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shows XRD patterns of the coated samples. It can be con¯rmed that PIRAC produced titanium nitride is TiN and Ti 2 N, in which Ti 2 N is the main phase. Phase composition of those samples coated by PVD di®ers from those of PIRAC. The TiN with a preferred orientation of (111) is the main phase for the PVD coating, accompanied by a spot of Ti 2 N. Figure 2 shows typical atomic concentration pro¯les across the nitriding di®usion zone of the polished cross-section of the coated samples obtained using EDS by points line scan. From Fig. 2, it can be seen that atomic percent of nitrogen of PIRAC coatings
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In the present work, hardness and elastic modulus of a titanium nitride coatings prepared on Ti6Al4V by powder immersion reaction-assisted coating (PIRAC) are tested and comparatively studied with a physical vapor deposition (PVD) TiN coating. Surface hardness of the PIRAC coatings is about 11GPa, much lower than that of PVD coating of 22GPa. The h...
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... Recently, the attention of scientists has been drawn to diffusion boride layers, which have higher hardness than nitride ones (35 GPa for TiB 2 [28] and 21 GPa for TiB [29] vs. 24 GPa for TiN [30]). Therefore, they allow expected higher wear resistance compared with nitride layers, which indicates the prospect of using boride layers in medical tribocouples. ...
The surface characteristics and friction behaviour of titanium Grade 2 with modified nitride (TiN, Ti2N) and boride (TiB) compound layers were investigated. It was shown that during non-contact boriding in oxygen-containing medium of titanium, the diffusion processes take place mainly by the interscale mechanism; however, during nitriding, besides the traditional interscale diffusion mechanism, the grain boundary mechanism of diffusion of nitrogen atoms is also realized. The optimal set of surface roughness parameters (height and step parameters, a combination of kurtosis and asymmetry, and profile reference curve parameters) was obtained after boriding. It was determined that the intensity of the adhesive wear of the tribo-pairs with stainless steel and ultrahigh molecular weight polyethylene under dry sliding conditions was influenced not only by the hardness but also roughness of the modified surface layer. The lowest friction coefficient was fixed for the TiB compound layer in both tribo-pairs.
... At the PIRAC titanisation stage, substrates are immersed into Ti powders and treated at 900-1000°C for 30 min to make them homogenous covered with a Ti-rich layer. As PIRAC treated at 800°C for 8 h is favourable for TiN formation on Ti substrate to avoid grain coarsening and better hardness [19]. At the followed PIRAC nitriding stage, the PIRAC titanised samples are immersed in Cr 2 N powder and treated at 800°C for 8 h. ...
... The hardness of the present prepared porous PIRAC TiN coating is lower than that of the dense PIRAC TiN coating prepared on Ti [19]. The PIRAC TiN coatings from niriding of titanium are composed of TiN, Ti 2 N and Ti(N) solid solution, in which the content of Ti (N) solid solution is the highest [19,21]. ...
... The hardness of the present prepared porous PIRAC TiN coating is lower than that of the dense PIRAC TiN coating prepared on Ti [19]. The PIRAC TiN coatings from niriding of titanium are composed of TiN, Ti 2 N and Ti(N) solid solution, in which the content of Ti (N) solid solution is the highest [19,21]. The hardness of TiN, Ti 2 N and Ti(N) solid solution is about 25, 15-22 and 10 GPa [23][24][25]. ...
Porous titanium nitride coatings are prepared on 310 stainless steel by the powder immersion reaction-assisted coating (PIRAC) titanisation-nitriding process. For titanisation below 950°C for 30 min, the detected phases on 310 steel are FeTi, Fe2Ti and TiN. Titanisation at 1000°C for 30 min, the detected phases on 310 steel are FeTi, Fe2Ti, TiN and Ti. After further nitriding at 800°C for 8 h, titanium nitride coating composed of TiN, Ti2N and TiN0.3 can be formed. Pore size and porosity of the prepared coating are decreased with increasing titanisation temperature, while the uniformity of the pores in the coating and hardness of the coating is increased with increasing titanisation temperature. Microhardness of the porous PIRAC TiN coating prepared by titanisation at 900°C + nitriding at 800 °C, titanisation at 950°C + nitriding at 800 °C and titanisation at 1000°C + nitriding at 800°C is 8.65, 8.98 and 9.66 GPa, respectively.
