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In order to investigate the cavitation erosion (CE) resistance of high-alloyed ferrous hardfacings, the three different deposits were pad welded by the shielded metal arc welding (SMAW) method. Consumable electrodes differed in the content of carbide-forming elements, and pad welds were deposited onto the S235JR structural. The CE tests, conducted according to ASTM G32 standard, indicated that hardfacings reveal lower mass loss than the reference stainless steel AISI 304 (X5CrNi18-10). The hardfacings show increasing resistance to CE in the following order: Cr-C < Cr-C-Mo < Cr-C-Mo-V-W. The reference steel revealed more than twenty times higher material loss in the CE test than Cr-C-Mo-V-W hardfacing, which had outstanding hardness (825HV0.3). The profilometric measurements and scanning electron microscopy investigations showed large changes in valley and peak sizes of the roughness profiles for materials which displayed high erosion rates. The erosion mechanism of the coatings can be classified as brittle-ductile and relies on cracking, chunk removal of material, pits and craters formation, and deformation of fractured material tips and edges. Hardfacing materials failed primarily due to brittle fractures with different severities. Specimen surface degradation follows the changes in Ra, Rz, Rv, and Rp roughness parameters and well-corresponds to the proposed roughness rate (RR) parameter.

The work presents the results of a study on cavitation erosion (CE) resistance of two NiCrSiB self-fluxing powders deposited by oxy-acetylene powder welding on cast iron substrate grade EN-GJL-200. The mean hardness of deposits A-NiCrSiB, C-NiCrSiB is equal to 908 HV, 399 HV and exceeds those of EN-GJL-200 and X5CrNi18-10 reference specimens 197 HV and 209 HV, respectively. To study CE, the vibratory apparatus has been used and tests were conducted according to the ASTM G32 standard. Cavitation eroded surfaces were examined using a profilometer, optical and scanning electron microscopy. The research indicated that the CE resistance, expressed by the cumulative mass loss decreased in the following order C-NiCrSiB > A-NiCrSiB > X5CrNi18-10 > EN-GJL-200. Therefore, hardfacings were characterised by lower cumulative mass loss, in turn, higher CE resistance than the reference sample and therefore they may be applied as layers to increase resistance to cavitation of cast iron machine components. Results indicate that in the case of multiphase materials, hardness cannot be the main indicator for CE damage prediction while it strongly depends on the initial material microstructure. To qualitatively estimate the cavitation erosion damage (CEd) of NiCrSiB self-fluxing alloys at a specific test time, the following factors should be considered: material microstructure, physical and mechanical properties as well as surface morphology and material loss both estimated at specific exposure time. A general formula for the CEd prediction of NiCrSiB deposits was proposed.

The process of conjoined stress cycling and abrasive or erosive wear is encountered in industry. However, very scant attention has been paid till now to this issue. The paper presents two test rigs designed and built to cope with this experimental problem. Tests were carried out on the range of pure iron (Armco), carbon steels namely S235JR, C45, C70U, C80U, C110U and unalloyed cast steels (L40III, L45III and L50III). Tested iron-based alloys differ in chemical composition, microstructure and Brinell hardness ranging from 80HB to 350HB. Stress cycling caused strain hardening of ferrite in hypoeutectoid steels and thus reduced their abrasive wear loss. In the hypereutectoid steel stress cycling impaired integrity of the microstructure thus increasing abrasive wear loss. Alternating stresses enhanced ploughing and cutting micromechanisms of erosion. Tensile stress in the tested cast steel had a stronger effect on wear loss than the prior stress history.

