Wear resistance of plasma coatings on mild steel

Mild steel was coated by different materials using plasma spray technique. Materials used as coatings are Ni-5% Al and WC-17% Co. The thickness of the coatings varied between 0.05 to 1.5 mm. The porosity of different coatings decreased with increase in thickness of the coat. The roughness of coating material decreased after wear testing. Microstrueture study has been conducted for coatings of different materials before and after wear testing. Wear tests have been conducted under different aqueous environments at room temperature. The wear resistance of Ni-5% Al coating was improved by heat treatment. X-ray diffractometry showed the presence of NiO in the outer layer of the Ni-5% Al coating. The thickness of the coating, type of coating, heat treatment conditions, and the environment of testing proved to affect the rate of wear resistance.     

Influence of ion implantation and overlay coatings on various physico-mechanical and wear properties of stainless steel,titanium and aluminium

This work represents the data on the wear behaviour of 304 stainless steel, commercial grade titanium and commercial grade aluminium without and with different surface treatments, namely ion implantation of boron and nitrogen and overlay coatings of titanium carbide and nitride.The surface treatments were characterized by phase identification, hardness, bend strength, as well as adhesion of overlay coatings. Wear properties were evaluated in adhesive, erosive and abrasive modes of wear.The experimental results showed that surface treatments produced measurable changes in hardness and strength. The results of adhesive wear tests indicated that the wear resistance of all the substrate materials can be considerably improved by overlay coating with superhard materials in dry as well as lubricated test conditions. Ion implantation resulted in improvement of wear properties for only a limited regime of adhesive wear under lubricated conditions and for the abrasive mode of wear. Overlay coatings produced a marked improvement in abrasive wear tests under lubricated conditions on all substrate materials.     

电流密度对Ni-W合金镀层摩擦磨损性能的影响

现有的Ni-W合金镀层摩擦磨损性能研究较少涉及镀层制备条件的影响。在不同电流密度下采用脉冲电沉积法在45钢表面制备了Ni-W合金镀层,测试了Ni-W合金镀层在干摩擦及油润滑摩擦条件下的摩擦磨损性能,并观察磨损形貌,分析其磨损机理。结果表明:在干摩擦状态下,随着电流密度增加,Ni-W合金镀层的磨损量逐渐降低,但摩擦系数逐渐升高,45钢的磨损主要是黏着磨损中的擦伤磨损,Ni-W合金镀层主要为磨粒磨损,个别存在少量疲劳磨损;在油润滑摩擦状态下,随着电流密度增加摩擦系数保持稳定,磨损量逐渐降低,Ni-W镀层与45钢的磨损形式均为磨粒磨损,45钢存在少量疲劳磨损。     

Cost-effective way of hard turning with newly developed HSN2-coated tool

EN-31 (AISI 52100, hardness 55 HRC) is one of the difficult-to-cut steel alloys and it is commonly used in shafts and bearings. Nowadays, it is becoming a challenge to the cutting tool material for economical machining of extremely tough and hard steels. In general, CBN and PCBN tools are used for machining hardened steel. However, machining cost using these tools becomes higher due to high tool cost. For this purpose, carbide tool using selective coatings is the best substitute having comparable tool life, while its cost is approximately one-tenth of CBN tool. In this work, the newly developed second-generation TiAlxN super nitride (i.e., HSN²) is selected for PVD coating on carbide tool insert and further characterized using thermogravimetric analysis and differential scanning calorimetry for oxidation and thermal stability at high temperature. Later, HSN²-coated carbide inserts are successfully tested for their sustainability to expected tool life for turning of AISI 52100 steel. In the present study, forces, surface finish, and tool wear are used as a measure to appraise the performance of hard turning process. Experimentally, it is found that speed, feed rate, and depth of cut have considerable impact on forces, insert wear, and surface roughness of the machined surface.     

