Effect of pretreatment strategy on the microstructure, mechanical properties and cutting performance of diamond coated hardmetal tools using HFCVD method

作者：Fan, Shuyu; Kuang, Tongchun^*; Xu, Wei; Zhang, Yuming; Su, Yifan; Lin, Songsheng; Wang, Di; Yang, Hongzhi; Zhou, Kesong; Dai, Mingjiang; Wang, Lei^*

来源：INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS, 2021, 101: 105687.

DOI：10.1016/j.ijrmhm.2021.105687

• Diamond coatings
• WC interlayer
• Pretreatments
• WC-co
• Adhesive strength
• Cutting tests

Diamond coatings are deposited on cemented carbide (WC-Co) tools to lengthen their cutting lifetime. However, their industrial application is held back by poor diamond coating-substrate adhesive strength. In this paper, the cutting performance of differently pretreated diamond-coated WC-Co tools for graphite milling was examined. The WC and Co phases on the surface of the WC-Co substrates were treated by a three-step acid-Murakami-acid chemical etching process (AMA-treatment) followed by physical vapor deposition (PVD) of a WC interlayer with a thickness of 250, 500, or 750 nm. Finally, a multilayered coating was obtained by depositing a 4 mu m thick diamond coating using hot filament chemical vapor deposition (HFCVD). The effect of this composite pretreatment on the adhesive strength and cutting performance of diamond-coated WC-Co tools were studied and compared with diamond-coated WC-Co tools only pretreated by either AMA-treatment or deposition of a 500 nm WC interlayer. Adhesive strength tests assessed by the Rockwell indentation method showed that a combination of AMA-treatment and a thinner WC interlayer (250 or 500 nm) enhanced the adhesive strength (HF1) and cutting performance of these diamond-coated WC-Co tools. SEM and EDS analyses indicated that coating delamination, fracture, diffusion, and adhesive wear were the main failure mechanisms of the cutting tools. Finally, in graphite cutting tests, the diamond-coated WC-Co tool with a composite pretreatment consisting of AMA-treatment and deposition of a 250 nm WC interlayer exhibited significantly enhanced cutting performance (VBmax = 0.18 mm at a cutting length of 200 m) compared with the other pretreated tools.