Glow Plasma Surface Alloying Technique Research Articles

High-temperature oxidation behavior of double glow plasma Cr-Y alloyed layers on Ti2AlNb alloy

A Cr-Y alloyed layer was synthesized on the surface of Ti2AlNb by double glow plasma surface alloying technique. The morphology, phase composition and oxidation behaviors at 750 °C, 800 °C, and 850 °C of Cr-Y alloyed layers were systematically investigated. The results illustrated that Cr-Y alloyed layer was approximately 10 μm thick, which the morphology of alloyed layer was uniform and compact, with a flat and uniform interface to the matrix. Oxidation kinetics for the Cr-Y alloyed layer approximately followed the parabolic law, with an oxidation weight gain significantly lower than that of Ti2AlNb. The predominant oxides of Cr-Y layer were CrNbO4, Cr2O3, and Y2O3, which effectively hindered oxygen diffusion into the substrate.

Tribological behavior of diamond particles reinforced hafnium matrix composite coatings on Ti6Al4V

The diamond particles reinforced hafnium matrix composite coatings are prepared by the double glow plasma surface alloying technique combined with the microwave plasma chemical vapor deposition process (MPCVD). The effect of the Hf diffusion layers and diamond particles on their phase transformation, microstructure evolution, and wear behavior is systematically investigated. The results reveal that the surface of the Hf-alloying coating which is fabricated by plasma surface metallurgy emerged discrete micropores due to the Kirkendall effect during the plasma reverse sputtering. With the reverse sputtering time increasing, the general pore size increases, and the deposition layer has been completely sputtered out, leaving the Hf diffusion layer with a thickness of about 10 μm. After diamond particles deposition by MPCVD, the diamond particle reinforced hafnium matrix composite coatings with carbide and diamond coexisting were formed. The wear experiments were conducted in ambient air with a reciprocating friction tester, demonstrating that the diamond particle reinforced hafnium matrix composite coatings exhibited good antifriction performance with the decrease of wear rate by ∼8 times due to the lubrication effect of the diamond and graphite particles.

Effects of TiMoTa nano-crystalline interlayer on nucleation, adhesion and tribological behaviors of diamond coating

To investigate the influence of the transition layer on diamond nucleation and growth, the TiMoTa multi-alloy interlayers were firstly prepared on WC-6%Co cemented carbide by double glow plasma surface alloying technique, and diamond was then deposited using microwave plasma chemical vapor deposition system. The thickness of the TiMoTa interlayers increased from 1.2 μm to 2.7 μm with the deposition temperature increasing from 800 to 900 °C. Due to the formation of nano-crystalline structure and hard phase, the as-prepared TiMoTa interlayer exhibited high micro-hardness. In the diamond deposition process, the nano-carbide particles preferentially formed at the TiMoTa interlayers can effectively prevent the further diffusion of C, so the surface carbon concentration rapidly accumulates to the critical value required for the nucleation and growth of diamond microcrystals. Finally, a microscale wear-resistant diamond coating with good adhesion was grown on the transition layer, the crack propagation radius of the diamond coating is ∼162 μm, and can reach Hf 2–3 grade. Therefore, our prepared TiMoTa nano-crystalline interlayer provides a new path for the development of a high-quality diamond coating with good adhesion on cemented carbide.

The preparation and lubrication properties of a CrN/Cr multilayer using the double glow plasma surface alloying technique

Metal sealing rings with high hardness can improve wear resistance and reduce internal leakage. In this study, the double glow plasma surface alloying (DGPSA) technique was employed to produce the necessary conditions for a metallurgical bond and lubricant storage. Four primary stages are required in deposition processing: evaporation, destruction, atomization, and ionization. A Cr layer (including a 5 μm interdiffusion layer and a 45 μm pure metallic layer in thickness) and a thin (1–2 μm) CrN layer were prepared using the DGPSA technique. The obtained interdiffusion layer can reduce the mismatch in mechanical properties between the Cr layer and the substrate. When the atomic coverage of N atoms is higher than 1.5 ML, the stable adsorption structure is essentially nonexistent, indicating that improving the N2 ionization rate is more valuable than increasing the nitrogen partial pressure. When the Ar/N2 flow ratio is 2:1, the CrN/Cr multilayers provided microreservoirs for lubricants and improved wear and plastic deformation resistance. For the CrN/Cr multilayer, a higher contact pressure resulted in superior frictional properties.

