Ta-C coating is a hydrogen-free carbon element coating, also known as tetrahedral amorphous diamond coating. It has a high ratio of sp to sp3 bonds, with sp3 diamond content reaching between 65-85%, and Vickers hardness up to 5000-7000 HV. Ta-C has some transparency, and when the coating thickness is less than 1 micron, the workpiece will exhibit a rainbow color due to light interference. As the coating thickness increases, the color turns into gray-black. Its excellent adhesion resistance and high hardness make Ta-C coating play a crucial role in the mold and cutting tool industries.