Abstract The thermal plasma chemical vapor deposition (TPCVD) is the process which creates thin films with high deposition rate due to high rate chemical reaction caused by introducing reactive gas or alkoxide into thermal plasma jets and is said to be able to create columnar structure thin film according to the reports on these films. In this paper, in order to develop the high deposition rate coating method which can create columnar structure ceramic film in open air, zirconia film deposition by TPCVD is carried out in open air and its structure and component are investigated by using digital microscope and X-ray diffraction. The case of TPCVD conducted in open air, fully crystallized zirconia films could be obtained and yttria stabilized zirconia film also could be obtained by addition of yttrium chloride hexahydride to zirconium oxychloride. The results make it clear that the TPCVD process has great potential for material processing. Paper includes a German-language abstract.

Abstract In this paper, titanium layers with different titanium nitride phases are deposited with variation of the process parameters using the reactive gas plasma spraying process. The layers are characterized with X-Ray Diffraction, light microscopy, Scanning Electron Microscopy, and the Vickers hardness measurement method. Using statistical methods based on Design of Experiments, the influence of the coating parameters on the coating properties is investigated. Quantitative relationships between the nitrogen concentration in the plasma gas, the nitrogen pressure in the spray booth, the substrate temperature during coating, and the layer properties of the nitrogen concentration, hardness, and porosity, are demonstrated. It is observed that the values of all the layer characteristics mentioned increased with an increasing content of nitrogen in the plasma gas or the atmosphere. Paper includes a German-language abstract.

Abstract This paper investigates technologies of wear-resistant coatings and types of cored wire. Novel layers with low porosity and small particle size are produced using the arc spray process. FeCrB + Al and FeCr + Al + C cored wires with steel sheathing and a modified burner are used. The phase composition of the layers and their change due to friction are investigated using the XRD method. Wear tests are carried out with the block-on-ring configuration with different lubrication under a normal pressure of 5 MPa. The results showed good wear resistance of both layer systems. Paper includes a German-language abstract.

Abstract To investigate the accuracy of the sin square Psi method, in this paper, a four-point bending test is developed with which it is possible to load layers with defined tensile stresses. Then, the "effective surface E-modulus," which is calculated from the XRD measurements and the deflection, and the "volume E-modulus," which is calculated from the deflection and the applied load, are presented. High-density stainless steel is applied using HVOF, while the ceramic layers are produced using water-stabilized plasma spraying. The steel layers show a volume of elasticity that is twice as high as that of the surface elasticity module. No surface tension was observed in the ceramic layers during bending. This can be explained by the opening of crack structures as a result of tensile stress. In contrast to this, the pores can be expected to close under pressure loads and thus an increase in the stresses. Paper includes a German-language abstract.

Abstract This article reports on a method for densifying thermally sprayed layers by arc plasma sintering (SPS). Thermal spray ceramic coatings consist from relative high percentage of porosity compared than that of metallic coatings. An investigation of the metallurgical and mechanical properties of flame-sprayed zirconia coatings after SPS at various temperatures and loadings condition was performed. The results obtained in the present work can be summarized as follows: bond strength and microhardness of coating after SPS is increased by three times compared than as-sprayed coating, and X-ray diffraction analysis indicates that the phase of zirconium dioxide-25MgO coating was influenced the physical properties of coating. Paper includes a German-language abstract.

Abstract This paper aims to characterize with innovative methods bond coat and yttria partially stabilized zirconia powder and coating. Bond coat layers realized with different deposition techniques were anlyzed by X-ray Photoelectron Spectroscopy (XPS) in order to compare deposition technologies from the point of view of the oxide presence. X-ray diffraction and Raman microscopy were performed in order to determine the crystallographic composition of Yttria Partially Stabilized Zirconia powders and top coat layers. The surface and interface roughness is expected to affect spallation resistance of the thermally grown aluminum oxide and the life of thermal barrier coating. Raman microscopy allow to map the surface of the examined samples, retrieving the monoclinic zirconia distribution with high spatial resolution. XPS measurements were carried out in order to determine the surface elemental composition. This turns to be useful to measure the amount of oxides which forms during the spraying process and the thermal treatment. Paper includes a German-language abstract.

Abstract In this paper, binary FeAl layers on steel substrates are produced by detonation spraying and examined using a microscope and X-ray diffractometry. Lamellar layers showed the phases FeAl, iron-aluminum alloy, and aluminum oxide. It is observed that with increasing amounts of fuel gas (oxygen and acetylene) and decreasing detonation frequency, the proportion of FeAl in the layers decreases. It is also observed that the microhardness of the layers changed irregularly with reduced proportions of lamellar FeAl phases. Paper includes a German-language abstract.

Abstract This paper investigates the interaction mechanism of ceramic particles and substrate material. Initially, two ceramic powders (pure aluminum oxide and aluminum oxide with 3% by weight of titanium dioxide) are sprayed by detonation spraying and vacuum plasma spraying onto substrates made of stainless steel, on which an electrolytically deposited and subsequently oxidized nickel layer had been applied. The samples are broken after freezing. Then, the interface between layer and substrate as well as the morphologies of the surfaces are examined by means of scanning electron microscopy and X-ray diffractometry. In all samples, regardless of the spraying process, failure is found within the layer and not at the interface, which indicates a high level of adhesion between the ceramic layer and the oxidized nickel substrate. In the case of detonation spraying, the thickness of the layer remaining on the substrate was greater than that of vacuum plasma spraying. Paper includes a German-language abstract.

