There are constantly increasing requirements concerning light-weight concepts in automotive design due to energy saving demands. Additionally reduction of component weight is desired for demountable parts to permit easier handling. One innovative development example in this field is a draw bar consisting of precipitation hardened aluminum featuring significant weight reduction compared to presently applied steel draw bars. However, low wear resistance of aluminum alloys makes sophisticated addition of wear resistant parts in the area of the positive fit necessary. This leads to increased machining time, further costs for purchasing and machining of adapted additional components and further assembling steps. A study on the capability of thermal spray coating deposition in the positive fit area for substitution of the sophisticated wear protection system is carried out. Different HVOF coating systems with variable thicknesses are tested concerning their capability to withstand bending stress. The optimum combination of Ni20Cr bond coats and Cr 3 C 2 - 25 Ni20Cr top coats is applied for prototype production. The prototypes are tested concerning their performance under dynamical load and in corrosion tests. All produced prototypes pass both mechanical and corrosion tests. Prototypes, on which arc-sprayed Ni20Cr coatings are deposited as a low-cost solution, are still in tests.

High Velocity Oxygen Fuel (HVOF) spraying established itself as an effective method in addition to the conventional thermal spray processes within a very short period. Self fluxing nickel alloys, cermets (e.g. WC-Co / Cr3C2-NiCr) as well as oxide ceramic coatings have proved themselves suitable for wear protection applications. Weight reduction, the care of resources and the increase of efficiency for structural components leads to the substitution of customary hard particles. Titanium carbide (TiC) characterizes itself on account of the material features such as the high hardness, the high melting point, the high strength and the low density for the substitution of conventional carbides. The Self Propagating High Temperature Synthesis (SHS) is a suitable process for the production of composite powders. The powders produced by SHS show a high carbide content, which is finely distributed with an almost stoichiometric composition of the TiC inside the powder particles. The carbides are protected against dissociation and oxidation during the thermal spray process by a complete velum of matrix alloy. The current investigations deal with the wear resistance of TiC-composite coatings produced by HVOF compared to conventional wear resistant coatings. The investigations contain the analysis of the microstructure by optical and scanning electron microscope (SEM) and the measurement of the microhardness of the deposited coatings. Special attention is drawn to the interface between the hard particles and the matrix alloy. The optimized coatings are tested with different wear tests, such as Taber-Abraser test, sliding and oscillating wear test and are compared with common wear resistant coatings in order to underline the high potential for different wear applications. Moreover an additional corrosion test (salt fog test) is carried out with regard to the corrosion resistance of the different matrix alloys.

Thermal sprayed ceramic coatings play an important role in those industrial applications where exceptional erosion and wear resistance are required. In particular, nickel-chromium based coatings containing chromium carbide particles dispersion are widely used when environment temperature rises up to 800°C. Thick Cr 3 C 2 -NiCr coatings were produced with two thermal spray processes: Air Plasma Spray (APS) and High Velocity Oxy-Fuel (HVOF). Two different powders have been selected as starting materials. Their dimensional and morphological properties were assessed to verify their sprayability, both in terms of flowability and deposition efficiency. For both APS and HVOF processes, most deposition parameters were selected, after preliminary spraying tests, on the basis of statistical analysis of results, in terms of coating density, hardness and substrate-coating interface quality. The tribological properties of the coatings were evaluated in order to investigate the influence of the deposition process on the behavior of coatings under wear conditions

Metallic coatings as protection against extraordinary attack of mechanical wear mechanisms such as welded layers or sintered coatings are wordwide standardized. There exists a lot of empirical knowledge, but no exact method is known to foresee the grade of wear in dependance of all important influences in tribological systems. Paper text in German.

Recently much research work has been undertaken worldwide to develop iron base materials which can be used for thermal spraying of anti-wear coatings. Besides economical ideas reasons exist like health- and environmental aspects for the usability of iron base materials instead of Ni- or Co containing carbide coatings. Until now, however, iron base materials showed a worse life time under abrasive wear compared with conventional carbide coatings like WC/ CO or NiCr-CrC. This article presents the research work on new iron base materials for wear protection purposes. Thereby, the focus is set on high carbon containing iron-chromium base alloys which solidify under the formation of primary carbides. The material development included the study of different additional alloying elements. The relation of different chemical compositions and their typical microstructure to the wear behaviour is presented in this paper, too. To follow an integral way for the evaluation of the wear behaviour both powders and cored-wires could be produced. Therefore the wear tests considered coatings produced via HVOF, PTA and arc-spraying.