Abrasive wear of epoxy composites filled by abrasive particles and reinforced by polyamide fibres

Abrasive wear caused by sandy soil of steel coated by epoxy resin was investigated. Experiments were carried out using an abrasive wear tester developed to simulate the wear of the tillage tools under controlled testing conditions. Epoxy coatings were filled by abrasive particles such as aluminium oxide, silicon carbide and silicon oxide of different particle size. Also, epoxy coatings were reinforced by polyamide fibres of different diameters. The test results showed that, relatively lower wear values were displayed by epoxy coatings filled by silicon oxide particles of 5 wt% content. The wear values performed by silicon oxide of (10–20) μm particle size were lower than that displayed by uncoated steel surface. Solid lubricant such as graphite and molybdenum disulphide as filling material caused significant increase in wear due to the weak adhesion between epoxy/solid lubricant layers. Wear of epoxy reinforced by polyamide fibres showed the minimum wear values. Orientation of fibres much affected wear. Parallel fibres represented higher wear than perpendicular ones. The minimum wear was observed for cross plied coatings where shorter wear tracks and higher tensile strength in both perpendicular and parallel directions were existed. The minimum wear values which were lower than that displayed by uncoated steel test specimens were displayed by 0.1 and 0.3 mm polyamide fibre diameters. This observation confirmed the application of the polyamide fibres as reinforcement in epoxy coatings.     

Abrasive wear behaviour of powder flame sprayed coatings on steel substrates

The main purpose of thermal spraying method is to produce wear resistant surfaces. Easy applicability, very low possibility of metallurgical changes and low distortion of coated parts due to low heat transfer to the substrate and salvation of worn parts are some of the practical advantages of this process. In this study, abrasive wear behaviour of powder flame sprayed coatings on steel substrates has been investigated. Coating was carried out onto both hot and cold substrates by using four types of powders. Prior to the wear tests, the coated specimens were machined on a lathe and surface roughness and hardness measurements were carried out on the machined surfaces. Heating the substrates prior to the coating led to the decrease in the hardness of the coating layers. Abrasive wear resistance of flame sprayed coatings was seen to be dependent on the chemical composition and characteristics of coating materials and coating condition.     

Effect of stress on abrasive and erosive wear of steels and sprayed coatings

The effect of stress on abrasive and erosive wear was studied for the hypoeutectoid steel, two hypereutectoid tool steels and flame sprayed coatings. In the experiment, the specially designed tester as well as SEM and contact profilometer were applied. Abrasion and erosion remove asperities protruding from the surface of coatings. The imposed stress increased erosive wear of coatings. Application of compressive stress to steels reduces roughness of the wear scar. Compressive stress caused distinct damage localization in abraded and eroded coatings, mean spacing of surface irregularities Rsm observed in erosion test was about 50% larger than in unstressed coatings. Results of fractal analysis confirm stress-induced change in surface topography.     

Comparing the Effectiveness of Coatings on Carbide andCermet Cutting Tool Inserts

A series of metal cutting experiments was performed on a CNC lathe to evaluate the performance of various coatings on different tool substrates. The workpiece material was plain medium carbon steel and the cutting tool materials were carbide and cermet inserts coated with various single as well as multilayer coatings. Machining was done under various cutting conditions of speed and feed-rate, and for various durations of Cutting. The output parameters studied were the cutting forces (axial, radial and tangential), the surface roughness of the workpiece, as well as the tool wear (crater and flank wear). From these results, the performances of the various cutting inserts are evaluated and compared. Results show that cutting forces are significantly lower when using coated cermets than when using coated carbides although different coatings on the same substrate also result in different cutting forces. However, there is less difference in the surface roughness of the finished workpiece for the various coatings and substrates.     

Wear resistance of KhVG tool steel hardened with composite coatings based on titanium-chromium double carbide

Wear resistance of KhVG tool steel hardened with composite coatings based on titanium-chromium double carbide is studied by means of an automatic wear-measurement system. The influence of deposition methods—electrical discharge alloying and plasma spraying—as well as process variables on the wear resistance of coated steel is discussed. The composition and structure of specimen friction surfaces are examined. The authors of the paper have established the optimal operating conditions for the coatings as well as the most efficient deposition methods for the operation under experimental conditions studied.     

Surface fatigue and wear of PVD coated punches during fine blanking operation

Performance of two different physical vapour deposited (PVD) TiCN and Alcrona® (AlCrN) coatings systems is under investigation. Coatings were deposited on the punches produced from the Böhler S390 Microclean steel. Two different surface preparation techniques were used – wet polishing (high surface roughness) and dry polishing (low surface roughness).Industrial trials of PVD coated punches in fine blanking operation were performed and studied. Wear of punches was analysed in regard to the punch geometry, position in the die and surface roughness, and measured after maximum 100,000 cycles at high loads.Punches with higher surface roughness seem to withstand numerous loading cycles with some traces of coating delamination and wear. On the other hand performance of PVD coatings with smaller surface roughness in a striking way was much worse.Comparative trials of the coatings surface fatigue wear and indentation surface fatigue testing were performed in the laboratory as well. In surface fatigue wear testing coatings were dynamically indented by ball (spherical) indenters made from conventional hardmetal (WC-6 wt.%). Testing parameters were identical to those of industrial trials. The Vickers diamond pyramid indenter was cyclically pressed with 500 N load at single point during indentation surface fatigue testing. Results are in agreement with surface fatigue wear tests results.Finally the microstructural investigations using SEM and XRD techniques were performed for better understanding of the surface fatigue and wear mechanisms during fine blanking process.Results of both trials are in good agreement and allow predicting performance of coatings.     

