Microstructural evolution during friction surfacing of tool steel H13

Coatings of AISI H13 tool steel were made on low carbon steel by friction surfacing. Detailed microstructural studies and microhardness tests were carried out on the coatings. Studies revealed defect-free coatings and sound metallurgical bonding between the coating and the substrate. In addition, mechanical interlocking on a very fine scale was observed to occur between the coating and the substrate. Coatings exhibited martensitic microstructure with fine grain size and with no carbide particles. Coatings in as-deposited condition showed very high hardness (58 HRC) compared to the mechtrode material in annealed condition (20 HRC). Based on these findings, microstructural evolution during friction surfacing of H13 tool steel is discussed. The current work shows that friction surfaced tool steel coatings are suitable for use in as-deposited condition. Further improvements in coating microstructure and properties are possible with appropriate post-surfacing heat treatment.     

Influence of bias voltage and sputter mode on the coating properties of TiAlSiN

Silicon offers promising opportunities to improve the characteristics of thin coatings. By adding silicon to TiAlN, the oxidation resistance as well as the tribological properties can be increased and improved. To analyze the influence of the silicon content on the coating properties of TiAlSiN, it is necessary to keep the ratio of the other coating elements constant by using the right target configuration. Within this study, TiAlSiN coatings were deposited on hot work steel AISI H11 by using magnetron sputtering (Cemecon CC800/9 sinox ML). This steel was previously plasma nitrided to increase the hardness and hence the carrying load of the substrate, avoiding shell egg effect during the analysis. Different sputter modes were used to analyze the possibility to produce TiAlSiN by utilizing a pure low conductive silicon target. The bias voltages were systematically varied to see their influence on the structure and chemical compositions of the coating which were investigated by means of scanning electron microscopy and energy dispersive X‐ray spectroscopy (EDX). Furthermore, the roughness of the surface of the coatings was measured by an optical three‐dimensional surface analyzer. The results of this study serve as a basis for further investigations regarding the variation of the silicon content of TiAlSiN coatings.     

Structure and mechanical properties of PVD coatings deposited onto the X40CrMoV5-1 hot work tool steel substrate

This work presents the research results on the structure and mechanical properties of coatings deposited by PVD methods on the X40CrMoV5-1 hot work tool steel substrates. The tests were carried out on CrAlSiN, CrAlSiN+DLC, CrN and WC/a-C:H coatings. It was found that tested coatings have nanostructural character with fine crystallites, while their average size fitted within the range 3-13 nm, depending on the coating type. The coatings demonstrated a dense cross-sectional morphology as well as good adhesion to the substrate, the latter not only being the effect of interatomic and intermolecular interactions, but also by the transition zone between the coating and the substrate, developed as a result of diffusion that caused mixing of the elements in the interface zone and the compression stresses values. The critical load L_C2 lies within the range 45-55 N, depending on the coating type. The coatings demonstrate a high hardness (4000 HV).     

Untersuchung der Einflüsse von Substratrauheit und Spritzpartikelgröße auf die Haftung thermisch gespritzter Schichten

About the influence of substrate roughness and spray particle size on the adhesion of thermal spray coatings The influence of substrate roughness and spray particle size on the adhesion of thermal spray coatings was researched systematically. In addition to established spray materials (Cr₂O₃, WCCo, NiCr) and spraying processes (atmospheric plasma spraying (APS), high velocity flame spraying (HVOF)) different substrate materials (steel, stainless steel, aluminum) were included in the research work as well.     

SEM study of defects in PVD hard coatings

Hard coating defects are produced by foreign particle contamination on substrate surface before and during coating, or due to arcing. In this work, CrN, TiAlN and CrN/TiAlN multilayer hard coatings were prepared by thermoionic arc ion plating deposition system BAI 730 (Balzers) and by sputter deposition in CC800 (CemeCon). We investigated the concentration of defects, its size and structure after tool steel substrate surface pretreatment (polishing, ion etching) as well as after deposition by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM).     