Iron based materials are classified as being more health and environmentally friendly as well as cost-effective (material and machining costs) compared to typical materials used for wear protection applications (e.g. cermets). The advantage which is seen in using very fine powders (< 15 μm), is their potential to spray relatively thin, dense near-net-shape coatings with comparable smooth surfaces. This can lead to lower coating as well as machining costs. In this work fine Fe-based powders (-15+5 μm) have been used in order to produce wear resistant coatings for applications in the printing industry by means of air plasma spraying (APS). With regard to oxidation problems of such fine Fe-based materials a shroud for the air plasma spraying system has been developed and deployed. The resulting coatings have been analysed with respect to the microstructure, micro hardness, chemical and phase composition as well as surface roughness (as-sprayed). The economical aspects have also been considered.

Thermally sprayed Cr 2 O 3 coatings have been shown to provide excellent protection against wear in many engineering applications. These coatings are traditionally applied using air plasma spray technology; however, suspension high velocity oxy fuel thermal spraying (SHVOF) is a promising method to improve coating properties as this technique enables powder feedstocks too small to be processed by mechanical feeders to be sprayed, allowing the production of coatings with improved density and mechanical properties. Furthermore, the addition of graphene nanoplatelets (GNPs) to the liquid feedstock has been shown to improve the mechanical properties of SHVOF sprayed ceramic coatings. In this study, an aqueous based nanometric Cr 2 O 3 suspension and a Cr 2 O 3 suspension with 1 wt.% GNP, prepared via a proprietary process, were sprayed by a SHVOF thermal spray onto 304 stainless steel substrates. The microstructure of Cr 2 O 3 and Cr 2 O 3 + GNP coatings was analyzed using SEM and XRD alongside microhardness, fracture toughness and porosity investigations. Dry sliding wear performance was investigated using a ball on flat tribometer against an alpha alumina ball at loads of 16, 30 and 47 N. The GNP containing coating exhibited improved mechanical properties, however its response to sliding wear was very similar to the non-GNP coating.

Thermal spraying covers a range of spraying processes in which any metallic, ceramic or polymer-based material can be sprayed onto a substrate to be protected. This flexibility of thermal spraying makes the technology extremely successful in different engineering applications. Protection of the metallic components by hard oxide or ceramic-metallic coatings has proven to be an effective way to reduce wear and corrosion. Polymer coatings are increasing in importance as protection against corrosion and wear for several environmental conditions. Polymeric materials typically exhibit a low shear strength and low elastic modulus that make them viable for use under tribological conditions. Thermally sprayed polymers have the potential both to lower material costs and improve coating performance in drastic environments. In this work, a comparative study is carried out to evaluate the performance of some thermoplastic and hydrocarbon derived polymers deposited onto steel by thermal spray technology. Several tests were performed to evaluate the obtained coatings mainly related to tribological performance.

The application of wear resistant coatings onto the wall of aluminium engine cylinder bores by thermal spray have seen much development over the last 10 years, with regards to both equipment design and also to the material system used. While the technology has been successful in allowing the implementation of aluminium engine blocks into mass production, there is still room for improvement. One area that can be improved is the preparation of the substrate material in order to allow a good adhesion of the thermal spray coating. Grit blasting, a traditional preparation technique, is undesirable for a mass production environment due to the risk of the assembly areas becoming contaminated with grit. Therefore, an alternative method has been sought that can offer a suitable bond strength without introducing potential risks in the manufacture line. In this study, NiAl bond coats were sprayed onto aluminium substrates using the Plasma Transferred Wire Arc (PTWA) coating system developed by Ford Motor Company. A variety of surface preparation techniques, including traditional and some more novel methods, were used and analysed with respect to bond strength, ease of application and cost.

This paper discusses the development of Fe-Cr-C-B powder feedstocks for the production of wear-resistant coatings by HVOF spraying. Chromium content in the powder is in the range of 30 wt% and carbon content is about 5 wt%, yielding a unique powder structure that results in coatings with high and well distributed carbide content. Powder and coating microstructure are examined and the results of wear tests are presented. The extent to which the powders can substitute for conventional carbide coatings is discussed as well.

