Double Glow Plasma Surface Metallurgy Research Articles

Study on the structure, growth pattern and corrosion behavior of CoCrFeNiAl high entropy alloy coatings - base on hollow cathode effect

The surface of TC18 titanium alloy was coated with a CoCrFeNiAl HEA coating using double-glow plasma surface metallurgy. The structure, phase, and growth mode of the coating were investigated, along with its electrochemical corrosion behavior. The prepared HEA coating, under the influence of the hollow cathode effect and non-equilibrium diffusion, exhibits a composite structure consisting of a deposited layer and an interdiffused layer. It demonstrates robust metallurgical bonding with the substrate, and it exhibits a hardness of 12.66 GPa and an elastic modulus of 158.52 GPa, along with exceptional hardness and high elastic modulus. The primary phase of the coating consists of an FCC solid solution, with a minor presence of Ni3Al and Al8Cr5 phases. TEM results demonstrate that hollow cathode enhanced sputtering effectively refines the grain structure on the substrate surface. The high entropy alloy coating, characterized by a significant abundance of nanocrystalline and amorphous structures, is obtained under the bombardment of high-energy particles. Gradually increasing from the interface to the deposited layer, there is an augmentation in the content of nanocrystals. The transition from the substrate to the sedimentary layer comprises three distinct regions: a surface fine crystal region, a nanocrystalline structure region, and a nanocrystalline and amorphous precipitated phase-rich region. In 3.5 wt% NaCl solution, the electrochemical corrosion rate of the coating is 1.36 × 10−1 μm·year−1, which is about ten times lower than that of the substrate. Moreover, pre-soaking forms a stable oxide film on the coating's surface, effectively preventing corrosion and demonstrating its remarkable corrosion resistance.

A series of plasma innovation technologies by the double glow discharge phenomenon

In order to break the limitation of plasma nitriding technology, which can only be applied to a few non-metallic gaseous elements, the “double glow discharge phenomenon” was defined and then the “double glow plasma surface metallurgy technology” was invented. This double glow plasma surface metallurgy technology can use any element of the Periodic Table for surface alloying of metallic materials. Countless surface alloys with special physical and chemical properties have been produced on the surfaces of conductive materials. By using the double glow discharge phenomenon, a series of new double glow plasma technologies have been developed to apply to surface metallurgy, graphene technology, brazing, sintering, arc plasma surface alloying, nanotechnology, cleaning, carburizing without hydrogen, and so on. This article briefly introduces the basic principles, functions, and characteristics of each technology. The application prospects and development directions of plasma in metallic materials and the machinery manufacturing industry will also be discussed.

Influence of the Electrode Distance on Microstructure and Corrosion Resistance of Ni-Cr Alloyed Layers Deposited by Double Glow Plasma Surface Metallurgy

Influence of the Electrode Distance on Microstructure and Corrosion Resistance of Ni-Cr Alloyed Layers Deposited by Double Glow Plasma Surface Metallurgy

Optimization for solderability of large-size single-crystal diamond with heterogeneity alloys by tantalum coating

To ameliorate the solderability of single-crystal diamond with heterogeneity metals/alloys, tantalum (Ta) coatings were prepared on the diamond by utilizing the double glow plasma surface metallurgy (DGPSM) technique. Using Ag-Cu-Ti solder, the Ta-coated single-crystal diamonds were soldered onto cemented carbide (WC-Co) matrixes. The effects of metallization temperatures on the microstructure, phase, and solderability of the Ta-coated diamond were investigated. The results show that uniform and compact Ta coatings with increased thicknesses are obtained with increasing metallization temperatures. Besides, under all the temperatures, the diffusion layers composed of Ta2C and TaC could be formed at the Ta/diamond interface, which is beneficial to enhance the coating adhesion. The average shear strength of the soldered joint with Ta-coating increases first and then decreases with the increase of temperature. The maximum value is 118.7 MPa on the soldered joint with 850 °C Ta coating, which is approximately 57% higher than without Ta coating. Three failure modes occur during the shear process, including the ductile fracture of the soldered seam, brittle fracture in the interior of Ta carbides at the Ta/diamond interface, and brittle fracture of the single-crystal diamond itself. Among them, the ductile fracture of the soldered seam is the dominant fracture mode.