Characterization and properties of NbN–Nb bilayer formed on titanium for bipolar plates

In this study, the NbN/Nb bilayer structure was prepared by duplex-treatment (plasma surface alloying + nitriding) on titanium used as bipolar plates for proton exchange membrane fuel cells (PEMFCs). Niobium coating was deposited on titanium by means of double glow plasma surface alloying technique. Then, a thin NbN layer was created by plasma nitriding. The corrosion resistance and electrical conductivity of samples were measured in simulated PEMFCs environments. The result shows that at an applied potential of 0.6 V the corrosion current density of duplex-treated sample is two orders lower than that of untreated titanium. After corrosion testing at 0.6 V for 4 h, the interfacial contact resistance is 5.1 mΩ cm2 compared with 29.7 mΩ cm2 for untreated titanium.

Characterization of Quasi-Static/Dynamic Contact Mechanical Properties of Mo Surface-Modified TC4

By using the double glow plasma surface alloying technique, a Mo surface-modified layer is prepared on Ti6Al4V(TC4). The element concentration and microstructure are characterized with a glow-discharge optical emission spectroscope and a scanning electron microscope. The results indicate that the Mo modified layer is compact in structure and gradation in composition, which consists of a pure Mo deposition layer and a thick Mo diffusion layer. Nanoindentation test results indicate that the surface hardness of TC4 is significantly improved after surface modification. Therefore, the initial part of the Mo diffusion layer has higher hardness than the Mo deposition layer. The impact tests for 10,000 cycles at different loads demonstrate that impact load 100 N only causes small plastic deformation, while impact loads 300 N and 500 N could result in cracks. Combining nanoindentation test with finite element reverse analysis, plastic parameters of the Mo modified layer are quantitatively determined. By using the impact test and finite element forward analysis, the dynamic contact mechanical properties of Mo surface-modified TC4 are characterized. When the impact cycles are fixed, ring cracks firstly occur and then radial cracks occur with the impact load increase on the graded layer. The ring cracks are mainly caused by impact stretch fatigue and corresponding cyclic stress is between 3.53 and 2.62 GPa. The radial cracks are mainly related to the tension-compression fatigue and corresponding cyclic stress is between 3.92 and −0.97 GPa.

Effects of plasma surface Ta alloying on the tribology behavior of γ-TiAl

To improve the wear resistance of ?-TiAl alloy, Ta alloy layer was prepared on surface by double glow plasma surface alloying technique. The tribology behavior of Ta alloy layer against Si3N4 at 25?, 350? and 500? were comparatively studied. The results showed that Ta alloy layer comprised a deposition layer and a diffusion layer. The deposition layer played a role in protection as a soft film. With the increase of temperature, the wear mechanism of ?-TiAl changed from abrasive wear to coexistence of abrasive wear and oxidation wear. Ta alloy layer?s wear mechanism changed from adhesive wear to coexistence of adhesive wear and oxidation wear. Surface Ta alloying process significantly reduced the wear volume, the specific wear rate and the friction coefficient of ?-TiAl and improved the wear resistance properties of ?-TiAl.

TRIBOLOGICAL AND CORROSION BEHAVIOR OF SiC/TaXC BILAYER COATINGS PREPARED ON STAINLESS STEEL SURFACE BY DOUBLE GLOW PLASMA SURFACE ALLOYING TECHNIQUE

In this work, SiC/TaxC bilayer coatings were prepared on stainless steel surface by double glow plasma surface alloying technique to improve the wear and corrosion resistance of the substrate. The effect of reaction temperature during the growth of SiC on the microstructure and property of the coating was investigated. The results showed that the surface topography of the coating could be regulated by the reaction temperature during the growth of SiC. Interactional flower-shaped rings, reticulate patterns, nanoparticles and microparticles were observed on the samples prepared at 750∘C, 800∘C, 850∘C and 900∘C, respectively. Tribological performance tests showed that the friction coefficient and specific wear rate of all the coated specimens were significantly decreased than the uncoated ones, indicating that the wear resistance of stainless steel was improved by the SiC/TaxC coating. The construction of the bilayer coating enhanced the corrosion resistance of stainless steel in terms of electrochemical tests. With an increase of the reaction temperature, the wear and corrosion resistance increased at first and then gradually decreased. SiC/TaxC coating prepared at 800∘C exhibited the best overall performance.

