Carbon brakes were originally used in high performance military aircraft applications. The lower weight & higher energy absorption capability of carbon brakes justified their cost, which historically was higher than the cost of steel brakes.
However, improvements in carbon brake manufacturing & overhaul procedures could reduce the 'per-landing cost' of carbon brakes to the point that they are cost competitive with steel brakes making their increased application of on commercial aircrafts.
✈ Advantages of Carbon Brakes over Steel Brakes :
Longer life: Carbon brakes offer up to twice as many landings per overhaul as steel brakes.
Cost effectiveness: For most operations, the life-cycle costs of carbon brakes are now similar to those of steel brakes.
High performance: Carbon brakes have greater energy absorption capability than steel brakes.
Lightweight: Carbon brakes are significantly lighter than steel brakes. A B737 NG aircraft can save upto 550Lbs with carbon brakes.
Environment: The lower weight of carbon brakes results in slightly lower fuel consumption, which reduces carbon dioxide (CO2) emissions.
Examples : Weight saving achieved due to carbon brakes on following models :