Properties,applications and manufacture of wear-resistant hard material coatings for tools

Wear processes during machining with cemented carbides and the effect of coatings on wear and on toughness are described. The requirements for coatings relating to optimum tool life are reviewed. Recently developed multilayer coatings with and without ceramic layers are described and examples for improvements in the tool lifetime are given. Additionally, some examples for the application of coatings for milling and chipless forming are presented.The wear-reducing effect of coatings on steel tools is described and possibilities for applications of steel tools coated using chemical vapour deposition (CVD) are elucidated. A number of examples for coated cutting and chipless forming steel tools are described.Finally, useful processes for the coating production are considered. A comparison between physical vapour deposition and CVD processes with respect to the coating temperature, the consistency and the adhesion of the coating is presented. The CVD process for economic production is considered and a suitable coating unit is outlined.     

不同表面处理工艺下H13钢的高温耐磨性能

首先对调质处理状态的H13钢进行了渗氮、物理气相沉积(PVD)镀膜、渗氮+PVD镀膜三种不同的表面处理,然后在UMT-3型摩擦磨损试验机上,对处理后的试样进行600℃的高温摩擦磨损试验,研究了不同工艺下H13钢的高温耐磨性能。结果表明:试样的磨损形式主要是粘着磨损+磨粒磨损,经表面处理后试样的表面硬度大幅度提高,摩擦系数大幅度降低;其中渗氮+PVD镀膜表面处理试样的高温耐磨性能最好。     

Verschleißbeständige Fe‐Basislegierungen mit Niobkarbid

Wear Resistant Fe‐Base Alloys with Niobium Carbide Martensitic Fe‐base alloys from the system Fe‐Cr‐C are widely used as chilled cast irons and tool steels. Because of the low hardness of their FeCr‐carbides this paper reports about new alloys with primarily solidified harder niobium carbides. It focuses on a secondary hardenable welding alloy, a coating material for composite castings, a chilled casting and a corrosion resistant cold work tool steel, which are investigated with respect to their process related microstructure and abrasive wear behaviour.     

Wear monitoring of single point cutting tool using acoustic emission techniques

This paper examines the flank and crater wear characteristics of coated carbide tool inserts during dry turning of steel workpieces. A brief review of tool wear mechanisms is presented together with new evidence showing that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates. Wear also occurs as a result of abrasion, as well as cracking and attrition, with the latter leading to the wearing through the coating on the rake face under low speed conditions. When moderate speeds and feeds are used, the coating remains intact throughout the duration of testing. Wear mechanism maps linking the observed wear mechanisms to machining conditions are presented for the first time. These maps demonstrate clearly that transitions from one dominant wear mechanism to another may be related to variations in measured tool wear rates. Comparisons of the present wear maps with similar maps for uncoated carbide tools show that TiC coatings dramatically expand the range of machining conditions under which acceptable rates of tool wear might be experienced. However, the extent of improvement brought about by the coatings depends strongly on the cutting conditions, with the greatest benefits being seen at higher cutting speeds and feed rates. Among these methods, tool condition monitoring using Acoustic Techniques (AET) is an emerging one. Hence, the present work was carried out to study the stability, applicability and relative sensitivity of AET in tool condition monitoring in turning.     

激光淬火功率对45~#钢抗植物磨料磨损性能的影响

本文以苜蓿草粉为典型植物磨料,系统研究了激光淬火功率对45~#钢抗植物磨料磨损性能的影响。试验结果表明:在实验条件下,材料表面硬度最大值可达679HV,材料硬度最大值在距表面0.2~0.4mm之间;激光淬火后的45~#钢抗植物磨料磨损性能远高于未经激光处理的试件。激光功率对材料硬度和耐磨性的影响趋势并不完全一致,耐磨性最好的试件硬度并非最高;植物磨料对激光淬火后的45~#钢的磨损机理主要为显微切削,与未经激光淬火的试件相比,激光淬火后的45~#钢表面犁削深度明显浅而窄,但当激光功率降至1750W时,塑变疲劳和碳化物剥落明显增加。研究结论可为农业机械金属材料的耐磨性设计提供依据。     