Synthesis and characterization of functionally graded nickel‐nickel coated ZrO2 composite coating

Electroless‐nickel plated ZrO₂ (NCZ) particles have been used to produce a functionally graded nickel‐electroless‐nickel plated ZrO₂ composite coating. So, electroless‐nickel plated ZrO₂ particles concentration was continuously increased from 0 to an optimum value in the electroplating bath (Watt's bath). The substrate was ST37 steel and the thickness of the coating was approximately 50 μm. Also a uniformly distributed nickel‐electroless‐nickel plated ZrO₂ composite coating has been manufactured as comparison. The composite coatings were characterized by scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. Structure and phase composition were identified by X‐ray diffraction analysis. Microhardness of the coatings was evaluated by employing a Vickers instrument. Three‐point bend test was carried out to compare the adhesion strength of the coatings. Dry sliding wear tests were performed using a pin‐on‐disk wear apparatus. The electrochemical behavior of the coatings was studied by electrochemical impedance spectroscopy. The microhardness measurements showed that, with increasing the co‐electrodeposited electroless‐nickel plated ZrO₂ particle content in the nickel matrix, the microhardness increases from interface towards the surface of the functionally graded composite coating. Bend, wear and electrochemical test results confirmed that the functionally graded composite coating has higher adhesion, wear resistance and corrosion resistance as compared with the uniformly distributed coating. This has been attributed to lower mechanical mismatch between coating and substrate in functionally graded composite coating with respect to the uniformly distributed one.     

Structure, mechanical properties and corrosion resistance of nanocomposite coatings deposited by PVD technology onto the X6CrNiMoTi17-12-2 and X40CrMoV5-1 steel substrates

This article presents the research results on the structure and mechanical properties of nanocomposite coatings deposited by PVD methods on the X6CrNiMoTi17-12-2 austenitic steel and X40CrMoV5-1 hot work tool steel substrates. The tests were carried out on TiAlSiN, CrAlSiN and AlTiCrN coatings. It was found that the structure of the PVD coatings consisted of fine crystallites, while their average size fitted within the range 11–25 nm, depending on the coating type. The coatings demonstrated columnar structure and dense cross-sectional morphology as well as good adhesion to the substrate, the latter not only being the effect of adhesion but also by the transition zone between the coating and the substrate, developed as a result of diffusion and high-energy ion action that caused mixing of the elements in the interface zone. The critical load L _C2 lies within the range 27–54 N, depending on the coating and substrate type. The coatings demonstrate a high hardness (~40 GPa) and corrosion resistance.     

Effect of particle size on the electrochemical corrosion behavior of X70 pipeline steel

In this study, by using a standard quartz replace of sandy soil particles, the effect of soil particle size (0.1–0.25 mm, 0.6–1.0 mm) on the electrochemical corrosion behavior of X70 pipeline steel in sandy soil corrosive environment simulated by 3.5 wt% sodium chloride (NaCl) was investigated through polarization curve and electrochemical impedance spectroscopy (EIS) technology. The results indicated that the polarization resistance of X70 steel decreased with decreasing particle size. For all polarization curves, the right shift of cathodic branch with decreasing particle size, suggesting that the cathode oxygen reduction process is accelerated. The corrosion of X70 steel is controlled by the process of cathode diffusion and oxygen reduction. This can be attributed to the effect of gas/liquid/solid three‐phase boundary (TPB) zone on cathodic process of X70 steel, and the corrosion rate is mainly determined by the cathodic reaction. EIS of X70 steel consisted of two capacitive loops with 7, 60 and 90 days buried corrosion, and the charge transfer resistance of X70 steel increased with increasing particle size.     