A modern-day alchemy: Double glow plasma surface metallurgy technology

In the long history of science and technology development, one goal is to diffuse solid alloy elements into the surface of steel materials to form surface alloys with excellent physical and chemical properties. On the basis of plasma nitriding technology, double glow plasma surface metallurgy technology has answered this challenge. This technology, which seems to be a modern-day alchemy, can use any element in the Periodic Table of chemical elements, including solid metal elements and their combinations, to form many types of surface alloyed layers with high hardness, wear resistance, corrosion resistance, and high temperature oxidation resistance on various metal materials. For example, nickel base alloys, stainless steels, and high speed steels are formed on the surfaces of ordinary carbon steels; high hardness, wear resistance, and high temperature oxidation resistance alloys are formed on the surface of the titanium alloy. This article briefly introduces the formation and principle of double glow plasma surface metallurgy technology and summarizes the experimental results and industrial applications. The significance and development prospect of this technology are discussed.

Tribological behaviors of HfC coating prepared on 45 steel via double glow plasma surface metallurgy technique

Purpose45 steel is a common material for the manufacture of various components such as shafts or gears. However, its poor surface properties often limit its applications. The purpose of this paper is to find a way to enhance the surface performance of 45 steel, which is expected to improve the wear resistance of 45 steel.Design/methodology/approachDouble glow plasma surface metallurgy technique was used to prepare hafnium carbide (HfC) coatings on the surface of the 45 steel with two preparation process; one is to diffuse two elements together, while the other is to diffuse step by step. The scanning electronic microscopy and the X-ray diffraction were used to analyze the morphology and phase of the HfC coatings. And then the wear tests were carried out for this coating.FindingsCoating diffused step by step shows better performance; it has a 15-µm alloyed layer which is uniform and dense and its hardness can reach up to 1326.5 Vickers-hardness (HV). While the coating fabricated by diffusing elements together owns a 10-µm alloyed layer and its hardness is 1204.1 HV. According to the wear test results, both coatings have a protective effect on the substrate and the coating prepared by step-by-step diffusion process has less wear volume, indicating that it possesses better friction reduction.Originality/valueA new method which diffuses elements together was successfully used to prepare compound HfC coating, which can reduce the cost of coating preparation and improve the efficiency of coating preparation.

Preparation of NiCr/YSZ two-layered burn-resistant coating on γ-TiAl alloys based on plasma surface metallurgy and ion plating methods

The NiCr/YSZ coating was fabricated on ?-TiAl alloy by double glow plasma surface metallurgy technology and multi-arc ion plating technology. The microstructure, microhardness, bonding strength, and burn resistance of NiCr/YSZ coating were studied in detail. The results showed that the NiCr/YSZ coating was dense and homogeneous, including a duplex structure of top YSZ ceramic coating and underlying Ni-Cr bond coating. The average microhardness of NiCr/YSZ coating was raised by a factor of about 2 compared to the ?-TiAl substrate. The thermal shock test indicated that the composite structure had superior bonding strength and the defects such as metal droplets on the ceramic coating were the source of cracks. The high-energy laser beam destroyed the surface of ?-TiAl alloy, forming protruding combustion products in ablation zone and splashing residues around ablation zone. When coated by NiCr/YSZ coating, the combustion process was delayed through isolating and dissipating heat. The ablation range was controlled and the ablation damage was reduced at the same irradiation power. The NiCr/YSZ coating preliminarily realized to improve the burn resistance of ?- TiAl alloy.

A study on pre-treatment with rotation accelerated shot peening in multi-NbN films by double glow plasma surface metallurgy

Multi-NbN films manufactured by a hybrid process comprising pre-treatment rotation accelerated shot peening (RASP) and double glow plasma surface metallurgy (DG technique) and designed to protect titanium alloys were assessed to determine their tribological and mechanical properties. The surface microstructures of a modified TA15 alloy were characterized using X-ray diffraction, scanning electron microscopy, 3D-profilometer and micro-Vickers hardness testing. The results reveal that the distribution of N concentration on layers was influenced by the pre-treatment with RASP, in which a dense nitride gradient layer was formed inside the films and a new phase β-Nb2N occurred at the film surface. This is because a large number of defects on the surface layer were generated by the pre-treatment with RASP. While multi-NbN films on the original sample without new phase detected can be divided into three zones—NbTi interdiffusion layer, Nb-Ti-N interdiffusion layer, and NbN layer. Strong increase in surface hardness was verified in correspondence of elevated peening velocity, and the hardest RASP-60 m/s sample is up to 30.1803 GPa. However, the thickness of films cannot keep increasing trend in agreement with increasing shot peeing velocity. The thickest films occurred on the RASP-40 m/s sample, is 5.85 μm. The results show that the RASP-treated samples exhibited more serious damage than the untreated sample, due to the formation of β-Nb2N phase with brittle structure which bonding on the course surface are incapable of overcoming the damage of shearing stress from counterparts. And once starting to crack, the films that are supposed to protect the substrate are turned into hard abrasive particles that adversely affect the wear resistance of the substrate.

