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2025
Conference Paper
Title
Laser surface polishing of CVD microcrystalline diamond coatings
Abstract
Microcrystalline diamond coatings (MCD) enable the attainment of very high mechanical properties and tribological wear resistance in coated tools, such as sheet metal stamping dies.
However, MCD coatings are characterized by significantly higher roughness than DLC coatings, due to the characteristics of the CVD process in which they are applied. This results in a need for further post-processing, which is challenging because of the diamond's high hardness.
Therefore, in this study, the surfaces of MCD coatings applied to two types of WC-Co substrates, one etched and the other with smooth interlayers, underwent treatment by ultrashort pulse laser surface polishing (LSP).
The effectiveness of LSP was verified by assessing the roughness and tribological properties of the machined surfaces and comparing them with the results obtained for mechanically machined surfaces and reference DLC coatings. The values of Spk and Sa parameters were 0.376µm/0.157µm and 0.214µm/0.112µm, respectively for as-coated/laser polished surfaces. Tribological tests conducted on MCD-treated surfaces using a strip drawing test against EN AW 5182 aluminum alloy sheets presents values of friction coefficients of 0.17-0.21 with lubrication and 0.28-0.35 for dry friction conditions. The values measured for the mechanically polished coatings were 0.18-0.20 and 0.40-0.42, for lubricated and dry tests conditions respectively.
The results obtained indicate that LSP can be used to reduce the roughness of MCD diamond coatings and enhance the technological properties of MCD coated press-forming tools, which can be employed in the deep drawing of aluminum sheets with minimized lubrication.
However, MCD coatings are characterized by significantly higher roughness than DLC coatings, due to the characteristics of the CVD process in which they are applied. This results in a need for further post-processing, which is challenging because of the diamond's high hardness.
Therefore, in this study, the surfaces of MCD coatings applied to two types of WC-Co substrates, one etched and the other with smooth interlayers, underwent treatment by ultrashort pulse laser surface polishing (LSP).
The effectiveness of LSP was verified by assessing the roughness and tribological properties of the machined surfaces and comparing them with the results obtained for mechanically machined surfaces and reference DLC coatings. The values of Spk and Sa parameters were 0.376µm/0.157µm and 0.214µm/0.112µm, respectively for as-coated/laser polished surfaces. Tribological tests conducted on MCD-treated surfaces using a strip drawing test against EN AW 5182 aluminum alloy sheets presents values of friction coefficients of 0.17-0.21 with lubrication and 0.28-0.35 for dry friction conditions. The values measured for the mechanically polished coatings were 0.18-0.20 and 0.40-0.42, for lubricated and dry tests conditions respectively.
The results obtained indicate that LSP can be used to reduce the roughness of MCD diamond coatings and enhance the technological properties of MCD coated press-forming tools, which can be employed in the deep drawing of aluminum sheets with minimized lubrication.
Author(s)