are proper machining speeds and coolant. Macor can be machined with high-speed steel tools, but carbide tools are recommended for longer wear. Best results achieved by using a water-soluble coolant (such as Cimstar 40 – Pink) especially formulated for cutting and grinding glass or ceramics. No post-firing is required after machining.