Double Glow Plasma Surface Metallurgy Technology Fabricated Fe-Al-Cr Coatings with Excellent Corrosion Resistance

Double glow plasma surface metallurgy (DGPSM) technology was applied to obtain a Fe-Al-Cr coating on the surface of Q235 carbon steel. The influence of the sample temperature, gas pressure, the distance between the substrate, and the source electrode on the quality of the obtained Fe-Al-Cr coatings was systematically investigated. The results showed that the parameters for DGPSM have a significant effect on the uniformity, particle size, compactness, and thickness of the coating. Under the optimized parameters (sample temperature: 800 °C, gas pressure: 35 Pa, and electrode distance: 15 mm), the obtained Fe-Al-Cr coating contains Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) solid solution, Cr23C6, and α-Fe(Al), exhibiting excellent corrosion resistance in a 0.5 mol/L H2SO4 solution, which is even better than that of the 304 stainless steel.

A combined experimental and first-principle study on the effect of plasma surface Ta–W co-alloying on the oxidation behavior of γ-TiAl at 900 °C

Abstract

INNOVATIVE METHOD FOR PREPARATION OF Fe–Al–Cr INTERMETALLIC FUNCTIONALLY GRADED MATERIAL ON 1045 STEEL WITH UNIQUE TRIBOLOGICAL PROPERTIES

By combining the plasma ion implantation (PII) technology and double glow plasma surface metallurgy (DGPSM), a Fe–Al–Cr intermetallic functionally graded material was deposited on 1045 steel. The obtained Fe–Al–Cr intermetallic functionally graded material was around 11[Formula: see text][Formula: see text]m in thickness and was composed of a Cr-enriched layer (Cr-enriched Fe–Cr compounds), a Fe–Al–Cr-enriched layer (Fe2AlCr and Al8Cr5 compounds), and a Fe-enriched layer (Fe-enriched Fe–Cr solid solution). The interfacial contact between the Fe–Al–Cr intermetallic functionally graded material and the steel substrate is excellent due to the metallurgical bonding. The wear rate of the Fe–Al–Cr intermetallic functionally graded material was only around 25% of that of the 1045 steel substrate. Due to the different compound distributions in the Cr-enriched layer, Fe–Al–Cr-enriched layer, and Fe-enriched layer, the friction coefficients were different and their tribological behaviors were abrasive wear, oxidative wear and adhesive wear, respectively.

High-Temperature Oxidation of Double-Glow Plasma Tantalum Alloying on γ-TiAl

A Ta-modified layer was prepared on γ-TiAl by double-glow plasma surface metallurgy technique. Based on the results of high-temperature oxidation tests at 700, 800, and 900 °C, we studied the morphology, depth profile, and phase of γ-TiAl and Ta-modified layer by scanning electron microscopy, energy spectrum analysis, and X-ray diffraction analysis. Results showed that the Ta-modified layer was tightly bonded to the substrate without voids and cracks, consisting of the α-Ta outer layer and inner diffusion layer. It was found that the isothermal oxidation kinetic curves of the TiAl with the Ta-modified layer followed the parabolic rate law. Ta element promoted the diffusion of Al and formation of uniformly mixed Al2O3/Ta2O5 films, which prevented the inward diffusion of oxygen and help to the improved high-temperature oxidation resistance.

A New Plasma Surface Alloying to Improve the Wear Resistance of the Metallic Card Clothing

