Double Glow Plasma Surface Research Articles

FRICTION AND WEAR PROPERTIES OF SURFACE PLASMA Cr-W ALLOYING LAYER OFγ-TiAl ALLOY

Cr-W alloying layer was prepared on the TiAl alloy by using the double glow plasma surface alloying technology (DGP). The hardness tests show that the surface micro-hardness of Cr-W alloying layer is greatly increased and the micro-hardness of diffusion layer is 648.8 HV0.1, increased two times more than the matrix. The scratch tests show that the bond between TiAl alloy and Cr-W alloying layer is very good and the layer at least can withstand 70 N vertical load. The friction and wear at room temperature tests show that the friction coefficientof Cr-W alloying layer is about 0.43, that of the matrix is 0.70. The wear scar is narrow, and the depth is small. The wear weight loss and wear rate relative to the matrix decrease greatly. The friction and wear at 500 tests show that the friction coefficient of Cr-W alloying layer is about 0.50, that of the body is 0.75. The wear weight loss and wear rate of Cr-W alloying layer are all less than the matrix.

Wear Resistance of Plasma Surface Copper Infiltrated on 0Cr18Ni9 Stainless Steel

The copper infiltrated stainless steel was formed by double glow plasma surface metallurgy technology on 0Cr18Ni9 steel. A comparative test with untreated samples was carried out. The results indicates that the friction coefficient decreases with the load increasing, and copper infiltrated stainless steel is superior to untreated samples in wear rate and wear resistance, finally makes an analysis of the reasons.

The Effects of Voltage on Cu-Ce Infiltration Layer of 304 Stainless Steel by Double Glow Plasma Surface Metallurgy

The Cu-Ce infiltration layer was formed on 304 Stainless Steel surface by double glow plasma surface metallurgy technology. The effects of source voltage and cathode voltage on surface alloying concentration, surface hardness and infiltration layer depth were analyzed by comparative test. The results showed: In the experimental range, the contents of Cu and Ce, surface hardness, deposition layer depth increase with the source voltage increasing, which is contrary to the cathode voltage; the diffusion layer depth increases with either voltage increasing in a certain range.

Characteristics of Mo–Cr duplex-alloyed layer on Ti6Al4V by double glow plasma surface metallurgy

To improve the wear resistance, a Mo–Cr alloyed layer is prepared on the surface of Ti6Al4V by double glow plasma surface metallurgy. The microstructure and phase constituents of the Mo–Cr alloyed layer are characterized by analyses of SEM and XRD. The results indicate that the alloyed layer is composed of a deposited layer and a diffused layer with thickness of 10μm and 12μm respectively. The modified layer is homogeneous and dense. In the diffused layer the contents of Mo and Cr distributed decreasingly with the depth increasing. Microhardness and nanoindentation tests were carried out to evaluate the mechanical properties of the alloyed layer. The surface hardness reaches 1309HV0.01, and also decreases gradually with the depth increased. The nanoindentation tests show that the alloyed layer has a much smaller displacement and larger elastic modulus than that of the substrate. The tribological behaviors of Mo–Cr duplex-alloyed samples and bare substrate were investigated using a ball-on-disk tribometer under the conditions of lubrication-free at room temperature. Comparing to the substrate, the Mo–Cr alloyed specimen records a lower friction coefficient. The wear mass of Mo–Cr alloyed layer is just 1% of the bare substrate. All the results indicate that the Mo–Cr duplex-alloying has effectively improved the wear resistance of Ti6Al4V.

Enhanced plasma boriding with molybdenum using double glow plasma surface alloying technique

Double glow plasma surface alloying (DG-PSA) has been studied and applied in surface alloying field for more than 20years, in which the alloying elements were always adopted with metal elements, such as Mo, W, Ni and Nb. Recently, this technology has been used for boriding applications through supplying boron with solid boride medium for its no toxic waste. In present paper, boriding and molybdenum alloying were carried out simultaneously by DG-PSA method, which formed a modified layer consisting of an inner Mo–B diffusion layer and an outer Mo–Fe–B composites deposition coating. The results revealed that molybdenizing and boriding hybrid treatment with a special structural source cathode made a remarked increase in deposition rate and the as-formed layers showed a very good adherence due to its metallurgy bonding.