Abstract This paper uses three types of gases (standard Air, nitrogen, and Ar) as atomization gas, and the arc spraying is carried out in air atmosphere. It examines the microstructure change according to the type of atomization gas and the influence of gas elements on crystalline structure of the titanium coatings by X-ray diffraction and quantitative analysis of nitrogen and oxygen contents in the coatings. The paper aims to research the influence of atomization gas on nitriding and oxidizing process of the titanium. Furthermore, with regard to Ar atomized coating, it investigates the change of crystalline structure with increase of spraying distance in order to research the effect of inert gas, Ar. An influence on the nitrogen content is determined. It turns out that TiN0.3 is formed due to the effect of alpha-titanium as a nitrogen-stabilizing element. Paper includes a German-language abstract.

Abstract This paper compares two methods for determining the composition of Ti/TiN coatings deposited by reactive plasma spraying. The coatings were obtained by spraying titanium powder in a low-pressure N2/Ar atmosphere. The resulting film has a variable nitrogen content in the form of titanium nitrides, depending on gas partial pressure, total pressure, sample-source distance, and other parameters. The composition of the film was determined using X-ray diffraction and X-ray photoelectron spectroscopy. The two techniques provide similar results and either can be used for the compositional characterization of these coatings.

Abstract Aluminum coatings reinforced with either Al 2 O 3 or SiC particles were deposited onto aluminum substrates and subjected to various tests. The coatings were made with mechanically alloyed powders via atmospheric plasma spraying (APS). Both types of coatings had uniformly distributed hard particles, porosities in the range of 4 to 5%, and bond strengths of around 20 MPa. The wear resistance of the SiC-reinforced coatings, however, was almost 35% higher than the coatings containing Al 2 O 3 . X-ray examination (XRD) showed that the Al 2 O 3 particles undergo partial phase transformation during spraying, making them more prone to wear.

Abstract Effects of spray parameters, such as spray distance, SD, and substrate temperature, Ts, and post heat treatment on the structure and properties of plasma-sprayed zircon coatings were investigated. Zircon was totally decomposed by plasma spray; the coatings were composed of tetragonal zirconia (t-ZrO2) and amorphous silica (a-SiO2), because of the rapid cooling of molten particle right after the impingement to the substrate. Porosity of the as-sprayed coatings was highly affected by both of substrate temperature and spray distance. In all range of the spray distance which had been tried in this study, higher substrate temperature resulted in lower porosity of the coatings; the coating with porosity of 2% was obtained at Ts = 1573K with SD = 95mm. Porosity also decreased with decrease of spray distance. By the heat treatment at 1473K, t-ZrO2 transformed to monoclinic zirconia (m-ZrO2) and a-SiO2 crystallized to cristobalite, respectively. Cracks in the coating disappeared, and open porosity decreased. This can be attributed to sintering of SiO2 and phase transformation of ZrO2. After the heat treatment at 1673K, the coating was composed of ZrSiO4 with dispersed fine m-ZrO2 particle. Open porosity of all the coatings increased up to 10% at this temperature. This is because of volume shrinkage during the formation of zircon.

Abstract Titanium carbide cermet spray powder was produced by the SHS process (Self-propagating High-temperature Synthesis) using elemental Ti, C, Mo and prealloyed CrNiMo powders as starting materials. The powder was characterised (particle size distribution, phase structure, morphology) and the internal structure of each cermet particle was found out to be dense consisting of fine distribution of carbides embedded in a metallic matrix. The particle size range suitable for thermal spraying was obtained by sieving and air classifying. The coatings were prepared by HVOF spraying (DJH2600 and DJH2700). The dry abrasion wear resistance was evaluated by the rubber wheel abrasion wear test and electrochemical corrosion behaviour by open circuit potential measurements. According to the XRD analysis the amount of retained carbides in the coatings is high and the carbide phase has a spherical shape also in the coatings. The microstructure of coatings obtained is dense and the coatings possess good properties in wear and corrosion tests. WC-Co-Cr and Cr3C2-NiCr powders were used for comparison.

Abstract Quasicrystals are materials whose structure cannot be understood within classic crystallographic methodology. Quasiperiodic structures have a long-range orientation order but lack transitional periodicity. This non-periodic structure gives quasicrystals a unique range of physical properties including: poor thermal conductivity; excellent crystallographic stability up to their melting point; can be thermally sprayed to display either wear resistant or abradable characteristics; possess excellent release properties (low coefficient of friction); and, they are non-work hardenable. This effort describes parametric conditions utilized to deposit coatings of identical parent metal chemistry but with vastly different end properties.

