Double Glow Plasma Research Articles

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.

Oxidation Behavior of TiAl-Based Alloy Modified by Double-Glow Plasma Surface Alloying with Cr–Mo

AbstractA Cr–Mo alloyed layer was prepared on a TiAl-based alloy using plasma surface alloying technique. The isothermal oxidation kinetics of the untreated and treated samples was examined at 850 °C. The microstructure and phase composition of the alloyed layer were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray powder diffraction (XRD). The morphology and constituent of the oxide scales were also analyzed. The results indicated that the oxidation resistance of TiAl was improved significantly after the alloying treatment. The oxide scale eventually became a mixture of Al2O3, Cr2O3 and TiO2. The oxide scale was dense and integrated throughout the oxidation process. The improvement was mainly owing to the enhancing of scale adhesion and the preferential oxidation of aluminum brought by the alloying effect for TiAl-based alloy.

SURFACE Nb-ALLOYING ON 0.4C–13Cr STAINLESS STEEL: MICROSTRUCTURE AND TRIBOLOGICAL BEHAVIOR

0.4C–13Cr stainless steel was alloyed with niobium using double glow plasma surface alloying and tribological properties of Nb-alloyed steel such as hardness, friction and wear were measured. Effects of the alloying temperature on microstructure and the tribological behavior of the alloyed steel were investigated compared with untreated steel. Formation mechanisms of Nb-alloyed layers and increased wear resistance were also studied. The result shows that after surface Nb-alloying treatment, the 0.4C–13Cr steel exhibits a diffusion adhesion at the alloyed layer/substrate interface and improved tribological property. The friction coefficient of Nb-alloyed steel is decreased by about 0.3–0.45 and the wear rate after Nb-alloying is only 2–5% of untreated steel.

Double glow plasma carburization on zirconium to improve surface hardness and wear resistance

Though some important progress in the excellent mechanical properties of zirconium alloys have been reported, their high surface hardness and good wear properties need to be explored further. In this work, a carburized layer was formed on the surface of commercially pure zirconium by a double glow plasma hydrogen-free carburizing technique. Commercial high-purity graphite was used as the carbon source material. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Vickers hardness test, friction and wear test were used to characterize the samples carburized. The carburized layer could be clearly observed under a microscope. XRD patterns indicate that the zirconium carbide phase is formed in the carburized layer. The surface hardness of the sample increases significantly after carburization. Friction and wear tests results show that wear resistance and friction coefficient of zirconium are improved considerably after carburization. Surface plastic deformation is arrested to a low extent in contrast with pure zirconium because of the presence of ZrC phases during the wear test. The results may provide new insight into methods for surface strengthening of zirconium alloys. A carburized layer was formed on the surface of commercially pure zirconium by a double glow plasma hydrogen-free carburizing technique. The carburized layer could be clearly observed under a microscope. X-ray diffraction (XRD) patterns indicate that the zirconium carbide phase is formed in the carburized layer. The surface hardness of the sample increases significantly after carburization. Friction and wear tests results show that wear resistance and friction coefficient of zirconium are improved considerably after carburization .

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.

The Prediction of Double Glow Plasma Alloying Process Based on Improved Generalized Regression Neural Network

The Prediction of Double Glow Plasma Alloying Process Based on Improved Generalized Regression Neural Network

Wear resistance of TiN(Ti2N)/Ti composite layer formed on C17200 alloy by plasma surface Ti-alloying and nitriding

The duplex treatment of plasma Ti-alloying and plasma nitriding was applied on the surface of C17200 alloy to improve its wear resistance. C17200 substrate was alloyed with Ti using double glow plasma alloying to form a Ti-alloyed layer in its surface, and then treated by plasma nitriding to make a TiN(Ti2N) alloying layer based on the Ti-alloyed surface. The microstructure and formation mechanism were studied by using GDOES, XRD and SEM. The hardness, tribological property and electrical conductivity of C17200 alloy after plasma alloying and nitriding were investigated by mean of micro-hardness tester, friction and wear testers as well as impedance analyzers. Modulus of elasticity and the adhesive strength of TiN(Ti2N)/Ti composite layer were evaluated by nano-indenter and scratch tester. The result shows that a TiN(Ti2N)-Ti-Be-Cu composite layer with a thickness of 27μm is formed in the C17200 surface and is mainly composed of TiN, Ti2N, Cu(Ti) solid solution, etc. The composite alloying surface consists of the hard TiN(Ti2N)-rich layer on the top surface and Ti-Cu-Be diffusion layer, showing a strong adhesive strength with the C17200 substrate and a little decrease in the modulus of elasticity. A certain amount of Cu and Be together with TiN/Ti2N exists in the outmost, resulting in a better combination of wear resistance and conductive performance.