Friction and wear behaviors of Mo–N modified Ti6Al4V alloy in Hanks' solution

A Mo–N surface modified layer on Ti6Al4V alloy was obtained by the double glow plasma surface alloying technique. The structure and composition of the Mo–N modified Ti6Al4V alloy were investigated by X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GDOES). The surface-modified layer contains a Mo–N coating in the subsurface and a diffusion layer between the subsurface and substrate. The X‐ray diffraction analysis reveals that the outmost surface of the Mo–N modified Ti6Al4V alloy is composed of Mo2N. The friction and wear behaviors of the Mo–N modified Ti6Al4V alloy sliding against corundum balls in Hanks' solution were investigated and compared with that of Ti6Al4V alloy. The results show that the Mo–N modified Ti6Al4V alloy has better friction reduction and higher wear resistance properties than that of untreated Ti6Al4V.

Improving corrosion resistance of Q235 steel by Ni-Cr alloyed layer

Ni-Cr alloyed layer was formed on surface of Q235 steel by double glow plasma surface metallurgy to improve the corrosion resistance of substrate. The composition and microstructure of alloyed layer was analyzed by SEM and XRD. Potentiodynamic polarization and electrochemical impedance spectroscopy was applied to evaluate the corrosion resistance of the alloyed layer. The results showed working pressure had a great effect on structure of Ni-Cr alloyed layer, and the dense and smooth alloyed layer was prepared at 50 Pa working pressure. Compared with substrate, Ni-Cr alloyed layer exhibited higher corrosion potential, lower corrosion current density and larger charge transfer resistance, which indicated that Ni-Cr alloyed layer significantly modified the corrosion resistance of Q235 steel.

Effects of Cr-Mo Infiltration Source Cathode Different Mixing Proportion on the Thickness of Alloy Layer

Based on the plasma nitriding technique, the double glow plasma surface metallurgy (DG-PSM) technology was developed. This technology is also known as the Xu-Tec Process which utilizes solid metallic elements such as Ni, Cr, Mo, W, Ti, Al, Nb, Zr and their combinations to accomplish plasma surface alloying. Mo-Cr strengthened coating was prepared on the surface of low carbon steel Q235 by this technology. This coating is used to high wear resistant cold die LD steel. By experiment of the three different prescriptions in source cathode, the effect of source cathode composition on the coating has been studied. The technological parameters were as follows: The ratio of Mo and Cr were 2:1, 4:1 and 6:1. The work-piece material is Q235 low carbon steel. Holding time is 4h. Holding temperature 1050°C.Source cathode structure was threadiness. The consequences of composition analysis and microstructure observation results show that, most approaches the purpose of this research is the ratio of Mo and Cr is 6:1, and the alloyed layer has stronger adhesion with substrate.

Structure-property-performance of nanocomposite Cr–Si–N films synthesized by a duplex surface treatment technique

Abstract

Investigation of W–Mo alloyed layer synthesised by double glow plasma surface metallurgy

In the present study, the W–Mo alloyed layer was deposited on surface of Ti–6Al–4V. Microhardness and nanoindentation testing was used to evaluate mechanical properties of the alloyed layer. The tribological behaviour of W–Mo alloyed layer was estimated using a pin on disc tribometer. The friction coefficient and the wear mass were measured. Results showed that the tungsten and molybdenum content in the alloyed layer decreased gradually from surface to substrate, while the microhardness decreased gradually as the depth increased. The W–Mo alloyed layer had a smaller penetration depth and larger elastic modulus than the substrate. The friction coefficient of the W–Mo alloyed layer was lower than the substrate. The wear mass of W–Mo alloyed layer was one‐third lower than that of the substrate. It can be attributed to the higher hardness of the W–Mo alloyed layer surface which limited plastic deformation of the friction surface and decreased wear mass.

Improvement in Wear and Corrosive Wear Resistance of Ti6Al4V Alloy by Double Glow Plasma Surface Alloying with W-Mo and W-Mo-N

W-Mo and W-Mo-N surface-modified layers on Ti6Al4V alloy were obtained using a double glow plasma surface alloying technique. The morphology, microstructure, and chemical composition distribution of the modified layers were analyzed by scanning electron microscope, Xray diffraction, and glow discharge optical emission spectrometry. The hardness and toughness of the modified layers were measured using a micro-hardness tester, and dynamic repeating press equipment. The wear resistance in ambient air and the corrosive wear resistance in NaCl solution were evaluated using a ball-on-disk wear tester. The results show that W-Mo and W-Mo-N surface modified layers are composed of the alloying layers which vary in composition and phase form along the depth. A microhardness gradient was observed in the modified-surface layers. The surface hardness of the W-Mo-N and W-Mo modified layers was 25.3 and 14.2 GPa, which is seven-fold and 3.9-fold harder than the Ti6Al4V substrate, respectively. W-Mo and W-Mo-N surface-modified layers significantly improved the wear and corrosion resistance of Ti6Al4V. It seems that the wear resistance of W-Mo and W-Mo-N surface-modified layers in NaCl solution is better than that in ambient air owing to the strong lubricating effect of NaCl solution and the excellent corrosion resistance of the modified layers.