В статті містяться результати випробувань основних типів сталей при терті по нежорстко закріплених частинках абразиву В статье содержаться результаты испытаний основных типов сталей при трении о нежостко закрепленные абразивные частицы The article contains the results of tests of the main types of steels by friction on non-rigidly fixed abrasive particles. The steel presents a wide field of application. The abrasive wear resistance of steel relies mainly on the microstructure, hardness as well as on the abrasive material properties. Moreover, the selection of a abrasion-resistant grade of steel still seems to be a crucial and unsolved problem, especially due to the fact that the actual operating conditions can be affected by the presence of different abrasive materials. The aim of this work was to determine the effect of different abrasive grit materials i.e. garnet, corundum and carborundum on the abrasive wear result of a commonly used in industry practice steels i.e. S235, S355, C45, AISI 304 and Hardox 500. The microstructure of the steel was investigated using light optical microscopy. Moreover, hardness was measured with Vickers hardness tester. Additionally, the size and morphology of the abrasive materials were characterized. The abrasion tests were conducted with the usage of T-07 tribotester (dry sand rubber wheel). The results demonstrate that the hardness and structure of steels and hardness of abrasive grids influenced the wear results. The abrasive wear behavior of steels was dominated by microscratching and microcutting wear mechanisms. The highest mass loss was obtained for garnet, corundum, and carborundum, respectively. The usage of various abrasives results in different abrasion resistance for each tested steel grade. The AISI 304 austenitic stainless steel presents an outstanding abrasive wear resistance while usage of corundum and Hardox 500 while using a garnet as abrasive material. The C45 carbon steel was less resistant than AISI 304 for all three examined abrasives. The lowest resistance to wear in garnet and carborundum was obtained for the S235JR and S355J2 ferritic-perlitic carbon steels and in corundum for Hardox 500 which has tempered martensitic structure.

This manuscript deals with the cavitation erosion resistance of flame-sprayed Al2O3-40%TiO2/NiMoAl cermet coatings (low-velocity oxy-fuel (LVOF)), a new functional application of cermet coatings. The aim of the study was to investigate the cavitation erosion mechanism and determine the effect of feedstock powder ratio (Al2O3-TiO2/NiMoAl) of LVOF-sprayed cermet coatings on their cavitation erosion resistance. As-sprayed coatings were investigated for roughness, porosity, hardness, and Young’s modulus. Microstructural characteristics of the cross section and the surface of as-sprayed coatings were examined by light optical microscopy (LOM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) methods. Coating cavitation tests were conducted in accordance with the ASTM G32 standard using an alternative stationary specimen testing method with usage of reference samples made from steel, copper, and aluminum alloys. Cavitation erosion resistance was measured by weight and volume loss, and normalised cavitation erosion resistance was calculated. Surface eroded due to cavitation was examined in successive time intervals by LOM and SEM-EDS. On the basis of coating properties and cavitation investigations, a phenomenological model of the cavitation erosion of Al2O3-40%TiO2/NiMoAl cermet coatings was elaborated. General relationships between their properties, microstructure, and cavitation wear resistance were established. The Al2O3-40%TiO2/NiMoAl composite coating containing 80% ceramic powder has a higher cavitation erosion resistance than the reference aluminium alloy.

Magnesium and its alloys may be applied as cathodic protection for steel constructions. As the protectors work in water environment, one of the main degradation factors is cavitation erosion. The paper presents results of research on the cavitation erosion of magnesium casting alloy – Elektron 21. The cavitation erosion tests were performed using vibratory apparatus. After the cavitation tests eroded surface and the cross-sections of the specimens were observed by means of scanning electron microscopy. Elektron 21 did not exhibit distinct incubation period of cavitation erosion. The cavitation pits are observed mainly in the α-Mg solid solution grains and on the interfaces between intermetallic phases and the α-Mg. On the other hand, the Mg3(Nd, Gd) eutectic phases are more resistant to cavitation erosion than α-Mg. They are protecting the solid solution from degradation. However, due to their high hardness they undergo cracking and detachment of from the surface. After longer times of cavitation tests, cracks begin to propagate into the material, which leads to crushing of bigger parts of the material.

The researches have concerned cavitation erosion of AlSi7Mg and AlSi11Mg aluminium casting alloys. The alloys have been investigated in the as-cast condition and after the precipitation hardening. The cavitation erosion tests were performed using vibratory cavitation erosion equipment in 5 minutes. Resistance to cavitation of tested materials was estimated by means of MDE (mean depth of erosion) parameter according to ASTM G32. After the cavitation tests eroded surface of the specimens has been observed by means of scanning electron microscopy. The roughness of the surface was measured on profile contact tester. The best resistance for cavitation erosion exhibited AlSi7Mg alloy after heat treatment, the weakest AlSi11Mg alloy in as-cast condition.

