复合氮化物硬质涂层的HIPIB辐照研究

【作者】 陈军；

【导师】 王富岗；

【作者基本信息】 大连理工大学 ， 材料学， 2009， 博士

【摘要】 磨损是机械零件失效的三种主要原因之一,各种机械零件的磨损所造成的能源和材料的消耗是十分惊人的,世界工业化发达国家的能源约40%是以不同形式消耗在磨损上的,因此,人们一直致力于研究提高材料的抗摩擦磨损性能,表面涂层技术就是极为有效的方法之一。本研究就是在制备硬质涂层的基础上利用强流脉冲离子束（HIPIB）对膜层进行辐照处理,研究辐照前后性能变化规律及其原因。硬质涂层的制备是在Bulat-6型电弧离子镀设备上进行的。根据元素的物理和化学特性,选择Nb、Zr和Cr元素作为组元,采用分离靶技术,通过独立调节靶弧电流,在高速钢基体上制备了(Ti_0.35,Nb_0.65)N、(Ti_0.45,Nb_0.55)N、(Ti_0.47,Zr_0.53)N、(Wi_0.70,Zr_0.30)N、(Ti_0.62,Cr_0.38)N和(Ti_0.67,Cr_0.33)N的均质涂层及(Ti_x,Nb_1-x)N、(Ti_x,Zr_1-x)N梯度涂层。辐照实验是在大连理工大学三束材料表面改性国家重点实验室的TEMP-6型装置上进行的。该装置采用聚合物阳极单极脉冲模式外磁绝缘离子二极管,离子束成分为30%Cⁿ⁺和70%H⁺,加速电压为300-350kV,脉冲宽度为70ns,采用束流密度为60A/cm²和100 A/cm²对（Ti,Nb）N、（Ti,Zr）N均质涂层及（Ti_x,Nb（1-x））N、(Ti_x,Zr_l-x)N梯度涂层进行了辐照处理。SEM观察表明,采用束流密度为60A/cm²的HIPIB辐照后,（Ti,Zr）N均质膜层和(Ti_x,Zr^1-x)N梯度膜层的表面开裂,而（Ti,Nb）N均质膜层表面熔化,并产生了熔滴和熔坑。熔滴的产生是由于烧蚀物质回流沉降于膜层表面而形成,而熔坑的产生是HIPIB辐照时,离子束的轰击使膜层表面颗粒飞溅产生凹坑,而极快的冷却速度使熔融物质无法完全充满凹坑而形成的。而在束流密度为100 A/cm²时,均质膜层和梯度膜层表面全部开裂。利用MM-200摩擦磨损试验机测试了HIPIB辐照前后膜层的抗摩擦磨损性能。结果表明,HIPIB辐照前,（Ti,Nb）N均质膜层的抗摩擦磨损性能明显高于（Ti,Zr）N均质膜层。300N载荷下,(Ti_0.35,Nb_0.65)N和(Ti_0.45,Nb_0.55)N的磨损体积分别为2.389和2.163(×10^-3mm³),而(Ti_0.47,Zr_0.53)N和(Ti_0.70,Zr_0.30)N膜层的磨损体积分别为4.215和5.452(×10^-3mm³)。600N载荷下,(Ti_0.35,Nb_0.65)N和(Ti_0.45,Nb_0.55)的磨损体积分别为2.762和3.217(×10^-3mm³),(Ti_0.47,Zr_0.53)N和(Ti_0.70,Zr_0.30)N膜层的磨损体积分别为6.855和8.468(×10^-3mm³)。(Ti_xNb_1-x)N梯度膜层的抗摩擦磨损性能要优于（Ti,Nb）N均质膜,300N载荷下的磨损体积仅为1.514(×10^-3mm³),600N载荷下的磨损体积为2.139(×10^-3mm³)。而(Ti_x,Zr_1-x)N梯度涂层的抗摩擦磨损性能与均质膜相比无明显改善。HIPIB辐照后,（Ti,Nb）N均质膜的抗摩擦磨损性能明显提高,300N载荷下, (Ti_0.35,Nb_0.65)N和(Ti_0.45,Nb_0.55)N的磨损体积分别为1.771和1.348(×10^-3mm³),600N载荷下,(Ti^0.35,Nb_0.65)N和(Ti_0.45,Nb_0.55)N的磨损体积分别为2.299和2.011(×10^-3mm³)。而(Ti_x,Nb_1-x)N梯度膜的抗摩擦磨损性能反而下降,300N载荷下的磨损体积为2.179(×10^-3mm³),600N载荷下的磨损体积为2.527(×1 0^-3mm³)。为了说明HIPIB辐照对涂层抗摩擦磨损性能的影响原因,测试了辐照前后膜层的相结构、硬度及膜基结合力。X射线衍射分析表明,HIPIB辐照前,（Ti,Nb）N均质膜层具有单一的（Ti,Nb）N相,优先沿（111）方向生长,保留了TiN的立方结构;（Ti,Zr）N均质膜层中出现了（Ti,Zr）N、（Zr,Ti）N、TiN和ZrN四种相,均保留了TiN的立方结构;而在（Ti,Cr）N均质膜层中以（Ti,Cr）N相为主,同时有少量的Cr₂N相产生。(Ti_x,Nb_1-x)N梯度涂层中除（Ti,Nb）N相外,还出现了（Ti,Nb）2N相,而(Ti_x,Zr_1-x)N梯度涂层中仍然是（Ti,Zr）N、（Zr,Ti）N、TiN和ZrN混合相。HIPIB辐照后,无论是（Ti,Nb）N、（Ti,Zr）N均质膜还是(Ti_x,Nb_1-x)N、(Ti_x,Zr_1-x)N梯度膜,其相结构与辐照前相同。利用DMH-2LS超微载荷显微硬度计测量了HIPIB辐照前三种均质涂层及两种梯度膜的硬度及辐照后（Ti,Nb）N均质膜层及两种梯度膜的硬度。测试结果表明,辐照前均质膜层中,（Ti,Zr）N膜的硬度最高,(Ti_0.47,Zr_0.53)N膜层的努氏硬度可达HK3678,(Ti_0.70,Zr_0.30)N膜层的努氏硬度也达到HK3509,而(Ti_0.35,Nb_0.65)N均质膜的努氏硬度仅为HK2651。这主要是由于（Ti,Zr）N均质膜层中存在（Ti,Zr）N、（Zr,Ti）N、TiN和ZrN分离相所致。而(Ti_x,Nb_1-x)N梯度涂层的硬度最高,其努氏硬度达HK3807,但(Ti_x,Zr_1-x)N梯度涂层的硬度为HK3470,与均质膜相比无明显改善。HIPIB辐照后,（Ti,Nb）N均质膜层的硬度有明显提高,(Ti_0.35,Nb_0.65)N膜层的努氏硬度由HK2651提高到HK3054,(Ti_0.45,Nb_0.55)N膜层的努氏硬度由HK3200提高到HK3422,这是由于HIPIB的轰击在膜层内产生位错增殖所致。但(Ti_x,Nb_1-x)N梯度涂层的硬度却显著降低,其努氏硬度由HK3807减少到HK3338。利用CSR-01型划痕实验机测试了辐照前（Ti,Nb）N、（Ti,Zr）N均质膜及(Ti_x,Nb_1-x)N、(Ti_x,Zr_1-x)N梯度涂层及辐照后（Ti,Nb）N均质膜及(Ti_x,Nb_1-x)N梯度膜的膜基结合力。结果表明,辐照前,虽然（Ti,Nb）N均质膜的硬度较低,但其膜基结合力要好于（Ti,Zr）N均质膜。(Ti_0.35,Nb_0.65)N和(Ti_0.45,Nb_0.55)N膜层的膜基结合力分别为65N和59N,而(Ti_0.47,Zr_0.53)N和(Ti_0.70,Zr_0.30)N膜层的膜基结合力仅为36N和28N。(Ti_x,Nb_1-x)N梯度涂层的膜基结合力达到了70N,但(Ti_x,Zr_1-x)N梯度膜的膜基结合力与均质膜相比没有明显改善,仅为37N。HIPIB辐照后,(Ti_0.35,Nb_0.65)N和(Ti_0.45,Nb_0.55)N膜层的膜基结合力分别提高到70N和65N,而(Ti_x,Nb_1-x)N梯度涂层的膜基结合力提高到78N。在简化的条件下,对HIPIB辐照过程的温度场进行了模拟,结果表明,HIPIB开始作用阶段,温度迅速上升,升温速率达10¹¹K/s,很快达到膜层材料的熔点,随后温度开始下降,降温速率达10¹⁰K/s。在整个辐照过程中,膜层表面始终有最大的温度分布,材料表层首先熔化,随后熔化深度向内层扩展,熔化深度为0.4μm左右。更多还原