P-09 laser ablation performance of double glow discharge sputter deposition Mo on titanium alloy surface

In order to improve the burn-resistant property of titanium (Ti) alloy, Ti-molybdenum (Mo) burn-resistant alloyed layer is coated onto the Ti6Al4V substrate with the double glow plasma surface alloying technology by permeating the Mo. The experiment is performed at a working temperature of 800 ˚C to keep the layer warm for 2.5 h under air pressure of 30 Pa. Mo and Ti6Al4V are used as the source electrode and cathode, respectively. The result of X-ray diffraction shows that the alloy phase of Ti and Mo is formed on the surface of Ti6Al4V substrate. The hardness of the alloyed layer on the surface is more than 800 HK. The friction result further indicates that wear rate can be reduced by three orders of magnitude. Laser ablation experiment is used to characterize the burn-resistant properties of the Ti alloy. The result indicates that the laser burn area of the treated Ti alloy is reduced to 1/12 of the untreated sample. Moreover, the burn-resistant properties improved greatly. Current experimental results clearly show that the laser ablation can be used to characterize the burn-resistant property of the material. OCIS codes: 160.0160, 140.3390, 240.6700, 120.0120. doi: 10.3788/COL201109.S10704.

Cooperative effect of surface alloying and laser texturing on tribological performance of lubricated surfaces

The cooperative effect of laser surface texturing (LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated. A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150 μm and the depth of 30–35 μm distributed circumferentially on the disc surface. The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique. A deep diffusion layer with a thickness of 30 μm and a high hardness of HV900 was formed in this alloy. Tribological experiments of three types of samples (smooth, texturing and texturing + alloying) were conducted with a ring-on-disc tribometer to simulate the face seal. It is found that, in comparison with smooth steel surfaces, the laser texturing samples significantly reduce the friction coefficient. Moreover, the lower wear rate of the sample treated with the two surface techniques is observed.

Effect of different alloyed layers on the high temperature oxidation behavior of newly developed Ti 2AlNb-based alloys

The application of titanium aluminide orthorhombic alloys (O-phase alloys) as potential materials in aircraft and jet engines was limited by their poor oxidation resistance at high temperature. The Ti 2AlNb-based alloys were chromised (Cr), chromium–tungstened (Cr–W) and nickel–chromised (Ni–Cr) by the double glow plasma surface alloying process to improve their high temperature oxidation resistance. The discontinuous oxidative behavior of Cr, Cr–W and Ni–Cr alloyed layers on Ti 2AlNb-based alloy at 1093 K was explored in this study. After exposing at 1093 K, the TiO 2 layer was formed on the bare alloy and accompanied by the occurrence of crack, which promoted oxidation rate. The oxidation behavior of Ti 2AlNb-based alloys was improved by surface alloying due to the formation of protective Al 2O 3 scale or continuous and dense NiCr 2O 4 film. The Ni–Cr alloyed layer presented the best high-temperature oxidation resistance among three alloyed layers.

Tribological Properties of Laser Surface Texturing and Molybdenizing Duplex-Treated Ni-Base Alloy

Laser surface texturing (LST) and surface molybdenizing duplex-treatment was performed on Ni-base alloy in order to improve its wear resistance at high temperature. Surface molybdenizing was performed on the laser surface textured Ni-base alloy by a double glow plasma surface alloying technology. The friction and wear properties of the duplex-treated, the single-treated, and the untreated alloys were tested on a ball-on-disk tribometer by rubbing against an alumina ceramic ball from room temperature to 600°C. The topography of the laser surface textured dimples was measured by a white light interferometer and optical microscope. The dimples are 150-200 μ m in diameter and 45-50 μ m in depth. The distance between the dimples is 500 μ m. The molybdenized layer is approximately 20 μ m in thickness. The elastic modulus of Ni-base alloy is improved by molybdenizing. After texturing and the molybdenizing duplex treatment, the friction coefficient of the Ni-base alloy decreases from 0.38 to 0.26 at room temperature and from 0.42 to 0.34 at 600°C. The wear rate of the duplex-treated alloy is much lower than that of the pristine alloy at 600°C due to the textured dimples storing lubricious oxides.