Tribological behavior of borocarburized layer on low-carbon steel treated by double glow plasma surface alloying

In this paper, the borocarburized layer was fabricated on the surface of low-carbon steel via double glow treatment to enhance the wear resistance. Benefited by the gradient structure of an outermost boride layer and inner carburized layer, the bonding strength of the protective coating was improved. The novel design improved the mechanical properties at the coating-substrate interface and extended the service life of the coating. The microstructure and composition of borocarburized layer were analyzed by SEM, XRD, XPS. The tribological properties of substrate and borocarburized layer under dry sliding against ZrO2 ball were investigated. The results indicated that borocarburized layer consisted of a 38 μm boride layer with main phase of Fe2B and a 75 μm carburized layer with main phase of Fe5C3. The microhardness of borocarburized layer emerged in gradient distribution attributed to the double glow plasma surface alloying technique, and the maximum value was around 1700 HV. In addition, the major wear mechanisms of low carbon steel were fatigue and abrasive wear, which transformed to abrasive and adhesive wear with the load increased. The wear mechanisms of borocarburized layer were abrasive and adhesive wear. During wear process, borocarburized layer with high hardness against ZrO2 ball due to the decreased real contact areas. Therefore, the borocarburized layer fabricated on low carbon steel enhanced the wear resistance effectively.

Effect of Ta diffusion layer on the adhesion properties of diamond coating on WC-Co substrate

To enhance diamond nucleation and adhesion on cemented carbide substrates, the Ta diffusion layers with gradient structure were deposited by the combination with double glow plasma surface alloying technique (DGPSA) and the reverse-sputtering process. The effect of reverse-sputtering times on phase composition and morphology of the Ta surface layers was studied. It was found that both the thickness of the Ta deposition layer and the amount of Ta elements decreased during the removal of the Ta deposition layer. With the reverse-sputtering time increases from 0 to 60 min, the thickness of the Ta deposition layers decreased from 1.6 μm to 0 μm. When the reverse-sputtering time reached 30 min, the as-prepared sample surface exhibited the maximum micro-hardness (3496.3 HV1.96N). Rockwell C indentation tests were used to investigate the effect of the Ta diffusion layers on the adhesion between the WC-Co substrate and the diamond coating. The results show that diamond coating exhibits good adhesion performance on WC-Co substrate with the Ta diffusion layer after reverse-sputtering for 60 min, indicating that the barrier effect of cobalt diffusion is enhanced by introducing the Ta diffusion layer.

DOUBLE GLOW PLASMA SURFACE TITANIZING ON AISI 316 STAINLESS STEEL WITH IMPROVED WEAR RESISTANCE: EFFECTS OF PROCESS PARAMETERS

Using the double glow plasma surface alloying technique, a titanizing coating with improved wear resistance can be prepared on AISI 316 stainless steel. The purpose of this paper is to investigate process parameter effects by orthogonal array design. Four main factors, titanizing temperature, holding time, voltage difference and electrode distance, are adopted in orthogonal experiments. For each factor, four levels are set. The range analysis is used to investigate the factor and level influences on the coating thickness and specific wear rate. Meanwhile, the analysis of variance method is applied to calculate the contributions of each factor. The results indicate that temperature is most critical. In balancing the coating thickness and the wear property, the optimal process parameters are 950∘C, 3[Formula: see text]h, 200[Formula: see text]V and 18[Formula: see text]mm. Corresponding to the optimal process, the thickness and the specific wear rate of the titanizing coating are 10[Formula: see text][Formula: see text]m and 2.609E−05 mm3⋅ N−1⋅ m−1, respectively.

MICROSTRUCTURE AND WEAR PROPERTY OF Ti/C MODIFIED LAYERS ON Ti–6Al–4V SUBSTRATE

The Ti/C modified layers were prepared on Ti–6Al–4V alloy by double glow plasma surface alloying technique. The microstructure and composition of the modified layers were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). The bonding strength, micro-hardness and friction performance of the modified layers were examined by the scratch tester, micro-hardness tester, reciprocating wear tester, and white light interferometer. The results show that both of the microstructure and properties of the Ti/C modified layer get the remarkable effects when the temperature reaches 910∘C. Belonging to metallurgical bonding with the substrate, the modified layer possesses a continuous, compact and uniform packet-like particle structure. Compared with the Ti–6Al–4V substrate, the surface micro-hardness and wear resistance of Ti/C modified layer are significantly improved.

