| The application of Ti-coated diamond, protected by the coatings and formed chemicalmetallurgical bonding, has greatly improved the lifetime of diamond tools. However, theresearch to which performance change of coated diamond caused by different platingconditions was seldom paid attention. In this paper, Ti-coated diamond was prepared at atemperature in the range of730oC to910oC and holding time from0.5h to6h throughvacuum slow vapor deposition process. The Ti-coated diamond was also fabricated intocomposites with metal bond by hot-press sintering. The surface morphology, coatingthickness was studied by X-ray diffraction, scanning electron microscope, and energydispersive spectroscopy analysis. The compressive fracture strength, TI of coated diamondand bending strength of composites was researched.The results showed that the surface morphology of Ti-coated diamond was intenselyinfluenced by coating temperature. At low coating temperature (730oC), the coating israther thin, and TiC is generated. The thickness of coating with rise of coating temperature,plating thickness increased as well as content of TiC. At the relatively high temperature, Tiwas found inside the coatings. The plating thickness is continuously increasing until thefinal failure by generation of cracks on coating surface at the temperature like870oC. Theholding time also has similar result. The bending strength of composite segments changesbecause of the performance alteration in Ti-coated diamond. At lower temperature, thebonding strength between diamond and metal matrix is relatively weak, however, as theevaluation of coating temperature, the bonding strength of the composites improved to themaximum566MPa (830oC) then decreased sharply during the process. The transverserupture strength of composites was also affected by holding time of coating, withextension of holding time, the bonding strength between diamond and metal matrix alsoincreased firstly then decreased, and compared with that of coating temperature, therangeability was smaller. With the aid of microscopic calculation formula, the bondingstrength value between coating and metal matrix was calculated as232MPa, it is thusclear that coating layer plays a tremendous role in composites. Considering that thestability of diamond is influenced by temperature improvement, TI of two types of diamond SMD and MBD was measured, the TI value of SMD type decrease significantlyafter850oC, however, the TI value of poor grade type MBD diamond decreased sharplybefore790oC. In order to avoid the degeneration of thermal stability of diamond, theoptimum condition should be based on the premise that diamond is safe. Then, maximumbonding strength of holding time was pursued so as to abtain the optimal coatingcondition.Ti-coated diamond, supported from intermediary role of coating layer, could easilymetallurgical bonded with surrounding metal matrix, which Fe-based metal bond materialwith low price is widespreadly used. If plating condition is improved so as to acquireoptimal coating layer, the property of Fe-based bonded diamond tools will get greatlyimproved. |
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