采用粉末埋入反应辅助涂层（PIRAC）钛化-氮化工艺在310不锈钢表面制备了多孔氮化钛涂层。在950℃以下进行30分钟的钛化，310钢上检测到的物相为FeTi、Fe2Ti和TiN。在1000℃下进行30分钟的钛化，310钢上检测到的物相为FeTi、Fe2Ti、TiN和Ti。在800℃下进一步氮化8小时后，氮化钛涂层由TiN、Ti2N和TiN组成。制备的涂层孔径和孔隙率随钛化温度的升高而减小，而涂层中孔隙的均匀性和涂层的硬度随钛化温度的升高而增大。通过900°C钛化+800°C氮化、950°C钛化+800°C氮化和1000°C钛化+800°C氮化制备的多孔PIRAC TiN涂层的显微硬度分别为8.65 GPa、8.98 GPa和9.66 GPa。
This paper presents the results of the influence of variation of the synthesis conditions of CuBi/CuBi2O4 films with a change in the applied potential difference, as well as a change in electrolyte solutions (in the case of adding cobalt or nickel sulfates to the electrolyte solution) on changes in the phase composition, structural parameters and strength characteristics of films obtained using the electrochemical deposition method. During the experiments, it was found that, in the case of the addition of cobalt or nickel to the electrolyte solutions, the formation of films with a spinel-type tetragonal CuBi2O4 phase is observed. In this case, a growth in the applied potential difference leads to the substitution of copper with cobalt (nickel), which in turn leads to an increase in the structural ordering degree. It should be noted that, during the formation of CuBi/CuBi2O4 films from solution–electrolyte №1, the formation of the CuBi2O4 phase is observed only with an applied potential difference of 4.0 V, while the addition of cobalt or nickel sulfates to the electrolyte solution results in the formation of the tetragonal CuBi2O4 phase over the entire range of the applied potential difference (from 2.0 to 4.0 V). Studies have been carried out on the strength and tribological characteristics of synthesized films depending on the conditions of their production. It has been established that the addition of cobalt or nickel sulfates to electrolyte solutions leads to an increase in the strength of the resulting films from 20 to 80%, depending on the production conditions (with variations in the applied potential difference). During the studies, it was established that substitution of copper with cobalt or nickel in the composition of CuBi2O4 films results in a rise in the shielding efficiency of low-energy gamma radiation by 3.0–4.0 times in comparison with copper films, and 1.5–2.0 times for high-energy gamma rays, in which case the decrease in efficiency is due to differences in the mechanisms of interaction of gamma quanta, as well as the occurrence of secondary radiation as a result of the formation of electron–positron pairs and the Compton effect.
In this study, high-temperature nitriding was used to improve the surface hardness and wear resistance of Co–27Cr–22Fe alloy in a thermogravimetric analyzer. The high-temperature nitriding treatments were performed at 1200 °C for 3 and 10 h. Subsequently, at room temperature, the dry sliding wear test was carried out, and the possible effects of load on friction performance and microstructure of different specimens were investigated. The results show that the microstructure of as-received specimens is composed of γ-Co and MC carbides, while the microstructure of the nitrided specimens contains γ-Co, MC carbides, acicular AlN, and granular (Ti, Nb)N. The thickness of the nitriding layer is 375 μm and 708 μm for nitriding 3 h and nitriding 10 h, respectively. An improvement in microhardness (∼425 HV) was attained for nitrided specimens. For the as-received specimens, the wear rate decreases with increasing load. The as-received specimen exhibits better wear resistance than the nitrided specimen under a high load (∼30 N). The wear mechanism under different loads was mainly abrasive wear, accompanied by adhesive wear. For the nitrided specimens, the specimens show different wear mechanisms under varying loads. Under low load (∼5 N and ∼15 N), the high-temperature nitriding improves the wear resistance, and it exhibits abrasive wear and oxidative wear. Under high load (∼30 N), the wear resistance of the nitrided specimen was significantly reduced, and the wear mechanism is mainly abrasive wear, fatigue wear, and oxidative wear.
Multilayer coatings with individual layer thickness on the nanoscale exhibit superior mechanical properties because of their high interface density. However, compared to artificial phase interfaces, planar defects like twin and stacking faults (SFs) are hardly investigated in ceramic multilayer systems. We choose to combine the group VB transition metal nitride (TMN) TaN with its extremely low stacking faults energy (SFE) and TiN to form a superlattice (SL). TiN/TaN multilayers with a bilayer period (Λ) from 8 nm to 100 nm were prepared by dc magnetron sputtering. These as-deposited films show a peak hardness 36 ± 2.4 GPa at Λ=20 nm. The extensive high-resolution transmission electron microscopy (HRTEM) observations reveal that the dissociation of full dislocations results in the network of SFs and the formation of Lomer-Cottrell lock arrays inside the TaN layer. Meanwhile, further dislocation analysis indicated the Shockley partials cross slip at the interface. These findings provide us with a new perspective for designing TMN multilayers with planar defects.
