Microstructure of TiC-Based Coatings on Cemented Carbide Derived by Sol-Gel Routes
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TiC is extensively used as an intermediate layer or final coatings on cemented carbide tools or wear parts due to its high hardness, thermal stability, wear resistance, oxidation resistance, and low friction coefficient.[1] Vapor deposition methods are widely used in industrial scale to coat TiC on cemented carbide.[2–4] However, expensive furnaces are required and the controlling of processing parameters is complicated. Furthermore, CVD coatings are typically deposited at relatively high temperatures of 773 K~1323 K (500 C~1050 C),[5] which has neglect effect on the toughness and hardness of substrates and adhesion strength of coatings.[6] Sol-gel technique is a simple and inexpensive coating method, which has many advantages including low processing temperature, better control of coating composition, and ease of coating on substrates of complex geometries.[7] Sahnesarayi[8] synthesized the TiO2 polymeric sol through partial hydrolysis and condensation of titanium isopropoxide as the
MEI YANG, KAIFENG QI, KUN HUANG, JIANXIONG DENG, and JIA LIU are with the College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, People’s Republic of China. ZHIXING GUO is with the School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065, People’s Republic of China. Contact e-mail: [email protected] Manuscript submitted June 23, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
starting material. The TiO2 coatings were prepared on the stainless steel substrate via dip-coating at a withdrawal speed of 3 cm/min and heat treating at 673 K~973 K (400 C~700 C) for 30 minutes. Dong[9] synthesized anatase TiO2 thin films on fused quartz by sol-gel dip-coating method followed by annealing at 800 K (527 C). Hu[10] prepared dense Al2O3 precursor using aluminum isopropoxide (Al(OPri)3) as raw material, and dense Al2O3 thin film were obtained by spin-coating of the sol on fused Pt/Ti/SiO2/Si wafers and followed by drying at 473 K (200 C) for 10 minutes, pyrolyzing at 673 K (400 C) for 10 minutes, and calcining at 773 K (500 C) for 3 hours. Chen[11] prepared boehmite sol at 363 K(90 C) from aluminum isopropoxide solution by a sol-gel route. Al2O3 film was fabricated after depositing the sol on cemented carbide and sintering at 1423 K to 1573 K (1150 Cto 1300 C). It should be noted that sol-gel method is typically characterized by hydrolysis and condensation of metal salt, followed by calcination, thus generally yielding an oxide other than carbide. In the paper, sol-gel method is utilized to prepare TiC-based coating. TiO2 sol is prepared and deposited onto cemented carbide compact other than as-sintered bodies, and then TiC-based coating can be achieved due to the carbothermal reaction of TiO2 during vacuum sintering of the TiO2 sol-coated green body. Furthermore, neglect effect of coating process on the substrate can be avoided since the compact other than sintered cemented carbide is used as the substrate. The microstructure and formation mechanism of the
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