A new surface strengthening process: Plasma surface chromizing was implemented on the metallic card clothing to improve its wear resistance based on double glow plasma surface metallurgy technology. A chromizing coating was prepared in the process, which consisted of a deposited layer and diffusion layer. The surface morphologies, microstructure, phase composition, and hardness were analyzed in detail. The friction behaviors of the metallic card clothing before and after plasma surface alloying were comparatively analyzed under various sliding speeds at room temperature. The results showed that: 1. The chromizing coating on the surface of metallic card clothing was dense and homogeneous without defects, and the metallic card clothing still maintained its integrity and sharpness. 2. The chromizing coating consist of [Fe,Cr], Cr, Cr23C6, and Cr7C3, which contribute to the high hardness. 3. The average microhardness of metallic card clothing increased from 365.4 HV0.05 to 564.9 HV0.05 after plasma surface chromizing. Nano hardness of the chromizing coating was approximately 1.87 times than the metallic card clothing. 4. At various sliding velocities of 2 m/min, 4 m/min, and 6 m/min, the specific wear rates of metallic card clothing were 16.38, 9.06 and 6.26 × 10−4·mm3·N−1·m−1, and the specific wear rates of metallic card clothing after plasma surface chromizing were 2.91, 3.30, and 2.95 × 10−4·mm3·N−1·m−1. Furthermore, the wear mechanism of the chromizing coating gradually changed from adhesive wear to abrasive wear as the sliding velocity increased. The results indicate that the wear resistance of metallic card clothing was improved obviously after plasma surface chromizing.

Microstructure and tribological behavior of W-Mo alloy coating on powder metallurgy gears based on double glow plasma surface alloying technology

In the present paper, plasma surface alloying was implemented on powder metallurgy gears to improve its wear resistance based on double glow plasma surface metallurgy technology. A W-Mo alloy coating was obtained in the process. The morphology, microstructure and phase composition were investigated by SEM, EDS and XRD. The hardness was examined by Vickers hardness test and nanoindentation test. The tribological behavior of powder metallurgy gears before and after plasma surface alloying was evaluated on a ball-on-disc reciprocating sliding tribometer under dry sliding condition at room temperature. The results indicate that the W-Mo alloy coating is homogeneous without defects, which includes deposition layer and interdiffusion layer. The average microhardness of powder metallurgy gears before and after plasma surface alloying is 145.8 HV0.1 and 344.4 HV0.1, respectively; Nano hardness of deposition layer and interdiffusion layer is 5.76 GPa, 14.35 GPa, respectively. The specific wear rate of W-Mo alloy coating is lower than original PM gears. The wear mechanism of W-Mo alloy coating is slight adhesive wear. The W-Mo alloy coating prepared by double glow plasma surface alloying technology can effectively improve wear resistance of powder metallurgy gears.

MECHANICAL PROPERTIES OF THE Fe-Al-Nb COATING BY DOUBLE GLOW PLASMA SURFACE METALLURGY

The Q235 steel was covered by Fe–Al–Nb alloyed coating to improve the mechanical properties of the Q235 steel. This double glow plasma surface metallurgy (DGPSM) surface modification technique was carried out at 1023[Formula: see text]K and pressure of 38[Formula: see text]Pa for 4.5[Formula: see text]h. The surface morphology represented the typical Volmer–Weber mode, an island structure which was accumulated by numerous small particles, and most of the angles formed between three islands were about 120[Formula: see text] where there was no appreciable defect. Meanwhile, in the cross-sectional morphology of the Fe–Al–Nb coating, there was a deposition layer, a diffusion layer and two transition regions between the different adjacent interfaces, and the coating approximate 17[Formula: see text][Formula: see text]m was found to be metallurgically adhered to the Q235 steel. The basic mechanical properties of the Fe–Al–Nb coating and Q235 steel including the hardness, elastic modulus and friction performance were measured and compared. The results showed that the formation of Fe3Al, FeAl, and Fe2Nb intermetallic compounds and Nb carbides in the coating can enhance the mechanical properties of the treated sample. The nanoindentation tests indicated that the hardness and elastic modulus of Fe–Al–Nb coating were 8.08[Formula: see text]GPa and 260.03[Formula: see text]GPa which were much higher than Q235 steel. The sliding friction tests showed that Fe–Al–Nb coating significantly improved the friction performance of Q235 steel at the speed of 300, 600 and 900[Formula: see text]rpm with load 320[Formula: see text]g for 15[Formula: see text]min.

Sliding wear behaviour of Ni-Cr alloying on Ti6Al4V based on double-glow plasma surface metallurgy technology

To improve the wear resistance of Ti6Al4V alloy, Ni-Cr alloy coatings with 40 at.%Ni were prepared on Ti6Al4V alloy surface by double-glow plasma surface metallurgy technique. The friction and wear behaviour of the coatings sliding against Si3N4 at room temperature and 500 °C were comparatively studied. The results show that the alloy coatings comprise a deposited layer, a diffusion-modified layer and a heat-affected zone. The deformed deposition layer plays an anti-friction effect as a soft film. The tribological behaviour of diffusion layer is abrasive wear. Ni-Cr surface alloying process significantly reduces the friction coefficient of Ti6Al4V alloy and improves the wear resistance properties of Ti6Al4V alloy.

