Does brake drum of gray cast iron of hardness 150-180 BHN wear out . what will be the probable causes.?

Yes, a brake drum made of gray cast iron with a hardness of 150-180 BHN can wear out over time. Probable causes of wear include friction from brake pads, thermal cycling leading to thermal fatigue, and environmental factors such as moisture and road debris. Additionally, improper alignment or excessive heat generated during braking can accelerate wear, leading to reduced performance and the need for replacement.