【Abstract】 It is well recognized that wear constitutes one of the three major reasons responsible for the failure of mechanical components. The consumption of energy and raw materials resulted directly from the wear of mechanical components is very enormous and that would occupy nearly 40 percent of the total energy cost for the industrialization developed countries in the world. In this circumstance, great efforts have been paying to the improvement of material wear resistance, where methods based on surface coating technique exhibit essential potential for the enhancement of wear resistance. In the present work, hard coating techniques was firstly studied, then the effect of high intensity pulsed ion beam （HIPIB） irradiations was further investigated to explore their influence on the properties of wear resistance.The preparation of hard coatings was conducted on an arc ion plating equipment of type Bulat-6. On considering the different physical and chemical properties of elements including Nb, Zr and Cr, then adjusting arc currents on the separated pure metal targets, homogeneous coatings of different constituents, such as (Ti_0.35,Nb_0.65)N, (Ti_0.45,Nb_0.55)N, (Ti_0.47,Zr_0.53)N, (Ti_0.70,Zr_0.30)N, (Ti_0.62,Cr_0.38)N and (Ti_0.67,Cr_0.33)N, and also gradient coatings including (Ti_x,Nb_1-x)N and (Ti_x,Zr_1-x)N were successfully fabricated on high-speed steel substrates.The coating irradiation work was carried out on a HIPIB equipment of type TEMP-6 in State key laboratory for material modification by energetic beams of Dalian University of Technology. Under the device configurations of polymer anode, monopolar pulse mode and outer magnetically insulated ion diode design, the main ion species of ion beam are about 30 % Cⁿ⁺ and 70 % H⁺, the positive pulse used to accelerate ions is of 300-350 kV with a pulse width of 70 ns. In our experiments, the homogeneous coatings, （Ti,Nb）N, （Ti,Zr）N, and gradient coatings, (Ti_x,Nb_1-x)N, (Ti_x,Zr_1-x)N were irradiated with HIPIB beam current of 60A/cm²and 100 A/cm² separately.According to the scanning electron microscope （SEM） analysis results, when using HIPIB beam current of 60A/cm², micro-cracks were found on the irradiated surface for the samples of （Ti,Zr）N homogeneous coating and (Ti_x,Zr_1-x)N gradient coating. While for the （Ti,Nb）N homogeneous coating sample, the surface layer was melted partially accompanied by the morphologies of melt droplet and craters. The formation of melt droplet