The overlay coatings were corrosion tested in a 3% aqueous NaCl solution. The metallic glasses Ni60Nb20Zr20 coating plasma sprayed at 250 A arc current and the 45–50 mm spraying distance revealed the outstanding corrosion resistance and outperformed pad welded coatings. For all sprayed metallic glass coatings, the microhardness increased with the rising arc current. The corrosion resistance of Zr55Cu30Al10Ni5 sprayed deposits depends on their porosity and phase composition. The Ni- and Co-based hardfacings offer high corrosion resistance compared with the Fe-based ones. The corrosion resistance of Fe-based hardfacings is reduced by cracks and inclusions present in the coatings.

In thermal barrier coatings (TBC), failure occurs near or at the interface between the metallic bondcoat and topcoat. On high temperature conditions, an oxide scale which is named thermally grown oxide (TGO) occurs along the bond/topcoat interface. For diminishing the creation of TGO, a dense coating with low residual stress and thermal stress buffer layer was preferable. High hardness ceramic coatings could be obtained by gas tunnel type plasma spraying, and the deposited coating had superior property in comparison with those deposited by conventional type plasma spray method. In this study, the gas tunnel type plasma spraying system was utilized to produce a zirconia/alumina functionally graded thermal barrier coating and discussed its physical and mechanical properties, thermal behavior and high temperature oxidation resistance of the coating are discussed. Consequently, the proposed system exhibited superior mechanical properties and oxidation resistance at the expenses of a slightly lower thermal insulating effect. This interlayer is preferred in order to minimize the detrimental effect of the phase transformation of gamma-Al2O3 to alpha-Al2O3.

The paper presents the results of investigation into the thermal fatigue resistance of thermal barrier coatings (TBC). Two groups of double-layered thermal barrier coatings (TBC) were investigated: plasma sprayed with ZrO 2 -8%Y 2 O 3 , Al 2 O 3 -40%TiO 2 or Al 2 O 3 -40%ZrO 2 top coats and powder flame sprayed with ZrO 2 -30%CaO, Al 2 O 3 -40%TiO 2 and Al 2 O 3 -30%MgO. The extent of TBC deterioration experienced in thermal fatigue test was evaluated in the erosion test and SEM examinations. Flame sprayed coatings were found more prone to damage than plasma sprayed ones. The highest thermal fatigue resistance revealed TBC plasma sprayed with PSZ. Numerical calculation with Abaqus 6.7 finite element code was used to calculate temperature and stress variations in the coating throughout the test. Phase stability of plasma sprayed Al 2 O 3 -40%TiO 2 was evaluated by means of X-ray diffraction method. Thermal growth of oxides at the top coat/bond–coat interface and the decomposition of Al 2 O 3 -40%TiO 2 were found to be important degradation mechanisms leading to the spallation of coatings in the diesel engine and the petrol engine exploitation tests.

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.

In the paper, the erosion and abrasion resistance of PTA, TIG and flame deposited coatings was investigated. Hardness of coatings has almost no effect on erosion resistance and incubation period. Microstructure of coatings has significant effect on erosive wear of coatings. No significant correlation was found between results of abrasive and erosive tests. Statistically significant correlation was found between erosive wear intensities determined in tests carried out at similar angles, the total content of B and C correlates with mass loss in abrasion test and erosive wear intensity at normal incidence. Laboratory tests with model abrasives cannot be used as a guide for material selection in industry.

W pracy przedstawiono wyniki pomiarów odporności na zużycie kawitacyjne powłok na osnowie Ni. Powłoki wykonano metodą napawania płomieniowo-proszkowego. Badania kawitacyjne wykonano na stanowisku wibracyjnym zgodnie z normą ASTM G-32. Określono wpływ mikrostruktury, twardości i mikrotwardości wytworzonych warstw na ich odporność kawitacyjną. Przy użyciu mikroskopii elektronowej dokonano identyfikacji mechanizmu zużywania powłok. Obserwacji dokonano w oznaczonych obszarach na powierzchni powłok w wybranych czasach ekspozycji. Powłoki objęte badaniami mogą być rozważane do regeneracji elementów maszyn i urządzeń podlegających zużyciu kawitacyjnemu. Cavitation erosion resistance of coating flame deposited with nickel base powder Abstract In the work results of cavitation erosion test of nickel based coatings were presented. Coatings were pad welded with the oxy-acetylene powder torch. Cavitation tests were conducted on vibratory test rig according do ASTM G-32 standard. The influence of microstructure, hardness and microhardness on cavitation erosion resistance was investigated. The cavitation erosion mechanism was examined by using SEM microscopy. Observations were conducted in specified areas of coatings in defined times of exposition. Presented coatings could be considered to repair cavitation worn machines elements and appliance.