Double glow plasma surface Cr-Ni alloying of Ti6Al4V alloys: Mechanical properties and impact of preparing process on the substrate

Surface Cr-Ni alloying of Ti6Al4V alloys was achieved by double-glow plasma surface metallurgy technology. The adhesion strength and nano-indentation hardness of Ti-CrNi alloy coatings with 20, 40, 60, and 80 at% Ni contents were investigated respectively. Effects of process on the metallographic structure, tensile strength and fatigue resistance of Ti6Al4V alloys were analyzed in detail. The results show that Ti-CrNi alloy coatings were dense, uniform, and compact, including a complete structure of deposited layer, interdiffusion layer, and sputtering-affected zone. With increasing of Ni, the adhesion of the deposited layer raised. However, the nano-hardness of the deposition layer gradually declines. The addition of Ni does not have significant impact on the nano-hardness of interdiffusion layer. Plasma alloying treatment resulted in the α-phase grain size of Ti6Al4V increased and a “net structure” appeared. After plasma alloying, the tensile strength of Ti6Al4V was about 2.1% higher than the solid solution annealing state. However, the fatigue life of Ti6Al4V after plasma alloying process declined.

Microstructural characterization and tribological behavior of surface plasma Zr-Er alloying on TC11 alloy

The Zr coating and Zr-Er coating are grown on TC11 substrate by double-glow plasma surface metallurgy technique, followed by the wear tests at ambient temperature and 500 °C. The data of nanohardness and elastic modulus of the samples are collected by the nano-indentation test. The adhesion strength of coatings is investigated by means of the scratch test. The study of wear resistance is performed using a ball-on-disc wear test system by running against the Si3N4 ball and measured by scanning electron microscope (SEM) and X-ray diffraction (XRD). Experimental results indicate that the nanohardness of the Zr coating and Zr-Er coating are 5.94 GPa and 7.98 GPa, respectively, which are 1.79 times and 2.41 times greater than that of TC11 substrate. Zr coating and Zr-Er coating realize the metallurgical bonding with TC11 substrate with continuous and compact structure. Compared with the Zr coating and TC11, the Zr-Er coating presents the lowest specific wear rates, which are 1.689 × 10−6 mm3 Nm−1 and 1.851 × 10−6 mm3 Nm−1 at ambient temperature and 500 °C respectively, indicating the excellent and improved wear resistance of TC11.

TRIBOLOGICAL BEHAVIOR OF Al–Cr COATING OBTAINED BY DGPSM AND IIP COMPOSITE TECHNOLOGY

An Al–Cr composite alloyed layer composed of an Al enriched layer, a Cr enriched layer and a transition layer from the surface to the bulk along the cross-section was deposited on a 45# steel substrate by composite technology, where Cr was deposited using double glow plasma surface metallurgy (DGPSM), and Al was then implanted by ion implantation (IIP) to achieve higher micro-hardness and excellent abrasive resistance. The composite alloyed layer is approximately 5[Formula: see text][Formula: see text]m, and as metallurgical adherence to the substrate. The phases are Al8Cr5, Fe2AlCr, Cr[Formula: see text]C6, Cr (Al) and Fe (Cr, Al) solid solution. The wear resistance tests were performed under various rotational speed (i.e. 280, 560 and 840[Formula: see text]r/min) with silicon nitride balls as the counterface material at ambient temperature. The Al–Cr composite alloyed layer exhibits excellent wear resistance when the speed is 280[Formula: see text]r/min with a friction coefficient as low as 0.3, which is attributed to Al8Cr5 in the Al implanted layer that withstands abrasive wear. Better wear resistance (friction coefficient: 0.254) at 560[Formula: see text]r/min is resulted from the formation of a high micro-hardness zone, and an oxidation layer with lubrication capacity. In addition, the composite alloyed layer suffers severe oxidative wear and adhesive wear at 840[Formula: see text]r/min due to the increment of the frictional heating. When compared to the 45# steel substrate, the enhanced wear resistance of the Al–Cr composite alloyed layer demonstrates the viable method developed in this work.

Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel’s wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer’s oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10−4 mm3/N m, which was only 45.2% of the untreated sample.