In the semiconductor industry, plasma etching processes are widely used. Process chamber parts that are located in the plasma etching system are also exposed to the harsh environmental conditions. Thus, parts located close to the process area are typically coated with yttria to increase service life, and thus process performance. However, such yttria coatings are usually porous, and thus can be attacked by fluorine containing plasma. In order to increase the lifetime of the components in the plasma etching system, this research project aimed to improve the protective yttria layer by reducing the porosity of the protective layer. Specifically, a design of experiment was employed in which the porosity was the target value. The main effects of the coating parameters and their interactions including the surface treatment before the coating process were determined. Furthermore, the bonding of the protective coating to the component to be protected, as well as the element distribution and the coating morphology were investigated. The results and their ramifications with respect to the envisaged application will be discussed.

For deposition of protective coatings different coating techniques are available. Usually, detailed evaluation of various deposit types and materials is necessary for selection of the best suited coating for specific application fields and demands. Subject of this work are thermally sprayed functional coatings applied as wear (and corrosion) protective layers. Examination of different optimized thermal spray coatings, i.e. HVOF sprayed WC/Co(Cr) and Cr 3 C 2 /NiCr coatings, conventional flame sprayed and fused self fluxing alloy coatings reinforced by hardmetal and APS sprayed oxide Al 2 O 3 /TiO 2 and Cr 2 O 3 coatings, is done in comparison to thick hard chromium platings. Two abrasive wear tests featuring wear by lose abrasive particles are carried out. These impart dry wear conditions according to ASTM G65 (Rubber Wheel test) and wear by abrasive suspensions according to ASTM G75 (Miller test). The work also contains evaluation of newly developed HVOF torch components permitting increased combustion gas, and therefore also particle, velocities concerning the benefit in terms of coating properties. Exemplary evaluation of the new components influence on velocity and temperature of spray particles is carried out by comparative SprayWatch analyses. Both the influence on the coatings microstructure and the wear performance are studied. Coating microstructure is evaluated qualitatively by optical and scanning electron microscopy and the micro hardness HV0.3 is measured. Worn surfaces are studied by SEM in order to deduce wear mechanisms.

This paper analyses the influence of specific coating parameters such as robot velocity, spray distance and part cooling on the risk of crack formation within Chromium- Carbide / Nickel-Chromium coatings. To understand the effect in more detail, metallographic investigations were conducted. These also provide sufficient data to examine other important coating characteristics such as porosity, mechanical stresses and homogeneity. As an additional analytical method Element Mapping is utilised to show the level of oxidation and its impact on the coating microstructure. The methods X-ray diffraction (XRD) and In-situ coating property (ICP)-Sensor are used to investigate the development of stresses in different coatings. With the information from all these examinations a concept was derived to achieve thick, crack-free wear protective coatings.

In this work, suspension high-velocity oxyfuel spraying (SHVOF) with radial injection is shown to be a suitable technique for depositing graphene nanoplatelet layers on stainless steel substrates. The effect of feedstock injection parameters such as flowrate, injection angle, and position are investigated at different flame powers by means of high-speed imaging. In dry sliding wear tests, graphene layers on stainless steel exhibited a friction coefficient of around 0.1 after 1000 cycles and less than 0.3 after 2000 cycles. Compared to uncoated stainless steel, this is an order of magnitude improvement.

The analytic hierarchy process (AHP) has been widely used as one of decision-making method in economic, social, political and technological field, and for evaluating relative strength of preference quantitatively in decision making process. We think that AHP approach would be useful for analyzing and digitalizing expert’s skills, and for transferring to non-skilled people. In this presentation, we show the AHP approach to analyze a decision to select thermal spraying parameters for achieving high quality wear resistive Al 2 O 3 film by atmospheric plasma spraying (APS). From the result of this study, the process of expert’s subjective thinking could be clear and understood for other person.