Oxidation behaviour of plasma surface alloying on Ti6Al4V alloy

ABSTRACTTi–CrNi alloy coatings with 20, 40, 60 and 80 at-%Ni were prepared on Ti6Al4V alloy surface by double glow plasma surface alloying technique. The cyclic oxidation behaviour of the coatings was investigated at 750, 850 and 950°C. The results show that each coating has a complete structure of settled layer, mutual diffusion layer and sputtering affected zone. When the Ni content was 40 at-%, the Ti–CrNi alloy coating showed the best cyclic oxidation resistance. The oxide scale with ‘Cr2O3 film+NiO film’ structure showed the best resistance to peeling.

Microstructure and mechanical properties of Ti-6Al-4V alloy diffused with molybdenum and nickel by double glow plasma surface alloying technique

Ti-6Al-4V alloy substrates are diffused with molybdenum (Mo) and nickel (Ni), respectively, using the double glow (DG) plasma surface alloying technique. The crystal structures and surface morphologies of the diffused substrates are investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, the elemental compositions of the Mo- and Ni-diffusion modified surface layers are examined using an Auger electron spectrometer (AES) and an electron probe X-ray microanalyzer (EPMA). Finally, the hardness and wear resistance properties of the two surface layers are evaluated by means of Knoop hardness tests and pin-on-disk sliding tests, respectively. It is shown that the Mo-diffusion modified layer has a mixed Mo-Ti structure. By contrast, the Ni-diffusion modified layer consists of NiTi phase and Ni3Ti and NiTi2 intermetallic phases. Both surface alloying treatments increase the hardness of the Ti-6Al-4V substrate and improve the wear resistance as a result. Notably, the Ni-diffusion modified substrate has a higher friction coefficient than the Mo-diffusion modified substrate, but exhibits a lower wear rate. The improved wear resistance can be attributed to the presence of the NiTi, Ni3Ti and NiTi2 phases, which increase the yield strength of the contact surface and therefore reduce the wear mass.

Effect of plasma molybdenized buffer layer on adhesive properties of TiN film coated on Ti6Al4V alloy

Effect of molybdenized buffer layer on adhesion strength of TiN film on Ti6Al4V alloy was investigated. The buffer layer composed of a dense molybdenum deposition layer, a rapid drop zone and a slow fall zone was prepared using double glow plasma surface alloying technique. Scratch tests and low energy repeated impact tests were adopted to comparatively evaluate the duplex treated layers and the single TiN samples. The results show that the critical load was increased from 62N for the single TiN film to over 100N for the duplex treated layer. The volume of impact pit, formed in impact tests, of the single TiN samples is 9.15×106μm3, and about 1.5 times than that of the duplex treated samples. The Leeb hardness values reveal that about 70% impact energy was transferred to the single TiN samples to generate permanent deformation, while that was only about 47% for the duplex treated samples. The mechanism of improving adhesion strength is attributed to synergistic effect due to an inverted-S shape elastic modulus distribution produced by the molybdenized layer.

Design and synthesis of diffusion-modified HfC/HfC SiC bilayer system onto WC-Co substrate for adherent diamond deposition

Abstract A diffusion-modified HfC/HfC SiC bilayer system was innovatively designed and synthesized onto cemented carbide (WC-Co) substrate by reactive double glow plasma surface alloying (DGPSA) technique for adherent diamond deposition. The microstructure, phase composition and adhesion of the bilayer system were investigated, as well as its effect on the diamond coating system. The results showed that the bilayer system was made up of a 1.0-μm-thick nanostructured HfC-dominant inner layer and a 0.7-μm-thick HfC SiC mixed outer layer. As the gradient element distributions existed at the bilayer/substrate interface, the bilayer system displayed a superior adherence to the substrate. And the surface microhardness improved from 1802 HV0.1 to 2857 HV0.1 after the reactive DGPSA treatment. Subsequently, a uniform and dense nanocrystalline diamond coating with thickness of 4.0 μm was successfully deposited onto the HfC/HfC SiC interlayered substrate. Benefit from the effective suppression of Co diffusion by the interlayer and the reasonable design in its hardness and thermal expansion coefficient (TEC), the obtained diamond coating possessed an excellent adhesion. Therefore, the diffusion-modified HfC/HfC SiC bilayer systems synthesized via reactive DGPSA technique can be considered as a novel interlayer option for depositing adherent diamond coatings on WC–Co substrates.