W pracy przedstawiono wyniki pomiarów odporności na zużycie kawitacyjne powłok NiCrBSi oraz powłoki stellitowej. Powłoki na osnowie niklu wykonano metodą napawania płomieniowo-proszkowego, na osnowie kobaltu metodą TIG. Badania kawitacyjne wykonano na stanowisku wibracyjnym zgodnie z normą ASTM G-32. Na podstawie badań makroskopowych oraz przy użyciu mikroskopii elektronowej dokonano identyfikacji mechanizmu zużywania powłok. Określono cechy i właściwości wytworzonych powłok sprzyjające ich odporności kawitacyjnej. Powłoki na osnowie niklu wykazują wysoką odporność kawitacyjną i mogą być stosowane w celu zwiększania odporności elementów maszyn przepływowych. Improvement of cavitation erosion resistance of metal alloys by pad welding of coatings Abstract In the work results of cavitation erosion test of NiCrB- Si and stellite coatings were presented. Nickel based coatings were pad welded with the oxy-acetylene powder torch, cobalt based with TIG method. Cavitation tests were conducted on vibratory test rig according do ASTM G-32 standard. The cavitation erosion mechanism was examined by using macroscopic and SEM microscopy observation. The influence of the microstructure fea- tures and properties of produced coatings on cavitation erosion resistance was investigated. Presented coatings can be applied to increase erosion resistance of fluid machine elements.

Performance of Fe-, Ni- and Co-based alloys was evaluated in sliding wear and in the impact wear tests to simulate wear of valves and valve inserts in internal combustion engines. From the SEM investigations adhesive wear was confirmed by metal transfer between rubbing surfaces while surface deformation testify to abrasive wear. It was found that oxides formed on the surface prevented direct metal-to-metal contact and reduced the coefficient of friction thereby reducing wear. A comparison of wear resistances of Fe, Ni- and Co-based alloys used as hardfacings were given. It is also shown that Ni–Co alloys with Ni-alloy content between 40.4 and 64.3 have a considerable potential, they reveal above 2 times higher wear resistance than plasma-deposited cobalt alloy.

In the present paper, the potential of surface coatings to increase corrosion of internal combustion engine valves is discussed. The corrosion tests were carried out to study in simulated engine chamber environment the performance of Ni-, Co- and Fe-based materials used for plasma deposition. Hot corrosion tests were performed in air, sulphur dioxide containing atmosphere and in molten synthetic ash. The crucible-sorting test was used to simulate deposits on valve seats from residual fuel combustion which are responsible for rapid corrosion due to the presence of molten phase. The new alloys containing Ni and Co can be potentially applied as valve hardfacings.

An experimental study of the effects of thin thermal barrier coatings on the performance of a diesel engine was conducted. Results obtained from the engine with thermally insulated pistons were compared with the baseline engine data. Engine trials demonstrated good properties of both coating systems. Temperature and stress distributions within the pistons were evaluated analytically by means of the Cosmos/Works FEM code. Results of a road test on a gasoline-engine-driven car are also reported. The performance of the modified engine-driven car was found satisfactory. The ceramic coating did not produce observable knock in the engine, no significant wear of piston skirts or cylinder liners was found.

In numerous applications, hard-surfacing alloys must possess fair resistance to the abrasive–erosive action of hard particles contained in the transported media. This paper presents results of abrasion and erosion tests on deposits produced from NiCrSiB alloys. Microstructural investigations and wear tests have demonstrated the applicability of the alloys tested for hard-facing and reclaiming components made of high-carbon steel.