Abstract Calcined spray-dried hydroxyapatite (Ca10(PO4)(OH)6; i.e., HA) powders were atmospherically plasma sprayed (APS) using various process parameters. The resulting phases within the coating surface and the interface between the coating and the substrate were analyzed using X-ray diffraction (XRD) methods. This XRD revealed the presence of both amorphous (i.e., amorphous calcium phosphate: ACP) and crystalline phases. The crystalline phases included both HA and some impurity phases from the decomposition of HA, such as tricalcium phosphate (α-TCP and β-TCP), tetracalcium phosphate (TTCP) and calcium oxide (CaO). The crystallinity of HA decreased with increasing spray power and stand-off distance (SOD). The percentage of all impurity phases increased with the spray power. The percentage of both TCP and TTCP decreased with the SOD while the CaO percentage increased. In addition, the percentage of ACP and CaO were higher in the interface than at the surface of the coating while the percentage of TCP and TTCP exhibited the opposite effect.

Abstract Tungsten Carbide (WC) thermal spray coatings have had increased acceptance in commercial aircraft applications driven by the desire to replace chromium electroplate due to environmental and economic considerations [1]. In order to confidently replace chromium electroplate by WC thermal spray coatings, evaluation of wear and fatigue characteristics of the WC thermal spray coatings is necessary. For WC thermal spray coatings to replace chromium electroplate in aircraft applications, the coatings must demonstrate wear and fatigue characteristics as good as or better than those of chrome plating. Previous research in this area has shown that the fatigue life of the WC thermal spray coatings can be improved by inducing compressive stresses in the coating. This paper compares the wear characteristics of several types of WC thermal spray coatings with those of chromium electroplate in sliding wear tests following the "block-on-ring" procedures described in ASTM G77 standard. Wear results are interpreted in terms of coating residual stresses and in terms of X-ray diffraction and Scanning Electron Microscope (SEM) analysis.

Abstract FeAl iron-aluminide based materials with the ordered B2 structure are excellent candidates for use in high temperature applications because of the combination of good mechanical properties, low density, low cost and availability of raw materials, and improved oxidation resistance. The aim of this article is to produce an ultra-fine grained FeAl coating by HVOF thermal spraying of milled powders and characterize the fine scale features of its microstructure. Comparison is made with a more conventional coating obtained by projection of powders obtained by atomization. Starting powders and coatings were investigated using X-ray diffraction and transmission electron microscopy. It was observed that the coating obtained from milled powders had a microstructure essentially characterised by a nanometer grain size and the presence of a disordered FeAl phase.

Abstract A reaction-formed NiAl intermetallic compound (IMC) powder has been deposited as a coating onto low carbon steel test coupons by the High Velocity Oxy-Fuel (HVOF) process using both gaseous and liquid fuels. The microstructure of this coating has been examined using scanning electron microscopy and x-ray diffraction and was found to depend on spraying conditions. Oxidation tests on the coating in air, between the temperatures of 800°C-1200°C, revealed that an α-alumina (Al 2 O 3 ) scale formed on the coating's surface. At 1200°C, a nickel spinel (NiO/NiAl 2 O 4 ) and haematite (Fe 2 O 3 ) phases were observed. Diffusion studies were performed to calculate an activation energy for iron ion diffusion in NiAl.

Abstract The present paper describes the synthesis of nanocrystalline 316-stainless steel coatings by high velocity oxy-fuel (HVOF) thermal spraying. The feedstock powders were synthesized by mechanical milling to produce flake-shaped agglomerates with an average grain size of less than 100 nm. The powders were introduced into the HVOF spray to successfully produce nanocrystalline coatings. X-ray diffraction analysis and transmission electron microscopy were used to determine the average grain size of the milled powders. Scanning electron microscopy and transmission electron microscopy were used to study the morphology of the nanometric particles and the microstructure of the as-sprayed coatings. The properties of various coating materials were characterized by microhardness measurements performed on the polished surface of the cross section.

Abstract The corrosion characteristics of two bespoke Ni-Cr-Mo-B alloy powders sprayed by the high velocity oxy-fuel (HVOF) process have been studied using potentiodynamic and potentiostatic corrosion analysis in 0.5M H2SO4. The deposits have also been microstructurally characterised using X-ray diffraction (XRD), scanning electron microscopy (utilising both secondary electron (SE) and backscattered electron (BE) modes), and transmission electron microscopy (TEM). Results from the microstructural examination of the two alloys have revealed a predominantly amorphous/nanocrystalline (fcc) matrix containing submicron boride precipitates as well as regions of martensitically transformed laths. Apparent recrystallisation of the amorphous matrix has also been observed in the form of cellular crystals with an fcc structure. The oxide stringers observed at splat boundaries were found to be columnar grained α-Cr 2 O 3 , though regions of the spinel oxide NiCr 2 O 4 with a globular morphology were also observed. The coatings of the two alloys exhibited comparable resistance to corrosion in 0.5M H 2 SO 4 , as revealed by potentiodynamic tests. They both had rest potentials approximately equal to -300mV(SCE) and passive region current densities of around 1mAcm-2. Microstructural examination of samples tested potentiostatically revealed the prevalence of degradation at splat boundaries, especially those where significant oxidation of the deposit had occurred.