Microstructural and Tribological Characterization of Duplex Coatings with Additional Ion Bombardment

THE FILM DEPOSITION process exerts a number ofeffects such as crystallographic orientation,morphology,topography,densification of the films.The optimization procedure for coated parts could bemore effective,knowing more about the fundamentalphysical and mechanical properties of a coating,theirinterdependence and their influence on the wearbehavior.The effects on the structure as well asmechanical and tribological properties of the filmswere investigated in detail in the present research.…     

The effect of deep-case oxygen hardening on the tribological behaviour of a-C:H DLC coatings on Ti6Al4V alloy

A new duplex surface treatment combining the boost diffusion oxidation (BDO) treatment with amorphous hydrogenated diamond-like carbon hard coatings (BDO/a-C:H DLC) has been developed. Experiments results demonstrated that the BDO pre-treatment can effectively improve the scratch resistance and load bearing capacity of a-C:H DLC on Ti6Al4V. This is mainly because the hardened case in Ti6Al4V conferred by the BDO treatment can provide adequate mechanical support for the thin hard top carbon coating.     

物理气相沉积Ti/TiN提高冷冲模具寿命研究

对Cr12MoV冷作模具钢表面进行了单一处理(PVD Ti／TiN)和双重处理(低温等离子氮化 PVD Ti／TiN),通过显微硬度、划痕和磨损试验综合分析了这两种不同处理涂层的摩擦学性能。而且,对PVD Ti／TiN涂覆的“控制臂翻边凸模”进行应用试验。研究结果和应用试验表明：较单一处理,双重处理改善了涂层与基体界面的结合,显著提高了Cr12MoV钢的表面承载能力和耐磨性,PVD Ti／TiN涂覆的“控制臂翻边凸模”寿命提高了2倍多。     

离子渗氮对Cr12MoV表面CrNiTiN镀层耐磨性和表面能的影响

在经过离子渗氮(PN)处理的冷作模具钢Cr12MoV基体上,采用闭合场非平衡磁控溅射离子镀法制备CrNiTiN镀层,与未渗氮的试样进行了膜/基结合力、耐磨性和表面能的对比。研究表明,CrNiTiN膜层具有较低的表面能,但是膜层和基体的结合力较差。Cr12MoV钢经离子氮化后,CrNiTiN膜层与氮化层间结合紧密,提高了膜与基体的承载能力;离子氮化处理使膜层的摩擦系数和磨损率明显降低;离子氮化会提高CrNiTiN膜层总表面能,但不会影响表面的抗粘性能。     

Surface engineering with light alloys—Hard coatings, thin films, and plasma nitriding

Light alloys have been attracting increasing attention over the past decade, since they can be used to reduce weight and save energy. For many years, light metals such as titanium and aluminum have also been used to synthesize hard compound coatings such as physically vapor deposited (PVD) TiN, (Ti,Al)N, and chemically vapor deposited (CVD) Al₂O₃. The coatings field is developing rapidly. Combining plasma-aided coating and diffusion processes has led to the development of so-called “duplex treatment,” consisting of plasma nitriding and subsequent hard coating. Another interesting development is TiN coating of aluminum vacuum parts, such as pumps, to reduce degassing and make the cleaning of the surfaces easier. Despite the many advantageous properties of light alloys, their surface properties sometimes cause problems. For example, galling may be a severe problem with titanium parts, and plasma nitriding has been applied successfully to combat it. However, due to adherent oxide scale, plasma nitriding of aluminum has proven to be more difficult. In this paper, we discuss some recent trends in the application of plasma-aided coating, thin film deposition, and diffusion processes, and give practical examples of industrial applications.     

Preparation of a-C:H/a-C:H:Si:O and a-C:H/a-C:H:Si multilayer coatings by PACVD

Carbon based multilayer coatings were prepared by plasma assisted chemical vapor deposition (PACVD) using methane (CH₄) and hexamethyldisiloxane (HMDSO) or methane and tetramethylsilane (TMS) as precursors. These coatings were deposited in a modified plasma nitriding plant operated at relatively high working pressures of 20 Pa. The multilayer design consisted of a-C:H and a-C:H:Si:O or a-C:H and a-C:H:Si single layers, respectively. The number of single layers and the material of the top layer were varied at constant total coating thicknesses. These multilayer coatings were investigated with regard to their morphology and composition as well as indentation hardness, abrasive wear, lubricant free friction and wetting behavior via contact angle measurements. The multilayer coatings exhibited lower wear rates and higher hardness values than a-C:H:Si:O or a-C:H:Si single layers and lower friction coefficients than pure a-C:H coatings under unlubricated test condition. Utilizing duplex processes, combining plasma nitriding pre-treatment and a following coating deposition, the adhesion of the multilayer coatings on high speed and cold working steel substrates could be considerably improved.     