Micropore formation mechanism in iridium coating after high‐temperature treatment

Noble metal iridium is of great interest for high‐temperature applications and extreme environments. A high (110)‐oriented iridium coating was prepared by a double glow plasma process on the surface of niobium substrate. The morphology and composition of the coating were determined by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy, respectively. The phase of the coating was identified by X‐ray diffraction analysis. The misorientation angle distributions of grains on the surface and cross section of the coating were characterized by electron backscatter diffraction system. The uniform and pure iridium coating consisted of the submicrometer‐sized columnar grains with high‐angle boundary. The mean misorientation angles on the surface and cross section of the coating were 38.6° and 45.6°, respectively. After high‐temperature treatment, the coating was composed of equiaxed grains with distinct grain boundaries. Micropores appeared on the fracture surface of the coating. The micropore formation mechanism in Ir coating after high‐temperature treatment was investigated. Copyright © 2016 John Wiley & Sons, Ltd.

Zr/ZrC modified layer formed on AISI 440B stainless steel by plasma Zr-alloying

The surface Zr/ZrC gradient alloying layer was prepared by double glow plasma surface alloying technique to increase the surface hardness and wear resistance of AISI 440B stainless steel. The microstructure of the Zr/ZrC alloying layer formed at different alloying temperatures and times as well as its formation mechanism were discussed by using scanning electron microscopy, glow discharge optical emission spectrum, X-ray diffraction and X-ray photoelectron spectroscopy. The adhesive strength, hardness and tribological property of the Zr/ZrC alloying layer were also evaluated in the paper. The alloying surface consists of the Zr-top layer and ZrC-subsurface layer which adheres strongly to the AISI 440B steel substrate. The thickness of the Zr/ZrC alloying layer increases gradually from 16μm to 23μm with alloying temperature elevated from 900°C to 1000°C. With alloying time from 0.5h to 4h, the alloyed depth increases from 3μm to 30μm, and the ZrC-rich alloyed thickness vs time is basically parabola at temperature of 1000°C. Both the hardness and wear resistance of the Zr/ZrC alloying layer obviously increase compared with untreated AISI 440B steel.

Ablation behavior of monolayer and multilayer Ir coatings under carburizing and oxidizing oxyacetylene flames

Iridium is one of the most promising candidates for protective barrier of refractory materials to endure high service temperature. The multilayer iridium coating was produced by a double glow plasma process on the polished tungsten carbide substrates, compared with monolayer. The ablation behaviors of the monolayer on the unpolished and polished substrates were investigated under carburizing and oxidizing oxyacetylene flames, respectively, at the same time the multilayer coating ablated under oxidizing flames. Multilayer coating was a polycrystalline phase with the preferential (220) orientation. Monolayer on the unpolished substrate had fine coarse grains and some small microcracks were present. Multilayer consisted of columnar grains with some voids between the grains boundaries. The formation of a WIr phase in the as-deposited multilayer was attributed to high deposition temperature. The monolayer could endure high temperature up to 1800°C in carburizing flame. The substrates could be protected more effectively by multilayer than monolayer at 2000- 2200°C in oxidizing flame.

ON THE USE OF Mo/Mo2C GRADIENT INTERLAYERS IN DIAMOND DEPOSITION ONTO CEMENTED CARBIDE SUBSTRATES

Molybdenum/molybdenum carbide (Mo/Mo2C) gradient interlayers were prepared via double glow plasma surface alloying (DGPSA) technique onto cemented carbide (WC–Co) substrates for diamond deposition. The morphologies, phase composition and adhesion of the interlayers were investigated, as well as their effect on the subsequent diamond deposition. The results indicated that the Mo/Mo2C gradient interlayer deposited on WC–Co substrate was composed of 4.0-[Formula: see text]m-thick diffusion layer and 2.7-[Formula: see text]m-thick deposition layer. The Mo concentration decreased gradually with the depth direction whereas the Co and W concentrations increased. As a result, the Co binder phase was completely restricted within the substrate by the diffusion layer. The presence of gradient diffusion layer ensured excellent adhesion of the interlayer. Subsequently, nanocrystalline diamond coatings with excellent adhesion were deposited on the interlayered substrates. Thus, the Mo/Mo2C gradient interlayers deposited via DGPSA technique were demonstrated as a novel option for depositing adherent diamond coatings on WC–Co substrates.