could be explained by the return of ablated materials back onto the irradiated surface. For the craters, it is suggested that the HIPIB irradiation could splash out particles located in the surface layer of coatings and leave structures in form of concave pit, and the fast cooling of surface melted layer gives no time for the recovery of these pits. For the samples irradiated with HIPIB of beam current 100 A/cm², micro-cracks were formed on all irradiated surfaces.The wear resistance measurement of coating samples before and after HIPIB irradiation were conducted on a friction and wear testing machine of type MM-200. It was found that before the HIPIB irradiation, the wear resistance of （Ti,Nb）N homogeneous coating is much better than that of （Ti,Zr）N coatings. When using load of 300N, the wear volumes of (Ti_0.35 ,Nb_0.65)N and (Ti_0.45 ,Nb_0.55)N coatings are 2.389 and 2.162×10^-3mm³, while for (Ti_0.47,Zr_0.53)N and (Ti_0.70,Zr_0.30)N coatings, they are 4.215 and 5.452×10^-3mm³. Increasing the load to 600N, the wear volumes of (Ti_0.35,Nb_0.65)N and (Ti_0.45,Nb_0.55)N coatings are 2.762 and 3.217×10^-3mm³, for (Ti_0.47, Zr_0.53)N and (Ti_0.70, Zr_0.30)N coatings, they are 6.855 and 8.468×10^-3mm³. Additionally, the wear resistance of gradient coatings (Ti_x,Nb_1-x)N is better than （Ti,Nb）N homogeneous coatings with wear volume of 1.514×10^-3mm³ under 300N, and 2.139×10^-3mm³ under 600N. While the wear resistance of (Ti_x,Zr_1-x)N gradient coatings are almost same as that of homogeneous coatings. After the HIPIB irradiation, the wear resistance of （Ti,Nb）N homogeneous coating exhibits significant improvement, and the wear volumes of load 300N decrease to 1.771 and 1.348×10^-3mm³ for the coating (Ti_0.35,Nb_0.65)N and (Ti_0.45,Nb_0.55)N, for the case of load 600N, they are 2.299 and 2.011×10^-3mm³ respectively. On the contrary, the wear resistance of (Ti_x,Nb_1-x)N gradient coatings decrease after the HIPIB irradiation. The wear volume increases to 2.179×10^-3mm³ for the load of 300N and 2.527×10^-3mm³for 600N. To explore the reasons for the influence of HIPIB irradiation on the wear resistance of hard coatings, the changes of microstructure, microhardness and coating-substrate adhesion occurring in the HIPIB irradiated samples were analyzed systematically.From the X-ray diffractometry analysis results, it was found that before the HIPIB irradiation, the （Ti,Nb）N homogeneous coating consists of a single （Ti,Nb）N phase with preferred orientation of （111） crystal plane, where the （Ti, Nb）N phase reserves the same face-centered cubic structure as TiN. And the （Ti,Zr）N homogeneous coating consists of four phases, i.e. （Ti,Zr）N, （Zr,Ti）N, TiN and ZrN, they have all the same structure as TiN. The structure of （Ti, Cr）N coatings consists of major phase （Ti,Cr）N and a small account of Cr₂N phase. For the gradient