Wear and corrosion properties of Mo surface-modified layer in TiNi alloy prepared by plasma surface alloying

In order to improve the wear resistance and restrain nickel release of TiNi alloys, the Mo modified layers on TiNi substrates were obtained using the double glow plasma surface alloying technique. Scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD) were employed to investigate the morphology, composition and structure. Microhardness test and scratch test were performed to analyze the microhardness and coating/substrate adhesion. Tribological and electrochemical behaviors of the Mo modified layers on TiNi were tested by the reciprocating wear instrument and electrochemical measurement system. The Ni concentrations in Hanks’ solution where surface electrochemical tests took place were measured by mass spectrometry. The surface-modified layer contained a Mo deposition layer and a Mo diffusion layer. The X-ray diffraction analysis revealed that the modified layers were composed of Mo, MoTi, MoNi, and Ti2Ni. The microhardnesses of the Mo modified layers treated at 900 °C and 950 °C were 832.8 HV and 762.4 HV, respectively, which was about 3 times the microhardness of the TiNi substrate. Scratch tests indicated that the modified layers possessed good adhesion with the substrate. Compared with as-received TiNi alloy, the modified alloys exhibited significant improvement of wear resistance against Si3N4 with low normal loads during the sliding tests. Mass spectrometry displayed that the Mo alloy layers had successfully inhibited the Ni release into the body.

Corrosion property of copperized layer on Zr formed by double glow plasma surface alloying technique

Zr and its alloys have excellent mechanical properties as new structural material, but in specific application environment, its corrosion resistance still needs to be further explored. In this work, double glow plasma surface alloying technique was used for copperizing on pure Zr surface. Besides, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersion spectrum (EDS) were employed to characterize the samples. Furthermore, research was also conducted on the polarization curve of the samples in different solutions. Copperizing on surface can improve corrosion resistance of pure Zr in 3.5 % NaCl and 0.5 mol·L−1 NaOH solutions. Especially in 0.5 mol·L−1 NaOH solution, the corrosion resistance can achieve significant improvement. However, copperizing has no influence on the improvement of corrosion resistance of pure Zr in 0.5 mol·L−1 H2SO4 solution. The results may provide new insight into way for improving the corrosion property of zirconium alloys.

Study on Titanized Layer Microstructure of T10 Steel by Double Glow Plasma Surface Alloying Technique

The titanized layer was prepared on the surface of T10 steel using a double glow plasma surface alloying (DGPSA) technique. The titanized layer was characterized by SEM and scratch tester. Results showed that the TiC layer with a thickness of 1.5~8.5μm was formed on the sample surface at the range of 900°C to 1100°C for the holding time from 2h to 6h, which was homogeneous, dense, and metallurgically combined with the substrate. The Ti concentration gradually decreased from surface to the matrix. The diffusion activation energy of Ti during double glow plasma titanizing was also estimated.

Plasma surface Cu alloyed layer as a lubricant on stainless steel sheet: Wear characteristics and on-job performance in incremental forming

To solve the problems of poor forming and easy adhesion of the stainless steel, Cu alloyed layer on the stainless steels was prepared by the double glow plasma surface alloying technique. The experimental results indicated that the supersaturated copper dispersedly precipitated in grain interior and crystal boundaries and formed the vermicular structure. The tribological tests indicated that the friction coefficient of the Cu alloyed layer was lower than that of the stainless steels. The wear rate of stainless steel in the presence of Cu alloyed layer was approximately 2-fold lower than that in the absence of the alloyed layer. The results of the incremental forming indicated that the ploughing phenomenon was not observed on the stainless steel in the presence of Cu alloyed layer during the incremental forming, while the stainless steel presented the deep ploughing. Therefore, Cu alloyed layer on stainless steel exhibited excellent self-lubrication and forming properties.