No it's not constant. The speed may be constant but the direction of the tangential velocity is changing continuosly as the object moves along acircular path.

Why does tangential velocity change?

A particle moving at higher speed will need a greater radial force to change direction and vice-versa when the radius of the circular path is constant. ... We need a tangential force to affect the change in the magnitude of a tangential velocity. The corresponding acceleration is called tangential acceleration.

What affects tangential velocity?

Tangential speed measures how quickly an object going in a circle is traveling. ... If two objects take the same amount of time to complete a revolution, the object traveling in the circle with the greater radius will have the faster tangential speed. A larger radius means the object travels a greater distance.