中国科学院力学研究所机构知识库

  在高温铝蚀以及冷热交变的恶劣服役环境下，压铸模具表面往往因出现铝蚀、 氧化、热疲劳裂纹等损伤，在冷热交变下产生的循环热应力的促进下导致模具断 裂失效。采用物理气相沉积（PVD）技术在其表面沉积 Ti 基涂层是目前比较有 效的防护手段，然而涂层在服役过程中常常因出现剥落或开裂等不稳定因素导致 结合失效，研究表明，涂层在制备过程中产生的高残余应力是导致其发生结合失 效的主要原因。

基于前人们的大量研究表明，在涂层的沉积过程中，高能惰性气体离子（Ar+） 在晶格缺陷或间隙位置的夹持会导致涂层产生过高残余压应力，而金属离子（成 膜离子）因其主要结合在晶格位置，可以减少沉积过程中所产生的生长应力，并 且金属离子辐照同样具有惰性气体离子轰击的所有优点。基于此，本文利用高功 率脉冲磁控溅射（HiPIMS）具有高离化率以及离子可调控等特性，通过增大金属 离子与惰性气体离子通量比例（NTi+ / NAr+），降低TiN涂层的残余应力。考虑到 涂层的生长受到等离子体中离子通量、离子比例以及离子能量的共同作用，通过 调控偏压大小来控制离子轰击能量，进一步提升TiN涂层的力学性能。本文主要 结论如下：

1．通过研究不同电源参数下等离子体发射光谱以及离子流的变化，结果表 明脉冲放电前期由Ar+放电为主导，后期由Ti+放电为主导，离子流在脉冲放电结 束后出现的第二峰位是以Ar+为主的离子峰，通过在峰值电流达到最大值时停止 放电，可使气体稀薄效应达到最强，有效防止Ar原子回充，在Ti+通量基本不变 的前提下使得NTi+ / NAr+从2.3提高到7。

2．通过增大NTi+ / NAr+的比值来降低Ar+轰击带来的危害，随着NTi+ / NAr+ 从 2.3 提高到 7，TiN 涂层的择优取向由（111）逐渐转向（200），沉积速率从 15nm/min 提高到 17nm/min，涂层的残余应力从6.8GPa 降低到0.9GPa，涂层的 韧性（H/E 和 H3/E2）得到有效的提升，涂层的膜基结合力也得到明显的改善， 证实了通过减少Ar+的轰击来降低涂层残余应力可行性。

3．通过控制离子轰击能量来对TiN涂层力学性能进一步提升，随着偏压从 0V 增大到-200V，TiN涂层的择优取向由（200）转变为（111），同时涂层晶粒尺 寸从41nm减小到9nm，使得涂层的硬度也从14.1GPa提高到27.3GPa，表明调 整偏压的大小，通过影响TiN涂层的晶体取向以及晶粒尺寸等微观结构，可以有 效提高涂层的硬度。残余应力从0.7GPa增加到5.7GPa，TiN涂层的H/E和H3/E2 的值与膜基结合力均呈先上升后下降的趋势，表明 TiN 涂层的韧性与膜基结合 力受综合性能的影响。

In the high temperature aluminum corrosion as well as hot and cold alternating severe service environment, die casting die surface often due to aluminum corrosion, oxidation, thermal fatigue cracks and other damage, in the hot and cold alternating cyclic thermal stresses generated by the promotion of the mold fracture failure. The use of physical vapor deposition (PVD) technology in its surface deposition of Ti-based coating is currently more effective means of protection, but the coating in service often due to the emergence of flaking or cracking and other unstable factors lead to the combination of failure, the study shows that the coating in the process of preparation of the high residual stress is the main reason for the occurrence of the combination of the main reasons for failure.

Based on a large number of previous studies, it has been shown that in the deposition process of coatings, the clamping of high-energy noble gas ions (Ar+) in lattice defects or interstitial positions can lead to excessive residual compressive stresses in the coating, while metal ions (film-forming ions), which are mainly bonded to the lattice positions, can reduce the growth stresses generated in the deposition process, and the irradiation of metal ions also has all the advantages of the bombardment of noble gas ions. . Based on this, this paper takes advantage of the fact that high-power pulsed magnetron sputtering (HiPIMS) has the properties of high dissociation rate as well as ion tunability, and reduces the residual stresses in TiN coatings by increasing the ratio of metal ions to noble gas ion flux (NTi+ / NAr+). Considering that the growth of the coating is subject to the joint effect of ion flux, ion ratio and ion energy in the plasma, the ion bombardment energy is controlled by regulating the bias size to further enhance the mechanical properties of the TiN coating. The main conclusions of this paper are as follows:

1. By studying the plasma emission spectra and the changes of ion current under different power supply parameters, the results show that the pulse discharge is dominated by Ar+ discharge in the early stage and Ti+ discharge in the late stage, and the second peak position of the ion current appears at the end of the pulse discharge is the ion peak dominated by Ar+, and the gas thinning effect can be made to reach the strongest and the Ar+ atom backfilling can be prevented efficiently by stopping the discharge at the time when the peak current reaches the maximum value. By stopping the discharge when the peak current reaches the maximum, the gas thinning effect can be maximized, effectively preventing Ar+ from being recharged, and increasing the NTi+ / NAr+ from 2.3 to 7 under the premise that the Ti+ flux is basically unchanged.

2. Reducing the harm caused by Ar+ bombardment by increasing the ratio of NTi+ / NAr+, with the increase of NTi+ / NAr+from 2.3 to 7, the selective orientation of the TiN coatings gradually shifted from (111) to (200), the deposition rate was increased from 15 nm/min to 17 nm/min, and the residual stress of the coatings was reduced from 6.8 to 0.9 GPa, and the coatings' The toughness (H/E and H3/E2) of the coating was effectively improved, and the film-base bonding of the coating was also significantly improved, confirming the feasibility of reducing the residual stress of the coating by reducing the bombardment of Ar+.

3. The mechanical properties of the TiN coatings were further enhanced by controlling the ion bombardment energy. As the bias voltage increased from 0 V to 200 V, the preferential orientation of the TiN coatings was changed from (200) to (111), and at the same time, the grain size of the coatings was reduced from 41 nm to 9 nm, which resulted in the hardness of the coatings being increased from 14.1 to 27.3 GPa, indicating that the adjusting of the size of the bias voltage, by affecting the microstructure of the TiN coating such as crystal orientation and grain size can effectively improve the hardness of the coating. The residual stress increases from 0.7 GPa to 5.7 GPa, and the values of H/E and H3/E2 of TiN coatings and the bonding strength of the film substrate show a tendency of increasing and then decreasing, which indicates that the toughness and the bonding strength of the film substrate of the TiN coatings are affected by the comprehensive performance.