Improving tribological properties of Ti-5Zr-3Sn-5Mo-15Nb alloy by double glow plasma surface alloying

Molybdenum, an alloying element, was deposited and diffused on Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate by double glow plasma surface alloying technology at 900, 950 and 1000°C. The microstructure, composition distribution and micro-hardness of the Mo modified layers were analyzed. Contact angles on deionized water and wear behaviors of the samples against corundum balls in simulated human body fluids were investigated. Results show that the surface microhardness is significantly enhanced after alloying and increases with treated temperature rising, and the contact angles are lowered to some extent. More importantly, compared to as-received TLM alloy, the Mo modified samples, especially the one treated at 1000°C, exhibit the significant improvement of tribological properties in reciprocating wear tests, with lower specific wear rate and friction coefficient. To conclude, Mo alloying treatment is an effective approach to obtain excellent comprehensive properties including optimal wear resistance and improved wettability, which ensure the lasting and safety application for titanium alloys as the biomedical implants.

Niobium coated Ti-Al alloy: improvement of tribological behaviour, oxidation resistance and flame retardancy

Double glow plasma (DGP) coatings were recommended for metallic components to mitigate the damage induced by complex working conditions. In this paper, A Ti-Al alloy was coated with niobium (Nb) via a DGP process to enhance its anti-oxidation properties, wear resistance and flame retardancy. The results showed that the Nb-coated Ti-Al alloy mainly comprised Nb, AlNb2, AlMoTi2 and β-Ti phases. Room temperature sliding-friction tests indicated that the Nb-coated Ti-Al alloy exhibited a stable friction coefficient of an average value of 0.25, whilst the same value for via the uncoated Ti-Al alloy was around 0.45. High-temperature oxidation tests revealed compact oxide grains without cracks after the 100 h test, indicating good oxidation resistance. An ablation test showed that the Nb-coated Ti-Al alloy exhibited excellent flame retardancy, with the ablation time of the Nb-coated Ti-Al alloy at 1.62 times that of the uncoated Ti-Al base alloy. The alloys tribological behaviour, oxidation resistance and flame retardancy mechanisms are discussed in detail in this paper.

Niobium coated Ti-Al alloy: improvement of tribological behaviour, oxidation resistance and flame retardancy

Double glow plasma (DGP) coatings were recommended for metallic components to mitigate the damage induced by complex working conditions. In this paper, A Ti-Al alloy was coated with niobium (Nb) via a DGP process to enhance its anti-oxidation properties, wear resistance and flame retardancy. The results showed that the Nb-coated Ti-Al alloy mainly comprised Nb, AlNb2, AlMoTi2 and β-Ti phases. Room temperature sliding-friction tests indicated that the Nb-coated Ti-Al alloy exhibited a stable friction coefficient of an average value of 0.25, whilst the same value for via the uncoated Ti-Al alloy was around 0.45. High-temperature oxidation tests revealed compact oxide grains without cracks after the 100 h test, indicating good oxidation resistance. An ablation test showed that the Nb-coated Ti-Al alloy exhibited excellent flame retardancy, with the ablation time of the Nb-coated Ti-Al alloy at 1.62 times that of the uncoated Ti-Al base alloy. The alloys tribological behaviour, oxidation resistance and flame retardancy mechanisms are discussed in detail in this paper.

Effects of elements W and C on microstructure and wear property of γ-TiAl surface alloying layer

To solve the poor tribological property of the γ-TiAl alloy, the duplex treatment of plasma carburisation on plasma alloying γ-TiAl with tungsten was conducted by double glow plasma surface alloying technique. The results indicated the alloying layer consisted of TiC and W2C phase, metallurgically adhered to the substrate. In terms of the H/E and H3/E2 ratios, the duplex treated specimen was nearly three times larger than the untreated specimen. The wear property of the specimens was tested on a pin-on-disk tribometer by rubbing against Si3N4 ceramic ball. The wear rate of the duplex-treated specimens is 1·056×10−4 mm3 N−1 m−1, which is only 25·9% of that of the untreated specimens. The relationship between alloying layer mechanical property and wear resistance indicates that the carbide phase formed within the alloying layer contributes to the improvement of the wear performance.