Fatigue behavior of duplex-treated samples coated with Cr(C,N) film

The effect of a Cr(C,N) PVD coating on the fatigue behavior of 42CrMo4 steel grade was investigated both in a quenched and tempered condition and after nitriding treatment. The latter, so-called “duplex process”, combines a nitriding pre-treatment in order to obtain a hard and stiff substrate and a PVD coating in order to reduce the friction coefficient and improve the wear resistance of tools and mechanical components.Prior to fatigue testing, the surface modifications were characterized by means of X-ray diffraction (XRD), residual stress distribution, Vickers nano-hardness measurements and scanning electron microscopy (SEM) analysis.For the quenched and tempered steels, the PVD coating acts as a high compressive residual stressed zone able to increase the fatigue resistance of the coated component. On the contrary, for the duplex-treated samples, a limited increase in the fatigue limit was detected with respect to uncoated nitrided samples. This result was interpreted by means of the residual stress gradient which does not show high differences for nitrided coated and uncoated samples.     

Use of Double Thermochemical Treatment in the Production of Tools from Structural Steels

It is shown that double thermochemical treatment (nitrocarburizing and nitriding) with subsequent heat treatment can be used for the production of cutting tools from alloy structural steels instead of tool steels. A process for treating milling cutters from steel 38Kh2MYuA and blades from steel 0KhN3MA is suggested.     

Surface Treatment of Cr12MoV Steel towards Long-Life Cold-Work Dies

With the rapid development of the automobile industry in China, there is an ever-increasing demand for long-life cold working dies used for punching automobile components. However, the full potential of such advanced surface engineering technologies as PVD coatings and duplex surface treatments in cold work dies has not been realized. In the present study, Crl2MoV steel has been surface engineered by single PVD Ti/TiN coating and duplex treatment combining low temperature plasma nitriding (LTPN) with PVD Ti/TiN coatings. The properties of Ti/TiN coatings in terms of surface morphology, microhardness, load bearing capacity, bonding strength and wear resistance were evaluated by microhardness,scratch and wear tests. The experimental results show that PVD Ti/TiN coatings can significantly enhance the surface load bearing capacity (especially for duplex treatments) and wear resistance of Cr12MoV steel by more than one order of magnitude. This can be mainly attributed to the hard and well-adherent PVD Ti/TiN surface coatings and strong mechanical support of the LTPN sublayer. While two-body abrasive wear prevails for uncoated Crl2MoV, the micropolishing action of the counterface dominates in surface engineered material.     

PVD hard coatings on prenitrided low alloy steel

The combination of traditional surface treatments such as nitriding with modern plasma-enhanced surface technologies reveals the possibility, particularly in the application to low alloy steels, of obtaining mechanical properties comparable with those of high alloy steels. Gas-nitrided samples of the hardened and tempered low alloy steels 30CrMoV9 and 17CrMoV10 were TiN coated by r.f. magnetron sputtering and ion plating. The requirements to obtain a nitrided substrate that can be coated were given special consideration. For this, various surface modifications of the nitrided substrates were realized by bright nitriding, nitriding with a compound layer and additional steps before coating, such as polishing, grinding and sputter cleaning.

The properties of prenitrided coated steels essentially depend on the structure and properties of the outer part of the nitrided case. TiN on bright nitrided and nitrided substrates with the compound layer removed has a better adherence than on compound layers. The decomposition of the iron nitride during the plasma sputter cleaning of compound layers results in a lower surface hardness and lower adherence of TiN. The highest wear resistances in the Timken test were registered on samples where the compound layer had been removed before TiN coating.     

Increasing surface hardness of austenitic stainless steels by pack nitriding process

This paper investigated the possibility of increasing the surface hardness of austenitic stainless steels under very low nitrogen dissociation pressures of metal nitride powders using pack nitriding process. Thin sheet of 304 type of stainless steel of approximately 1 mm in thickness was used as a substrate for the study. Based on the results of thermochemical calculations, Cr₂N powder was selected as a nitrogen source from a series of metal nitride powders considered for the pack nitriding process, which included Si₃N₄, Mn₄N, BN, AlN and TiN. The pack nitriding was carried out in a sealed alumina retort at temperatures of 860 °C and 910 °C for up to 48 h. The surface was then characterised using techniques of SEM, XRD and microhardness testing. It was observed that the process used increased the surface hardness of the steel, but it also induced precipitation of chromium nitrides in the matrix even under the nitrogen dissociation pressures below 50 Pa. It was also observed that, in the nitrided layer, the γ phase of the steel was partially transformed to the α phase under the pack nitriding process conditions studied.     

