Glow Plasma Surface Metallurgy Technology Research Articles

Impact Wear Behavior of the Valve Cone Surface after Plasma Alloying Treatment

Valves are prone to wear under harsh environments, such as high temperatures and reciprocating impacts, which has become one of the most severe factors reducing the service life of engines. As a lightweight ceramic, CrN is considered an excellent protective material with high-temperature strength and resistance to wear. In this study, a CrN coating was applied onto the valve cone surface via double-layer glow plasma surface metallurgy technology. The formation process, microstructure, phase composition, hardness, and adhesion strength were analyzed in detail. Impact wear tests were conducted on the valve using a bench test device. The SEM and EDS results showed that the CrN coating evolved from an island-like form to a dense, cell-shaped surface structure. The thickness of the coating was approximately 46 μm and could be divided into a deposition layer and a diffusion layer, from the outer to the inner sections. The presence of element gradients within the diffusion layer proved that the coating and substrate were metallurgically bonded. The adhesion strength of the CrN coating measured via scratch method was as high as 72 N. The average Vickers hardness of the valve cone surface increased from 377.1 HV0.5 to 903.1 HV0.5 following the plasma alloying treatment. After 2 million impacts at 12,000 N and 650 °C, adhesive wear emerged as the primary wear mode of the CrN coating, with an average wear depth of 42.93 μm and a wear amount of 23.49 mg. Meanwhile, the valve substrate exhibited a mixed wear mode of adhesive wear and abrasive wear, with an average wear depth of 118.23 μm and a wear amount of 92.66 mg, being 63.7% and 74.6% higher than those of the coating. Thus, the CrN coating showed excellent impact wear resistance, which contributed to the enhancement of the service life of the valve in harsh environments.

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.

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.

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.

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

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.

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.

Double glow plasma chromizing of Ti6Al4V alloys: Impact of working time, substrate–target distance, argon pressure and surface temperature of substrate

Surface chromizing of Ti6Al4V alloys was achieved by double glow plasma surface metallurgy technology. Effects of working time, substrate–target distance, argon pressure and surface temperature of substrate on chromium coating were investigated in detail. The results show that the structure of coating achieved by double glow plasma surface chromizing includes a complete structure of surface deposited layer, inter diffusion layer and sputtering-affected zone. Working time has a significant effect on the composition, morphology and structure of plasma chromium coating. An increasing number of β-Ti turned into α-Ti and TiCr2 phases precipitated in the inter diffusion layer with rising of surface temperature of Ti6Al4V and working time. Argon pressure and the substrate–target distance mainly affected the surface deposited layer of coating. A multilayered deposited structure appeared in the coating when working time was 5 h, which led to the degradation of coating.

The Study about the Effect of Work-Piece Space on Copper-Cerium Alloy Case Thickness and Component

In this paper, the author uses double glow plasma surface metallurgy technology, prepares antibacterial stainless steel with copper-cerium case on its surface, does some research on how work-piece space affects Copper-cerium case thickness and component in the case. According to experiment, we find in the range of 10 mm to 25 mm, copper-cerium case depth firstly increase and then decrease with the distance expands; copper-cerium component first rises and then falls with the work-piece space .When the distance is 15mm, hollow cathode effect forms between two plates, we can obtain ideal copper-cerium alley case.

The Effects of Temperature and Time 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 heat insulation temperature and heat insulation time 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, diffusion layer depth increase with the temperature and time increasing; the deposition layer depth increases with time increasing and decreases with temperature increasing in a certain range.

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.