Tribological behaviors of Fe–Al–Cr–Nb alloyed layer deposited on 45 steel via double glow plasma surface metallurgy technique

Double glow plasma surface metallurgy technique was used to fabricate a Fe–Al–Cr–Nb alloyed layer onto the surface of the 45 steel. The microstructures and composition of the Fe–Al–Cr–Nb alloyed layer were analyzed by scanning electronic microscopy, X-ray diffraction and energy dispersive spectroscopy. The results indicate that the 20 μm alloyed layer is homogeneous and compact. The alloyed elements exhibit a gradient distribution along the cross section. Microhardness and nanoindentation tests imply that the surface hardness of the alloyed layer reaches HV 580, which is almost 2.8 times that of the substrate. Compared with the substrate, the alloyed layer has a much smaller displacement and a larger elastic modulus. According to the friction and wear tests at room temperature, the Fe–Al–Cr–Nb alloyed layer has lower friction coefficient and less wear mass, implying that the Fe–Al–Cr–Nb alloyed layer can effectively improve the surface hardness and wear resistance of the substrate.

Preparation and high-temperature oxidation behavior of plasma Cr–Ni alloying on Ti6Al4V alloy based on double glow plasma surface metallurgy technology

To improve the oxidation resistance of Ti6Al4V alloy, it was coated with a Cr–Ni alloy with 20, 40, 60, and 80at.% Ni content using the double-glow plasma surface metallurgy technology. The coatings were dense, uniform, and compact, including a complete structure of deposited layer, interdiffusion layer, and sputtering-affected zone. The effect of Ni content on the isothermal oxidation behavior of coating was investigated at 750, 850, and 950°C. The results show that the oxide scale consisted of NiO and Cr2O3. The morphology and distribution of NiO in oxide scale were affected by oxidation temperature and Ni content. When the Ni content was ≤40at.%, the oxidation resistance of the Cr–Ni alloy coating was enhanced.

Nanostructured TaxC interlayer synthesized via double glow plasma surface alloying process for diamond deposition on cemented carbide

The aim in this work was to improve the adhesion of diamond coating with pre-deposition of a TaxC interlayer on cemented carbide (WC–Co) substrate by double glow plasma surface alloying technique. The following deposition of diamond coating on the interlayer was performed in a microwave plasma chemical vapor deposition (MPCVD) reactor. TaxC interlayer with an inner diffusion layer and an outer deposition layer was composed of Ta2C and TaC nanocrystalline, and it exhibited a special compact surface morphology formed of flower-shaped pits. As the gradual element distributions existed in the diffusion layer, the interlayer displayed a superior adherence to the substrate with significantly enhanced surface microhardness to the original substrate. After CVD process, the preferred orientation of TaC changed from (222) to (200) plane, and a uniform and tense diamond coating with adhesion referred to class HF 2 at least (Verein Deutscher Ingenieure 3198 norm) was obtained on the interlayered substrate. It indicated that the diffusion of Co was effectively inhibited by the formation of TaxC diffusion–deposition interlayer. The TaxC interlayer is most likely to improve the performance of diamond coatings used in cutting tools.

Mechanical and electrochemical properties of Zr and Zr–Er alloyed layers deposited on titanium alloy (TC11)

In this paper, Zr and Zr–Er alloyed layers were deposited onto the TC11 alloy by using double-glow plasma surface alloying technique. Microstructure analysis showed that Zr and Zr–Er alloyed layers were both well bonded to the substrate without defects of porosity and cracks. Nanoindentation test reflected that Zr and Zr–Er alloyed layers not only possessed high hardness but also had good elastic property. The electrochemical behavior of Zr and Zr–Er alloyed layers was comparatively investigated by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 10wt.% HCl solution. The results presented that the changing trend of the sample's corrosion resistance increased in the following sequence: TC11 substrate<Zr alloyed layer<Zr–Er alloyed layer, which indicated that the corrosion resistance of the Zr alloyed layer can be improved by the incorporation of Er.

English

English