coatings, the (Ti_x,Nb_1-x)N coating is composed of mainly （Ti,Nb）N phase and some （Ti,Nb）2N, well the (Ti_x,Zr_1-x)N consists of still the same four phases as （Ti, Zr）N homogeneous coating. After the HIPIB irradiation, there is no change in phase composition for all kinds of hard coatings, no matter they are homogeneous or not.The microhardness of coatings before and after HIPIB irradiation was measured with a super-slight Knoop microhardness testing machine of type DMH-2LS. It was found that before the HIPIB irradiation, （Ti,Zr）N coating has the highest microhardness among the different kinds of homogenous coatings. The microhardness of (Ti_0.47,Zr_0.53)N coating is HK3678, and HK3509 for (Ti_0.70,Zr_0.30)N coating, and it is only HK2651 for (Ti_0.35,Nb_0.65)N coating. This result could be explained by the multi phase composition of （Ti,Zr）N homogeneous coatings. For the gradients coatings, (Ti_x,Nb_1-x)N exhibits the maximum microhardness of HK3807, and (Ti_x,Zr_1-x)N coating is HK3450, almost the same value as homogeneous coating. After the HIPIB irradiations, the microhardness of （Ti,Nb）N homogeneous coating was improved enormously, increasing from HK2651 to HK3054. The microhardness of (Ti_0.45,Nb_0.55N coating increased also from HK3200 to HK3422. These phenomena were related to the multiplication of dislocations in the modified coatings induced by HIPIB irradiations. Whereas the microhardness of (Ti_x,Nb_1-x)N gradient coatings decreased obviously from HK3807 to HK3338. The adhesion strength of coating samples before and after HIPIB irradiation were measured on a scratch testing system of type CSR-01. It was found that before the HIPIB irradiation, the adhesion strength of （Ti,Nb）N homogeneous coating is better than that of （Ti,Zr）N with the strength values of 65N and 59N for (Ti_0.35,Nb_0.65)N and (Ti_0.45,Nb_0.55)N coatings respectively, and they are only 36N and 28N for (Ti_0.47,Zr_0.53)N and (Ti_0.70,Zr_0.30)N coatings. The adhesion strength of (Ti_x,Nb_1-x)N gradient coatings attains 70N, but there is no great difference for (Ti_x,Zr_1-x)N coatings as compared with homogeneous coatings, only 37N. After the HIPIB irradiations, the adhesion strengths of (Ti_0.35,Nb_0.65)N and (Ti_0.45,Nb_0.55)N coatings increase to 70N and 65N, the adhesion strength of (Ti_x,Nb_1-x)N coating reaches 78N.To determine the thermal and mechanical actions induced by the HIPIB irradiation onto different hard coatings, the numerical simulation method was applied with suitable assumptions. According to our calculation results, the coatings will be heated quickly and reach their melting temperature in a very short time, then cooled down slowly after the HIPIB pulsed energy input. The melting occurs firstly at the surface part of coatings then propagates along the depth direction, and the thickness of melting layer is normally 0.4μm.更多还原