In this paper, the task of finding a solution to the erosion problem of the rotary fans used in cement plants is considered. The erosion tests were carried out on a range of materials, including heat-treated structural steels and alloy cast-irons. Weak correlation of the erosion resistance with the hardness of materials was found. The results point to the crucial effect of the cast iron matrix on the erosion resistance. The important parameter characterizing the erosion resistance of cast irons is the mean distance between carbide precipitates. The results show that the service life can be extended by several times through minor design alternations and the replacement of the materials applied hitherto by new materials.

W pracy przedstawiono wyniki badań mikrostruktury, struktury geometrycznej powierzchni oraz składu fazowego powłok natryskiwanych metodą płomieniowo-proszkową mieszaniną proszków AmI 3001.2 i UTP Exobond 2005. Wyznaczono parametry struktury geometrycznej i obliczono wymiary fraktalne profili powierzchni. Wykonano badania zużycia ściernego i erozyjnego powłok. Powłoki o wysokiej chropowatości wykazywały dużą odporność na zużycie ścierne. Wartość zużycia zależy od składu powłoki, struktury stereometrycznej oraz właściwości powierzchni rozdziału ziaren. Powłoki zawierające 30÷60% mas. UTP Exobond 2005 wykazują niższą wartość zużycia ściernego niż powłoki wykonane z materiałów bazowych. Intensywność erozji powłok cermetalowych zawierających poniżej 50% mas. UTP Exobond 2005 jest mniejsza niż intensywność erozji powłoki natryskiwanej UTP Exobond 2005. Microstructure and wear resistance of flame sprayed with the powder mixture coatings Abstract The paper presents results of investigations into microstructure, geometrical structure of the surface and phase composition of coatings flame sprayed with the mixture of AMI 3001.2 and UTP Exobond 2005 powders. Fractal dimensions and roughness parameters were evaluated. The tests of abrasive and erosive wear were done. High resistance to abrasion was revealed by high roughness coatings. Wear loss of coatings depends on coating composition, stereometric structure of the surface and intersplat surface properties. Coatings containing 30÷60% wt. UTP Exobond 2005 reveal lower wear loss in abrasion test compared to that of coatings performed from basic powders. Erosion intensity of cermet coatings containing less than 50% wt. UTP Exobond 2005 is lower than for coating sprayed with UTP Exobond 2005.

W artykule przedstawiono wyniki badań mikrostruktury powłok natryskiwanych metodą płomieniowo-proszkową mieszaninami proszków NiMoAl/ZrO2-30% CaO oraz NiAlMo/Al2O3-40% TiO2. Skład fazowy określono metodą XRD i wykazano, że w powłoce ZrO2 – 30% CaO występują fazy ZrO2 oraz CaZrO3, a w powłoce Al2O3-40% TiO2 – β tytanian glinu, korund, rutyl. Porowatość powłok cermetalowych zależała od składu proszków zastosowanych do natryskiwania. Wartości parametrów struktury geometrycznej powierzchni malały ze wzrastającą zawartością materiału ceramicznego. Dodanie do materiału bazowego tworzącego osnowę cermetalu niewielkiej ilości innego materiału zmienia mechanizm formowania powłoki. Microstructure of flame sprayed cermet coatings Abstract The paper presents results of microstructural investigations of coatings flame sprayed with the mixtures of powders nimoAl/ZrO2-30% CaO and niAlmo/Al2O3-40% TiO2. Phase composition was evaluated by means of the XRD method. The phases which appear in the ZrO2-30% CaO coating are ZrO2 and CaZrO3, whereas in the Al2O3-40% TiO2 coating – β aluminium titanate, corundum and rutile. Porosity of cermet coatings depends on the composition of powders used for spraying. The values of parameters describing the geometrical structure of the coating surface decreased with increasing ceramic content. The admixture of low content of other material to the matrix- creating base material changes the mechanism of the coating formation.

Functional performance of thermally sprayed coatings depends to a large degree on their surface topography. Surface topography of coatings was studied by analyzing numerically data sets aquired by contact profilometry. The effect of spraying method and powder composition was explored for a range of coatings. The effect of coating composition was studied for cermet coatings flame sprayed with mixtures of Ni-5%Al with ZrO2-30%CaO. To characterize the coating surface topography, multifractal analysis was performed. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)