Synthesis and Characterization of Cr-ZrO2 Composite Coating Formed by DC and Pulse Electrodeposition

Chromium–zirconia (Cr-ZrO₂) composite coatings were developed on low-carbon steel substrate by direct current (DC) and pulse electrodeposition (PED) technique with different pulse frequency and duty cycles to enhance mechanical properties of the coating. The phases and morphology of the coating were studied with scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. Surface mechanical properties were analyzed by micro-hardness and ball-on-plate wear study. It was found that pulsing and higher pulse frequencies refine the matrix and increase the ZrO₂ content in the coating. Apart from fine structure and dispersion, crystallographic orientation of Cr matrix also gives its effect on hardness and wear properties. Wear mechanism was found to be mainly abrasive in nature with little adhesive inclination in case of DC deposition.     

真空熔烧钴基合金--碳化钨复合涂层材料的耐磨性能研究

采用真空熔烧法制得钴基合金——碳化钨复合涂层材料,借助扫描电子显微镜、X射线衍射仪、显微硬度计等先进的测试手段对涂层的组织结构和表面形貌进行观察分析。应用盘销式摩擦磨损试验机对不同碳化钨含量的复合涂层材料和淬火态45钢进行了磨损试验。试验结果表明,在相同试验条件下,复合涂层的耐磨性显著高于淬火钢,且其耐磨性随碳化钨含量的增加而提高,淬火钢的耐磨性随着载荷的增加迅速降低,而复合涂层的耐磨性则变化不大。     

Differences in dry sliding wear behavior between HVAF-sprayed amorphous steel and crystalline stainless steel coatings

Dry sliding wear behavior of amorphous steel coating(ASC) and crystalline stainless steel coating(SSC)manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, coefficient of friction(COF) of ASC decreases slightly from 0.78 to 0.69. COF of SSC presents a minor difference under various normal loads but increases with sliding time accompanied by relatively large fluctuation.Such a difference in friction behavior between such two coatings can be understood based upon the roles of shear stress and flash temperature. Wear rate of SSC is much higher than that of ASC, suggesting better wear resistance of ASC. The enhanced wear resistance is correlated with high hardness(H), reduced Young's modulus(E_r), and ratios of H/Erand H~3/E_r~2. Detailed analyses on worn surfaces and sub-surfaces indicate that the wear mechanisms for ASC include delamination, abrasive and oxidation wear, whereas those for SSC are delamination and oxidation.     

Nitridische und oxinitridische HPPMS‐Beschichtungen für den Einsatz in der Kunststoffverarbeitung (Teil 1)

Nitride and oxy‐nitride HPPMS coatings for the application in the plastics processing (Part 1) In plastics processing adhesive and abrasive wear are some of the main damage mechanisms. For the wear protection and in order to increase the tool life time as well as to improve the quality of the plastic products, binary or ternary chrome‐based coatings like CrN and (Cr,Al)N deposited by physical vapor deposition (PVD) are used. As the chemical composition of the coating has a significant impact on the surface oxide layer formed after deposition and therefore on the wetting behavior of the plastic melt on the tool surface, the aim on this work was to synthesize different coatings from the system Cr‐Al‐O‐N. Therefore, a nitride coating (Cr,Al)N and two quaternary oxy‐nitride coatings (Cr,Al)ON were deposited by using a dcMS/HPPMS (direct current magnetron sputtering/high power pulse magnetron sputtering) hybrid process by varying the oxygen flux. This articles emphasis is on explaining the influence of varying the oxygen flux during the coating process on the coating properties as well as the composite properties towards the plastic mould steel. On this basis a follow up article in the next issue will concentrated on the more application oriented system properties of the three coating systems towards a polycarbonate melt.     

Characterization and wear behavior of plasma-sprayed Al2O3 and ZrO25CaO coatings on cast iron substrate

Plasma spraying is one of the methods used for combating wear. Despite of its wide spread industrial use, little is known about the basic friction behavior and mechanism by which such coatings wear. In this work, the abrasive wear resistance of plasma-sprayed ceramic coatings on cast iron substrate has been investigated through pin-on-disc test. It was found that the coefficient of friction and wear affected mainly by splats and porosity, surface roughness, and coating thickness. The coefficient of friction is found to be more significantly affected by load than by other test parameters. This work also includes the characterization of coatings.