Influence of Treatment Sequence on Tribological Performance of Duplex Surface-Treated AISI 1045 Steel

The surface of AISI 1045 steel specimens was modified via two duplex surface treatments of(i) titanium diffusion coating followed by plasma nitriding(Ti–PN) and(ii) plasma nitriding followed by titanium diffusion coating(PN–Ti). A comparative study on the microstructure and wear properties of the fabricated TiN coatings was conducted. A scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, X-ray diffractometer(XRD), and pin-on-disk wear test was utilized to evaluate the microstructures, phases, and wear properties of the coatings. XRD patterns of duplex-treated specimens illustrated that the modified layer consisted of nitride and carbo-nitride phases such as TiN and TiC_(0.7)N_(0.3). The results also showed that Ti–PN treatment led to a low friction coefficient and the lowest wear factors, as compared with the PN–Ti treatment. Oxidation and mild fatigue fracture wear were found to be the main wear mechanism of the Ti–PN coating. The wear mechanism in the PN–Ti specimen involved a higher oxidative wear regime followed by plastic deformation wear regimes.     

An Investigation on Low-Temperature Thermochemical Treatments of Austenitic Stainless Steel in Fluidized Bed Furnace

In this study, the feasibility of using an industrial fluidized bed furnace to perform low-temperature thermochemical treatments of austenitic stainless steels has been studied, with the aim to produce expanded austenite layers with combined wear and corrosion resistance, similar to those achievable by plasma and gaseous processes. Several low-temperature thermochemical treatments were studied, including nitriding, carburizing, combined nitriding-carburizing (hybrid treatment), and sequential carburizing and nitriding. The results demonstrate that it is feasible to produce expanded austenite layers on the investigated austenitic stainless steel by the fluidized bed heat treatment technique, thus widening the application window for the novel low-temperature processes. The results also demonstrate that the fluidized bed furnace is the most effective for performing the hybrid treatment, which involves the simultaneous incorporation of nitrogen and carbon together into the surface region of the component in nitrogen- and carbon-containing atmospheres. Such hybrid treatment produces a thicker and harder layer than the other three processes investigated.     

Applications of Cr-Based Metal Nitride Hard Coatings Using Multi-Magnetron Sputtering Sources and Elemental Metal Targets

METAL NITRIDE or carbide coatings on cutting toolsare effective ways of improving tool performance.Thedriving force for high productivity and precision inmetal machining has led to the requirement of acontinual improvement of conventional hard coatings.It is necessary that those attractive properties of hardcoatings could be simultaneously retained.Highhardness resists abrasive wear.High chemical orthermal stability reduces dissolution wear andmaintains physical properties at a high tempe…     

Corrosion and mechanical properties of duplex-treated 301 stainless steel

Plasma nitriding is a widely used technique for increasing the surface hardness of stainless steels, and consequently, for improving their tribological properties. It is also used to create an interface between soft stainless steel substrates and hard coatings to improve adhesion. This paper reports on the mechanical and corrosion properties of AISI301 stainless steel (SS) after a duplex treatment consisting of plasma nitriding followed by deposition of Cr bond coat and CrSiN top layer by magnetron sputtering. Mechanical properties of the deposited films, such as hardness (H) and reduced Young's modulus (E_r), were measured using depth-sensing indentation. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were carried out to evaluate resistance to localized and to general corrosion, respectively. The corrosion behavior has been correlated with the microstructure and composition of the surface layers, determined by complementary characterization techniques, including XRD, SEM, and EDS. The CrSiN layers exhibited an H value of 24 GPa, whereas the nitrided layer was shown to present a gradual increase of H from 5 GPa (in the nitrogen-free SS matrix) to almost 14 GPa at the surface. The electrochemical measurements showed that the nitriding temperature is a critical parameter for defining the corrosion properties of the duplex-treated SS. At a relatively high temperature (723 K), the nitrided layer exhibited poor corrosion resistance due to the precipitation of chromium nitride compounds and the depletion of Cr in the iron matrix. This, in turn, leads to poor corrosion performance of the duplex-treated SS since pores and defects in the CrSiN film were potential sites for pitting. At relatively low nitriding temperature (573 K), the nitrided interface exhibited excellent corrosion resistance due to the formation of a compound-free diffusion layer. This is found to favor passivation of the material at the electrode/electrolyte interface of the duplex-treated SS.     