The laser-flash method is used to determine the thermal diffusivity of HVOF sprayed WC-Co(Cr) and Cr 3 C 2 -Ni20Cr as well as APS sprayed Cr 2 O 3 and electroplated hard chromium coatings in the temperature range between RT and 600°C. Additionally bond and/or corrosion protective coatings like Ni5Al, Ni20Cr and 316L are characterized taking into account the different manufacturing methods twin wire arc spraying, HVCW and HVOF. With respect to the application example of drying rollers in paper industries the Taber-Abraser wear test is applied to evaluate the wear resistance. Finally the coatings are characterized concerning their corrosion resistance by salt fog test and by exposure to humid SO 2 environment. For WC-CoCr feedstock the effect of carbide size and micro hardness on thermal, wear and corrosion properties are studied. WC-CoCr coatings with maximum micro hardness and fine carbides show the best thermal conductivity. The use of coarse carbide feedstock permits manufacturing of coatings with the highest resistance against dry abrasive wear, but the protective function depends severely on the processing conditions.

Newly developed iron based hard alloy powders with high chromium and vanadium contents are used for coating production by means of HVOF and LPPS. Crack free and dense coatings with fairly homogeneous microstructure are possible for both spraying methods. XRD analyses of sprayed coatings prove phase compositions similar to those of the powder feedstock when using HVOF systems. In contrast LPPS coatings contain a large share of amorphous phase. Microhardness of LPPS and HVOF coatings is about 1,200 HV0.3 and 800 - 950 HV0.3 respectively. The higher microhardness of LPPS coatings is attributed to the presence of the amorphous phase. However, LPPS coatings are brittle and tend to crack under mechanical load. Wear resistance of coatings is determined by means of corundum grinding disk and ASTM G65 wear test. Corrosion behavior is characterized by means of salt fog test and electrochemical measurements. Cermet and stainless steel 316L coatings are used for comparative purposes in the investigations.

HVOF sprayed WC/Co(Cr) and Cr 3 C 2 /Ni20Cr composite coatings have gained high acceptance in many industrial applications for protection of components against wear. The achieved coatings have quite good corrosion resistance for use of chromium containing matrices. Present research in the field of PTA-Surfacing resulted in the development of high chromium and high vanadium containing iron based hard alloys with simultaneous improvement of abrasive wear and corrosion resistance. These properties of the PTA-Surfaced coatings were studied and it was found that the newly developed alloys have nearly same wear resistance and improved corrosion resistance compared to Co-based alloys reinforced with Fused Tungsten Carbides (FTC). One major advantage of high chromium and high vanadium containing iron based coatings is machinability by turning and milling processes. These features make it attractive to be used in thermal spraying. The absence of substrate melting in HVOF-spraying is advantageous, as the coatings preserve the properties of the alloy due to prevention of dilution with substrate material in contrast to PTA-Surfacing. High chromium and high vanadium containing iron based atomized powder was used for HVOF spraying and deposition efficiency was measured. The sprayed coatings were studied metallographically by optical microscopy, SEM, XRD and micro-hardness measurements. Later, abrasive wear and corrosion properties of the coatings are investigated.

The application of thermal sprayed coatings has a broad industrial scope, not only applied where it concerns repairing but also as a preventive means. This article focuses on the applications of ceramics as wear and corrosion protection on hydraulic piston rods. It begins with a concise description of the different forms of wear and their mechanisms with some typical examples of worn surfaces. This is followed by an overview of the available coating techniques for enhancing metal surfaces. Next, the article discusses the principle and applications of thermal sprayed coatings. Then, it presents the scope and protection measures of thermal sprayed coatings to failure mechanism. Further, the article discusses the properties, quality control, and testing criteria of the coatings. It describes the chemical composition and chemical analysis of quality control spray powder. Finally, the article ends with a discussion on the examples of thermal sprayed coatings in OEM applications.

TiN reinforced Ti coatings were produced by using the arc spraying process. TiN hard phases were synthesized during spraying using Ar/N 2 reactive atomizing gas. The spray process was realised in an air atmosphere with a shrouded gun and in a chamber with closed loop Ar/N 2 -gas atmosphere. The content of TiN phases in Ti-coatings was increased by rising the N 2 -amount in atomizing gas during spraying. Sprayed coatings obtained a graded hardness ranging from 450HV 0.1 near the substrate up to 650HV 0.1 near the top (mean values). TiN-particle precipitations exhibited micro hardness up to 1350HV 0.1 . Structure investigations of manufactured coatings proved that they consist of pure titanium, titanium nitrides and small amounts of titanium oxides. Wear resistance of the coatings, tested by Taber Abraser and Pin on Disc, decreases from the coating surface to the substrate. According to Kesternich test, Ti/TiN-arc sprayed coatings exhibit good corrosion resistance.