【作者】 郑亚军；

【导师】 冷永祥；

【作者基本信息】 西南交通大学 ， 机械设计及理论， 2013， 硕士

【摘要】 钛合金具有比强度高、耐高温和耐腐蚀等一系列优异特性,广泛用于航空航天、船舶、机械和生物医学工程等领域。但是,钛合金高温强度高、热导率低、弹性模量小、化学活性高且与其它金属摩擦系数大,导致钛合金切削加工相当困难。而且干切削过程产生大量切削热,切削温度高,刀具磨损严重,导致钛合金加工效率低下,刀具寿命短。根据钛合金切削加工特点,为了提高钛合金切削刀具的寿命,本文以Ti(Cr,Al)SiC(O)N涂层硬质合金刀具为研究对象,旨在探索适合钛合金切削的新型涂层材料,为今后涂层刀具材料的设计和选择提供参考。本文研究了利用等离子增强磁控溅射方法在硬质合金表面制备的Ti(Cr,Al)SiC(O)N涂层(TiSiCN、CrSiCN、CrAlSiCN、CrAlSiCON、TiAlSiCN、 TiAlSiCON)的力学性能及其热稳定性。通过对CrAlSiCON、TiAlSiCN、TiAlSiCON涂层和硬质合金基体在空气中进行600℃高温处理,研究了高温处理对涂层相结构、膜基结合力、硬度的影响,研究结果表明：硬质合金基体在600℃时氧化非常明显,氧化产物主要是由WC和Co氧化生成的WO3和COWO4,硬度急剧降低,而三种涂层在该温度下没有发生氧化,膜-基结合强度和硬度等性能保持不变。对TiSiCN、 CrSiCN、CrAlSiCN、CrAlSiCON、TiAlSiCN、TiAlSiCON涂层和基体在空气气氛中进行700℃高温处理,进一步研究涂层的抗氧化性、高温硬度、摩擦磨损性能,研究结果表明：基体氧化更为严重,表面出现一层约0.2mm厚的氧化层,表面硬度由45GPa降为2GPa。TiSiCN和CrSiCN涂层氧化分别生成TiO2和Cr2O3,对比TiAl基和CrAl基涂层,发现TiAl基涂层中Ti氧化生成Ti02,而CrAl基涂层中Cr元素没有被氧化,这说明CrAl基涂层中的A1元素明显提高了涂层的抗氧化性能。CrAl基涂层在700℃下仍具有较高的硬度。利用CrAlSiCN、CrAlSiCON、TiAlSiCN、TiAlSiCON涂层和Ti6A14V(Ti64)球在400℃下进行摩擦磨损试验,研究结果表明：400℃下涂层与Ti64对磨的摩擦系数高于常温下的摩擦系数,含氧涂层的摩擦系数高于不含氧涂层的摩擦系数,CrAlSiCON涂层在400℃下的耐磨性能最好。通过铣削钛合金评价了TiSiCN、CrSiCN、CrAlSiCN、CrAlSiCON、TiAlSiCN和TiAlSiCON涂层表面改性的硬质合金(K40UF)立铣刀具的切削性能,结果表明：TiSiCN和CrSiCN涂层刀具的铣削性能最好,Cr-基涂层刀具的铣削温度高于Ti-基涂层刀具的,TiAl-基和CrAl-基涂层的铣削温度低于Ti-基和Cr-基涂层刀具,这说明Al元素的加入可以降低涂层刀具的铣削温度。所用刀具加工钛合金时形成典型的锯齿状切屑,不同涂层刀具对切屑形态没有显著影响。更多还原

【Abstract】 Titanium alloys are widely used in aerospace, marine, machinery and biomedical engineering because of their excellent properties, such as high specific strength, high temperature and corrosion resistance. But it is well known that the titanium alloys machining process is difficult due to the material’s high-temperature strength, very low thermal conductivity, relatively low modulus of elasticity, chemical reactivity and high friction coefficient with other metals. And during dry cutting process, more cutting heat results in the higher cutting temperature and inereased tool wear which lead to low machining efficiency and short tool life existed in milling of titanium alloy. According to the characteristics of titanium alloys processing, in order to extend the service life of the tools for machining titanium alloys, the Ti(Cr,A1)SiC(O)N coatings are choosed as the study object in this paper so as to explore new coating materials for titanium alloy cutting and provide reference for the design and selection of tool coating material.In this paper, the mechanical and thermal stability of Ti(Cr,A1)SiC(O)N coatings (including TiSiCN、CrSiCN、CrAlSiCN、CrAlSiCCON、TiAlSiCN and TiAlSiCON) which were deposited on cemented carbide substrate using plasma enhanced magnetron sputtering method were evaluated. The CrAlSiCON, TiAlSiCN, TiAlSiCON coatings and cemented carbide substrate were undergone heat treatment at600℃during2h in air. The changes in structure, adhesion strength and hardness of the coatings and substrate vs. temperature have been analyzed using X-ray diffraction, scratch testing as well as hardness testing. The results indicated that the cemented carbide substrate was oxidized very obviously at600℃and the main oxidation products are WO3and COWO4generated by the WC and Co, and hardness drastically reduced. But all the above three coatings were not oxidation at600℃, and the adherence strength and hardness had not changed much. The TiSiCN, CrSiCN, CrAlSiCN, CrAlSiCON, TiAlSiCN, TiAlSiCON coatings and cemented carbide substrate were undergone heat treatment at700℃in air for2h in order to further investigate the coatings oxidation resistance, high temperature hardness and friction and wear behaviour. The results show:the substrate oxidation was more serious than at600℃and the formation of a homogeneous oxide layer in the substrate surface, approximately0.2mm thick, so the surface hardness was dropped from45GPa to2GPa. The TiSiCN and CrSiCN coating were slightly oxidized at700℃and the main oxidation products are TiO2and Cr2O3generated by the Ti and Cr. Compared with the CrAl-based and TiAl-based coatings, it can be found that TiAl-based coatings were oxidized at700℃and the main oxidation products are TiO2generated by the Ti but the Cr element in the CrAl-based coatings were not oxidation. It indicated that the Al element is significantly improved oxidation resistance of the CrAl-based coatings. The CrAl-based coatings still have a higher hardness at700℃. Friction and wear tests were carried out using pin-on-disc with Ti64balls at400℃; the CrAlSiC、CrAlSiCON、TiAlSiCN and TiAlSiCON coatings were used. The results show: The CrAlSiCN、CrAlSiCON、TiAlSiCN and TiAlSiCON coatings had a higher friction coefficient at400℃than at room temperature. And the oxygen-containing coatings friction coefficients were higher than the oxygen-free coatings. The wear resistance of CrAlSiCON coating was best at400℃.The cutting performance of the TiSiCN, CrSiCN, CrAlSiCN, CrAlSiCON, TiAlSiCN and TiAlSiCON coated K40UF cemented carbide end-mills were evaluated by milling Ti64alloy. The results showed that the TiSiCN and CrSiCN coated tools had a better cutting performance than other coated tools. The Cr based coatings had higher mlling temperature than the Ti based coatings. The TiAl-based and CrAl-based coatings had lower milling temperature than the Ti/Cr-based coatings. It indicated that the addition of A1element to Ti/Cr-based coatings can reduce milling temperature. The chip of cutting Ti64is the typical serrated chip. Different coated milling cutter had no significant effect on the morphology of chip.更多还原