HVOF金属陶瓷涂层的冲蚀失效行为研究现状

超音速火焰喷涂具有粒子飞行速度高、涂层质量好、沉积速度快、材料选择性好以及与基体的结合强度高等优点。冲蚀是水轮机过流部件、轮船螺旋浆、泥浆泵及钻杆等的主要失效形式之一。HVOF技术制备的金属陶瓷涂层因其能显著提高金属零部件的耐冲蚀性能而受到广泛应用。本文对国内外HVOF喷涂金属陶瓷涂层的冲蚀失效行为进行综述,系统归纳了冲蚀颗粒粒径、冲蚀速度、攻角等外部因素及涂层的结合强度、孔隙率、涂层颗粒尺寸、碳化物颗粒的大小等内部因素对HVOF喷涂金属陶瓷涂层冲蚀失效行为的影响机制。并指出综合评价外部服役条件和自身性能参数对涂层冲蚀失效行为的作用机理是本领域今后研究的重点方向之一。     

PVD‐CrN Beschichtungen auf Magnesium AZ91hp und Stahl 100Cr6 – Untersuchung des Substrateinflusses auf die Schichteigenschaften

PVD‐CrN coated magnesium alloy AZ91hp and steel 100Cr6 – Investigation on the influence of the substrate material on coating properties PVD‐chromium‐nitride coated samples of substrates of the magnesium alloy AZ91hp and the roller and ball bearing steel 100Cr6 were investigated regarding structure, mechanical characteristics, adhesion and internal stresses. For the coatings the parameters layer thickness and substrate BIAS voltage were varied. Both substrate materials were coated in one lad. Results of the x‐ray analysis of the internal stresses show significant differences between the coated magnesium and the coated steel substrates. In the case of the variation of the substrate BIAS voltage, for the coated steel a dependency of the internal stresses to coating parameters could be obtained. For the coated magnesium no dependency was recognizable. The coating structure was examined with scanning electron microscopy. Element depth profiles of the coated samples were performed with SIMS.     

Influence of deep cryogenic treatment of high speed steel substrate on TiAlN coating properties

Deep cryogenic treatment in combination with classic heat treatment shows a significant improvement in wear resistance of high speed steel tools. The aim of this research was to investigate how the microstructure of the substrate tool steel material, which was altered by deep cryogenic treatment and plasma nitriding, influences the properties of TiAlN coating. The microstructure, topography and composition of the TiAlN coating were investigated using field‐emission scanning electron microscope, atomic force microscopy, XRD, and glow discharge optical emission spectroscopy. The coating adhesion was measured using the scratch test. The sliding wear resistance and the force required to break the coating were determined with the ball‐on‐flat method. Resistance to microabrasion was measured by free ball abrasion test. The results show that deep cryogenic treatment combined with plasma nitriding influence the adhesion of the TiAlN coating to the high speed steel substrate. Wear resistance tests show better wear resistance of deep cryogenic treated samples in comparison with conventionally heat treated ones.     

Surface coverage characterization of tinplates after post‐treatment processes

In this paper, post‐treatments, including reflowing treatment, passivation treatment, and ultrasonic treatment for tinplates with different coating mass, are discussed, and surface characteristics brought by the post‐treatments have also been investigated by grazing incidence X‐ray diffraction and X‐ray photoelectron spectroscopy. Grazing incidence X‐ray diffraction results show the amount of highest iron and FeSn₂ and lowest tin on tinplate with a coating mass of 1.1 g ? m^?2, indicating the poor surface coverage of steel substrate. The amount of lowest iron and tin‐iron alloy and highest tin on tinplate with a coating mass of 11.2 g ? m^?2 indicates the best surface coverage of tinplate among the four test samples. X‐ray photoelectron spectroscopy depth analysis shows that the sample with coating mass of 1.1 g ? m^?2 has a higher amount of iron atomic concentration, which decreases sharply as the coating mass increases, indicating the poor surface coverage by lower coating mass.     