The accuracy in the determination of the mechanical properties by instrumented indentation strongly depends on the indenter/material contact area, the corrective compliance, and the indenter tip defect. For the calibration, we suggest to combine 3 functions: (i) a Force-function, where only the corrective compliance term is the unknown parameter, (ii) an Area-function, allowing the estimation of the tip defect knowing the corrective compliance, and finally (iii) a Martens-function, to determine the Martens hardness. The proposed methodology is validated on a series of experiments performed between 2006 and 2015 on ceramics and metals using the same indentation instrument and the same Vickers indenter having undergone different blunts. As a main result, the Young’s moduli are found very close to that available in literature if a β-factor is introduced into the Area-function and Force-function. In addition, both the instrumented hardness and Martens hardness do not vary with the indentation force.Graphical abstract
Low wear resistance and high coefficient of friction of the Ti-6Al-4 V alloy surface limits its application in situations requiring tribological participation of the alloy. In the present study, a laser clad layer, formed by laser melting of a preplaced powder mixture (Al, TiO2, TiB2, TiN, and h-BN), had been applied on the Ti-6Al-4 V alloy substrate surface to improve its mechanical and tribological properties. The microstructure, phase composition, hardness, wear properties, and scratch-resistance of the coatings were analyzed using a scanning electron microscope (SEM), X-ray diffraction (XRD), Vickers micro-hardness test, ball-on-disk wear test, and scratch indentation test, respectively. A multi-objective optimization technique was implemented to solve a multi-objective optimization problem for the determination of preferred powder composition and optimum process parameters. The optimization result showed that higher values of coating thickness and higher degree of uniformity in microstructure were obtained in the case of laser cladding carried out at a higher value of laser power-to-scan speed ratio. The formation of ceramic phases such as TiB2 and TiN reinforced with Al2O3 particles helped increase the hardness and wear resistance by four fold and two fold, respectively. The presence of partially reacted h-BN particles in the Ti-rich coating matrix helped reduce the friction coefficient by a factor of two-third. Hence, the composite ceramic coating of Al2O3-TiB2-TiN-BN on Ti-6Al-4 V alloy may be considered suitable for tribo-mechanical applications.
The fracture strength of titanium nitride coatings prepared on Ti6Al4V by powder immersion reaction-assisted coating (PIRAC) at 700°C for different processing times has been studied. First, the fracture strength estimation expression was developed based on experimental bending phenomena and deformation analysis, as well as by considering the difference of the mechanical properties of the substrate and titanium nitride coating. The results showed that the fracture strength of the prepared PIRAC titanium nitride coatings increased with increasing processing times. The fracture strengths of the PIRAC titanium nitride coatings prepared at 700°C for 24 h, 48 h, 96 h, and 144 h were about 492.3 MPa, 546.6 MPa, 576.5 MPa, and 729.3 MPa, respectively. Further analysis indicated that such increments of the fracture strength of the coating resulted from the variation in composition, especially, the contents of TiN and Ti2N with higher mechanical properties increased with increasing processing time.
针对现有研究对涂层拉伸强度测试手段要求高，特别是缺少原位自生涂层，特别是多元多层涂层拉伸强度的适宜测量方法。现有本文研究了在700ºC温度下，通过粉末埋入反应辅助涂层（PIRAC）在Ti6Al4V上制备的氮化钛涂层在不同处理时间下的断裂强度。首先，基于弯曲实验现象、变形分析以及考虑基体和氮化钛涂层力学性能的差异，建立了断裂强度估算表达式。结果表明，随着处理次数的增加，制备的氮化钛涂层的断裂强度增加。在700℃下制备24、48、96和144小时的PIRAC氮化钛涂层的断裂强度分别约为492.3、546.6、576.5和729.3 MPa。进一步分析表明，涂层断裂强度的提高是由成分变化引起的，尤其是力学性能较高的TiN和Ti2N含量随着加工时间的增加而增加。
To give a deep insight into the nitrogen transfer mechanism during laser solid-state surface modification on titanium alloy, laser nitridation was conducted on Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy (TC11) without melting the metal surface. Microstructure characterizations of nitride layer formed under solid state condition were detailedly explored and the formation process of TiN phase was carefully discussed based on the lattice transformation. Results indicate that the nitride layer forming within a few seconds is composed of TiN phase layer and α phase layer with an orientation relationship: (11¯1)TiN // (0001)α, [011]TiN // [211¯0]α. Formation of TiN phase experiences fast solid-state transformation from α phase. Phase transformation from α-Ti lattice to TiN lattice experiences orthorhombic lattice transformation due to the shear deformation caused by rapid interstitial solution of nitrogen. After repeated laser nitridation process upon three times, nitride layer was thickened with an improved hardness of 824 HV. Linearly reciprocating ball-on-plane wear tests indicate that wear resistance of laser nitridation samples could be enhanced by a factor of 13.
Nimonic 75 sheets were cold-spun under different processing conditions and then heat-treated. The microstructure evolutions occurring during the process were studied and discussed in details. The results obtained showed the feasibility of the process when adopting low values of the tool feed rate. Metal spinning produces a deformed microstructure, different in the several areas of interest of the final component. The chosen heat treatment promoted the annealing of the material across the whole part.