超级马氏体不锈钢的等离子渗氮和氮碳共渗

超级马氏体不锈钢(SMSSs)是典型的新一代13%Cr马氏体钢,含碳量较低,并含镍和钼,故具有更好的可焊性和低温韧性。研究表明,不锈钢低温等离子渗氮或氮碳共渗可形成硬的表层从而提高耐磨性。本文对SMSS试样分别在400℃、450℃和500℃进行了等离子渗氮和氮碳共渗,并对处理后的SMSS试样分别采用光学显微镜、显微硬度、XRD和干磨损试验进行了表征。X射线衍射分析证明,氮化铬含量随着渗氮和氮碳共渗温度的升高而增加,也显示出铁和铬的碳化物含量随着处理温度的升高而增加。不同温度下处理后的试样均随着处理温度的升高,磨损体积减小、耐磨性提高。对经等离子处理和未处理的试样所观察到的主要磨损机制都是凿削磨损。     

Plasma nitriding and nitrocarburising of a supermartensitic stainless steel

Abstract

Supermartensitic stainless steels (SMSSs) are a new generation of the classic 13%Cr martensitic steels, lower in carbon and with additional alloying of nickel and molybdenum offering better weldabilty and low temperature toughness. Several works have shown that plasma nitriding and nitrocarburising of stainless steels at low temperatures produces a hard surface layer which results in increased wear resistance. In this work, SMSS samples were plasma nitrided and nitrocarburised at 400, 450 and 500°C. The plasma treated SMSS samples were characterised by means of optical microscopy, microhardness, X-ray diffraction and dry wear tests. The thickness of the layers produced increases as temperature is raised, for both plasma nitriding and nitrocarburising. X-ray diffraction demonstrates that the chromium nitride content grows with temperature for nitriding and nitrocarburising, which also showed increasing content of iron and chromium carbides with temperature. After plasma treating, it was found that the wear volume decreases for all temperatures and the wear resistance increased as the treatment temperature was raised. The main wear mechanism observed for both treated and untreated samples was grooving abrasion.     

电子束淬火与渗氮的复合热处理技术

复合热处理,也称作双重或混合技术,提供了具有新的组织／性能关系的基体化合物层,而处理工序是关键。这种技术能达到单项处理工艺或单项工艺的简单叠加所不能达到的性能和性能梯度化学热处理与高能柬表面淬火特别是电子束淬火相结合,使这项技术取得了显著进展。本文在评述热化学与热（表面）处理技术相结合的历程（重大事件）后,介绍了渗氮后进行电子束淬火和电子柬淬火后进行渗氮的原理及其对微观组织与性能的影响,并讨论了典型的工业应用实例、该领域的进一步发展主要是高能束（电子束或激光束）淬火与硬质涂层技术相结合．     

材料的活性屏等离子渗氮

近年来,等离子渗氮技术的迅速发展和在表面工程领域的应用呈现出减缓的趋势,其原因是传统的直流等离子体技术存在一些固有的缺点,例如,炉温难以保持均匀,等离子体不够稳定以及因打弧而引起工件表面损伤等。克服这些不足之处的努力促使了活性屏等离子渗氮(ASPN)技术的发展。本文从技术和环境优势角度证明,ASPN可以应用于低合金钢、工具钢、不锈钢以及能进行传统直流等离子渗氮的其他钢种。此外,ASPN可以处理不适合直流等离子渗氮的非导电材料,如经氧化处理的钢和高分子材料。从长远看,对环境友好且技术先进的等离子渗氮比传统的盐浴和气体渗氮更有优势。活性屏等离子渗氮技术是充分发挥等离子体技术在化学热处理及有关表面工程中应用潜力的新方法。     

Tribology of nitriding layer, TiN coatings and their complex on AISI D2 steel

The sliding wear and impact wear resistances of D2 steel with nitriding layer, PVD titanium nitride coating and their duplex treatment were investigated. The experimental results suggest that the duplex treatment has the best sliding and impact wear resistances under experimental conditions. And the wear resistance of PVD titanium nitride is better than that of nitriding. The impact wear resistance and wear mechanism of all three surface layers remain unchanged under impact load of 0.2 J or 1 J. All samples end with the same symptom of flaking.