CHEMICAL VAPOR DEPOSITION OF CHROMIUM OXIDE (Cr2O3) COATINGS ON METAL SUBSTRATES FROM CHROMIUM ACETYLACETONE (C5H7O2) 3 - Cr

A chromium oxide (Cr₂O₃) coating was obtained on metal substrates (steel, alloy steel, etc.) by thermal decomposition of chromium acetylacetone (AA-Cr) in oxygen. The nature and quality of these coatings were investigated by a variety of analysis techniques: X ray Diffraction, Raman Spectrometry, Glow Discharge Spectrometry, Scanning Electron Microscopy and Optical Microscopy. Analysis of the influence of the substrate and precursor temperature, of the flowrate of the carrier gas (Ar) and of the reagent (O₂) led to determination of the optimum coating conditions.     

Untersuchung des tribologisch‐mechanischen Verhaltens amorpher Kohlenstoffschichten mittels Load Scanner

Amorphous carbon coatings have a beneficial tribological behaviour since they provide low friction even under dry sliding conditions and at the same time they offer a good wear protection. Under high loads, the applicability of state‐of‐the‐art amorphous carbon coatings is limited by mechanical failure. However, there is still little knowledge concerning the precise failure mechanisms under application‐oriented conditions. In the present study, cylindrical specimens of a cold work tool steel were coated with two commercial amorphous carbon coating systems: a WCC coating with an a‐C:H:W top layer and a DLC coating which architecture is based on that of the WCC coating, but contains an additional a‐C:H top layer. The coated specimens were tested on a load‐scanning test rig in dry sliding contact against uncoated specimens of the same steel substrate. In the tests, the specimens were loaded with a normal force in the range of 13 and 350 N, corresponding to a maximum contact pressure of 1 to 3 GPa. The number of load cycles was varied between 1 and 60. Firstly, the load‐dependent friction behaviour was monitored. Secondly, the tests were stopped at different total cycle numbers allowing for an evaluation of the progress of wear and damage by scanning electron microscopy. For both coating systems, adhesive pick‐up of counter body steel was observed prior to mechanical failure. Whilst the WCC coating system showed first indications of local failure after several load cycles and at contact pressures exceeding 2 GPa, the DLC coating system showed catastrophic failure on a global scale only after few load cycles and over the whole investigated load range.     

Artificial neural network-based prediction technique for coating thickness in Fe-Al coatings fabricated by mechanical milling

The objective of this study was to evaluate the effect of milling time, milling speed and particle size of initial powders on the coating thickness of Fe-Al intermetallic coating by using artificial neural network (ANN). Coating morphology and cross-section microstructures were evaluated using a scanning electron microscope (SEM). It was found that an increase in the milling time provided an increase in the coating-layer thickness due to the cold welding process between particles and the steel substrate. The microstructure of the coating surface was refined by ball impacts in the milling process. As a result of this study, the ANN was found to be successful for predicting the coating thickness of Fe-Al intermetallic coatings. The correlation between the predicted values and the experimental data of the feed-forward back-propagation ANN was quite adequate. The mean absolute percentage error (MAPE) for the predicted values didn’t exceed 7.46%. The ANN model can be used for predicting the coating thickness of Fe-Al intermetallic coating produced for different milling time, milling speed and particle size.     

Corrosion behavior of Al_(0.4)CoCu_(0.6)NiSi_(0.2)Ti_(0.25) high-entropy alloy coating via 3D printing laser cladding in a sulphur environment