Microstructure and corrosion resistance of Fe-Al intermetallic coating on 45 steel synthesized by double glow plasma surface alloying technology

A binary Fe-Al alloyed layer was synthesized on 45 steel by means of double glow plasma surface alloying technique. The corrosion-resisting layer prepared is composed of a sedimentary layer and a diffusion layer, with a total thickness of about 180 μm. The aluminum content of the alloyed layer shows gradual change from surface to the inside of substrate. The ideal profile is beneficial to the metallurgical bonding of the surface alloying layer with substrate materials. The microstructure of both layers consists of the Fe-Al intermetallic compound, which is FeAl with B2 structure in the sedimentary layer and Fe 3Al with incompletely ordered DO 3 structure in the diffusion layer. The protective film exhibits high micro-hardness. In comparison with the substrate of 45 steel, the corrosion resistance of the aluminized sample is much higher in 2.0% Na 2S and 0.05 mol/L Na 2SO 4 + 0.5 mol/L NaCl mixed solutions.

Electrochemical Corrosion Behaviors of Ti<sub>2</sub>AlNb with Double Glow Plasma Surface Molybdenized

Ti2AlNb orthorhombic alloy is an attractive high temperature structural material for aero-industries, but insufficient wear-resistance is a major drawback which restricts the actual uses of this alloy in many circumstances. A double glow plasma surface molybdenizing on Ti2AlNb alloy had been carried out to resolve this problem. This paper investigated the electrochemical corrosion behaviors of the alloy after molybdenizing. The polarization curves of specimens in three corrosive media, 5% H2SO4, 5% HCl and 3.5% NaCl, were measured. The eroded surface morphologies were surveyed by SEM. The results indicate that surface molybdenizing decreased the alloy’s corrosion resistance slightly, but still exhibit good performance.

Preparation and Wear Resistance of TiN/Ti Deposition and Diffusion Multi-Layers by Plasma Alloying Process

High quality TiN/Ti multi-layers have been successfully obtained on a carbon steel substrate by double glow plasma surface alloying technique (DGP). The TiN/Ti multi-layers consists of deposition layer and diffusion layer, and then on its surface TiN film (PVD) is deposited to form TiN/TiN/Ti compound multi-layers. In addition, studies were carried to compare TiN/Ti multi-layers, TiN/TiN/Ti compound multi-layers and TiN film (PVD) directly deposited on the surface of the carbon steel and their microhardness and dry friction-abrasion properties were also investigated. The results show that the thickness of TiN/Ti multi-permeated layers is above 10*m; Ti and N concentrations change gradually along the depth of alloying layer. TiN/Ti multi-layers and substrates are metallurgically bonded. Preferred orientation of TiN/Ti multi-layers is crystal surface (200). The hardness of the TiN/Ti multi-permeated layers ranges up 2200HV, its average friction coefficient is lower, abrasion crack is shallower and wear resistance better.

Plasma Surface Alloying Process of a Fe-W-Mo-Co Surface Age Hardening High Speed Steel

The surface age alloy of Fe-Co-W-Mo was formed on 25Cr2Mo2V steel by double glow plasma surface alloying technique. The effects of processing parameters on the depth, composition and constituent phases of surface alloying layer were investigated. Results indicate that the plasma processing parameters influenced significantly the surface alloying process. The composition of the surface layer nears W11Mo7Co23Fe59wt%, the depth of the surface alloying layer is 150μm after processing at 1100°C for 6hr. The microstructure of the cross section was composed of three sub-layers, that is, the deposition layer, the diffusion layer and the matrix. The constituent phases of the deposition layer were Fe7W6 type μ phase Fe2W type laves phase, Fe3Mo and a little amount of M2C type carbide, that of the diffusion layer were α-Fe and some intermetallics.

Cr-Mo Diffusion Layer Made by Double Glow Plasma Surface Metallurgy

Abstract Cr-Mo diffusion layer on carbon steels was prepared by double glow plasma surface metallurgy and treated by ultra-saturated carbonization, quenching and tempering, the excellent wear resistance was obtained. The results indicated that the hardness of surface alloying was up to 1300 Hv 0.025 . The carbides in the alloyed layer were fine and dispersed without coarse eutectic ledeburite. The microstructure of the composite layer indicated that the dimension of surface carbides was less 1μm. The abrasion experimental results showed that the average relative wear resistance of modified-steels was 10.3 times as that of T10 steel by quenching and low tempering. The alloy layer possessed a very strong ability resistance to tempering, and its surface hardness exceeds 595 Hv 0.025 after tempering at 690°C for 4h.