| 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 (Ti0.35,Nb0.65)N, (Ti0.45,Nb0.55)N, (Ti0.47,Zr0.53)N, (Ti0.70,Zr0.30)N, (Ti0.62,Cr0.38)N and (Ti0.67,Cr0.33)N, and also gradient coatings including (Tix,Nb1-x)N and (Tix,Zr1-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, (Tix,Nb1-x)N, (Tix,Zr1-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 (Tix,Zr1-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 (Ti0.35 ,Nb0.65)N and (Ti0.45 ,Nb0.55)N coatings are 2.389 and 2.162×10-3mm3, while for (Ti0.47,Zr0.53)N and (Ti0.70,Zr0.30)N coatings, they are 4.215 and 5.452×10-3mm3. Increasing the load to 600N, the wear volumes of (Ti0.35,Nb0.65)N and (Ti0.45,Nb0.55)N coatings are 2.762 and 3.217×10-3mm3, for (Ti0.47, Zr0.53)N and (Ti0.70, Zr0.30)N coatings, they are 6.855 and 8.468×10-3mm3. Additionally, the wear resistance of gradient coatings (Tix,Nb1-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 (Tix,Zr1-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 (Ti0.35,Nb0.65)N and (Ti0.45,Nb0.55)N, for the case of load 600N, they are 2.299 and 2.011×10-3mm3 respectively. On the contrary, the wear resistance of (Tix,Nb1-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 (Tix,Nb1-x)N coating is composed of mainly (Ti,Nb)N phase and some (Ti,Nb)2N, well the (Tix,Zr1-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 (Ti0.47,Zr0.53)N coating is HK3678, and HK3509 for (Ti0.70,Zr0.30)N coating, and it is only HK2651 for (Ti0.35,Nb0.65)N coating. This result could be explained by the multi phase composition of (Ti,Zr)N homogeneous coatings. For the gradients coatings, (Tix,Nb1-x)N exhibits the maximum microhardness of HK3807, and (Tix,Zr1-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 (Ti0.45,Nb0.55N 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 (Tix,Nb1-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 (Ti0.35,Nb0.65)N and (Ti0.45,Nb0.55)N coatings respectively, and they are only 36N and 28N for (Ti0.47,Zr0.53)N and (Ti0.70,Zr0.30)N coatings. The adhesion strength of (Tix,Nb1-x)N gradient coatings attains 70N, but there is no great difference for (Tix,Zr1-x)N coatings as compared with homogeneous coatings, only 37N. After the HIPIB irradiations, the adhesion strengths of (Ti0.35,Nb0.65)N and (Ti0.45,Nb0.55)N coatings increase to 70N and 65N, the adhesion strength of (Tix,Nb1-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.
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