High-entropy alloys(HEAs) are of great interest in materials science and engineering communities owing to their unique phase structure.HEAs are constructed with five or more principal alloying elements in equimolar or near-equimolar ratios.Therefore,they can derive their performance from multiple principal elements ratherthan a single element.In this work,three-dimensional printing laser cladding was applied to produce an Al_0.4CoCu_0.6NiSi_0.2Ti_0.25 HEA coating.The experimental results confirmed that the laser cladding could be used to produce a thin coating of 120 μm in thickness.In the high-temperature laser cladding process,some Fe elements diffused from the substrate to the coating,forming a combination of face-centred cubic and body-centred cubic phase structures.The HEA coating metallurgically bonded well with the substrate.Owing to the increased dislocation density and number of grain boundaries,the HEA coating was harder and had a stronger hydrophobicity than X70 steel.The electrochemistry results showed that the HEA coating had better corrosion resistance than X70 steel.Aluminium oxides formed on the surface of the HEA coating had a certain protective effect.However,because of the laser cladding,the HEA coating generated cracks.In future work,the laser cladding technology will be improved and heat treatment will be implemented to prevent formation of cracks.     

Electroless Ni‐P coating on Cu substrate with strike nickel activation and its corrosion resistance

Electroless Ni‐P coating was successfully deposited on Cu substrate by strike nickel activation process. The specific pretreatment steps were discussed. The surface and cross‐section morphologies, phosphorus content, adhesive force, and corrosion resistance were characterized for electroless Ni‐P coating. Scanning electron microscopy shows the compact surface. Energy dispersed X‐ray shows the 11.4% phosphorus content. Adhesive test shows the qualified adhesion of electroless Ni‐P coating to substrate. Porosity test shows pores free of the coating, and immersion test in 10% HCl solution indicates the better corrosion resistance of electroless Ni‐P coating in protecting Cu substrate from the corrosion of Cl ions. Thus, strike nickel activation pretreatment is suitable for electroless Ni‐P coating on Cu substrate.     

Corrosion behaviour of TiN films obtained by plasma-assisted chemical vapour deposition

Titanium nitride (TiN) coatings with a dense structure were prepared on high-speed steel by plasma-assisted chemical vapour deposition (PACVD). The electrochemical polarization measurement of TiN coating was compared with that of the uncoated substrate. It was found that the TiN coating had a higher corrosion potential, and a lower corrosion rate (current density), about three orders of magnitude less than for the steel substrate. The major corrosion mechanism of TiN was pitting corrosion through surface defects and/or open pores. The number and size of pits decreased with the chlorine content of the film. The TiN coating deposited by PACVD, regardless of the amount of residual chlorine, proved to be a good anti-corrosion coating on a steel substrate.     

等离子熔覆铁基涂层的组织及冲蚀磨损研究

采用等离子熔覆法制备了铁基涂层.研究了涂层的组织结构,测试了涂层的显微硬度及耐冲蚀磨损性能,并利用扫描电镜对涂层显微组织、冲蚀表面形貌进行了分析.结果表明:涂层显微硬度是基体材料不锈钢1Cr18Ni9Ti的2倍,最高达到550,涂层冲蚀后质量损失是不锈钢对比试样1Cr18Ni9Ti和0Cr13Ni5Mo的1/2左右.     

Microstructure and mechanical properties of CrAlN coatings deposited by modified ion beam enhanced magnetron sputtering on AISI H13 steel

CrAlN coatings were deposited on silicon and AISI H13 steel substrates using a modified ion beam enhanced magnetron sputtering system. At the modified ion beam bombardment, the effects of bias voltage and Al/(Cr + Al) ratio on microstructure and mechanical properties of the coatings were studied. The X-ray diffraction data showed that all CrAlN coatings were crystallized in the cubic NaCl B1 structure, showing the (111), (200), and (220) preferential orientation. It is noted that the (111) diffraction peak intensity decreased and the peaks broadened as the bias voltage increased at the same ratio of Al/Cr targets power, which is attributed to the variation in the grain size and microstrain. The microstructure observation of the coatings by field emission scanning electron microscopy cross-section morphology shows that the columnar grain became more compact and dense with increasing substrate bias voltage and Al concentration. At a substrate bias voltage of −120 V and a Al/(Cr + Al) ratio of 40%, the coating had the highest hardness (33.8 GPa) and excellent adhesion to the substrate.