Erosion-corrosion Process Research Articles

Understanding the role of alloying elements Cr, Ni in erosion–corrosion process of nuclear grade austenitic stainless steel 304 L by total reflection X-ray fluorescence

Stainless steel (SS) has gained an indispensable position as one of the most widely used industrial material. In nuclear industry, it is one of the technologically most important structural materials used in pressure tube, containment vessel and reprocessing-related applications. In fact, SS 304 L is the workhorse material of the reprocessing plant which faces the hostile conditions of acid, temperature as well as high radiation dose. These conditions can affect the erosion-corrosion behavior of the material and can lead to poor mechanical properties. This also affects the life of the reactor components. In the present study, a systematic work has been carried out to develop an in-depth understanding of the Corrosion Rates (CRs) with respect to the loss of major and minor elements from SS into the corrosive nitric acid medium using Total reflection X-Ray Fluorescence (TXRF). The effect of acid molarity as well as temperature, on the erosion-corrosion behavior of SS304L was studied. The TXRF studies have revealed that the CR was maximum in 2 M HNO3 and minimum in 8 M, showing that as the nitric acid molarity has an important role to play in the corrosion and as the molarity increases, the passivation of SS 304 L also increases. This observation was further corroborated with the concentrations of Fe, Cr and Ni, which had leached into the nitric acid medium. The role of alloying elements, Cr and Ni, in the passivation of SS was also studied. The effect of temperature showed that at 45 °C, the rate of corrosion was minimum, as compared to at 25 °C and 90 °C which reveals that the formation of chromium oxide passive layer was thermodynamically most favorable at this temperature.

Stainless steels as a solution for corrosion and erosion problems involving grains in agribusiness sector applications

Agricultural activities such as grain processing play a crucial role in Brazil's economy, contributing significantly to its gross domestic product (27.4% in 2021). The use of carbon steel equipment leads to considerable environmental and economic losses in agribusiness due to corrosion. This study explores the erosion-corrosion behavior of a dual-phase 11Cr and an 18Cr8Ni stainless steel (SS), compared to a mild (ASTM A36) and a high-strength carbon (AHSS) steel under conditions close to the agribusiness reality. The impact of corn particles as erosive component associated to pure water and chloride-containing environments was studied using a fog chamber, a topic until now unexplored in the literature. The methodology adopted is novel and explores the erosion-corrosion synergy in cumulative steps, aiming to shed light on the mechanisms of corrosion and wear that affect the materials in the agribusiness industry. The findings reveal that corn particles, despite their soft nature, can easily remove non-adherent corrosion products from the steel surface. In the deionized water medium, the impact of the soft particles can also shift the corrosion pattern of advanced high-strength steels from general corrosion to localized pitting damage reduzing the corrosion rates. The carbon and 11Cr steels showed the highest corrosion rates under the pure corrosion condition in both media. The erosion-corrosion process considerably reduced the corrosion rate, mainly in the deionized water medium for the carbon steels. An exception to this behavior was 18Cr8Ni steel, whose corrosion rates, however, were the lowest among the materials. Low-chromium stainless steel emerges as a cost-effective solution to erosion-corrosion challenges in the agribusiness segment.

Interaction of erosion and corrosion on high-strength steels used for marine dredging engineering

In this work, the erosion–corrosion performances of three high-strength steel samples: high manganese austenitic steel (HMnS), dual-phase steel (D-PS), and martensitic steel (MS), which are potentially used to construct marine dredged pipelines were investigated in comparison to the Q235 carbon steel. The corrosion-enhanced erosion (C-E) and erosion-enhanced corrosion (E-C) were electrochemically studied in conjunction with surface and subsurface characterizations. Results showed that the fracture of the steel extrusions induced by micro-cutting was the main erosion-corrosion feature under normal sand impacts. The C-E played a significant role in the erosion–corrosion process, which resulted in the dissolution of the work-hardening layer and facilitated the subsurface crack propagation, particularly for D-PS and MS. Although the general E-C rate was low, the concentration of the major anodes at the highly eroded area significantly enhanced the erosion process. Evaluating erosion resistance solely based on hardness is significantly limited. The twinning deformation of the austenite grain in HMnS effectively hindered the crack propagation during the erosion–corrosion. The addition of Al and Cr elements improved the erosion–corrosion resistance of high-strength steels.

Study on Simulation for Erosion-Corrosion in Petrochemical Process Piping

Erosion-corrosion is a damage to metal caused by relative motion at high velocity between metal surface and erosive/corrosive fluid, resulting from combined actions by mechanical erosion and electrochemical corrosion. Since petrochemical plants install numerous process pipes, especially involving complex oil refining processes and multi-phase transformation between solid, liquid and gas, the erosion-corrosion becomes one of major problems that disturb industrial work safety. So, it is important to create a mechanistic simulation model by fully considering various factors and closely simulating erosion-corrosion process.

Integrated Studies of Electrophysical Processes in Steam Turbines

The paper deals with comprehensive research in the field of electrization of wet steam flow in a turbine. The experience of the conducted studies on laboratory stands and full-scale objects (CHP and TPP) in Ukraine and the USA is introduced and generalized. It was shown that in the process of steam electrization, the charge density in the flow can reach very high values (an order of magnitude appears to be higher than in a thundercloud), and this phenomenon mainly has a negative effect on the turbine operation. Statistical data on the charge formation of the steam flow in the low-pressure cylinder of the turbine are presented. Results of the research to establish the main electrophysical factors of influence on the surface strength of the blade, such as electric fields, charge density and their polarity, are presented. The research results showed that such factors as the presence of a positively charged steam flow, constant and variable electric fields, which were most often recorded at operating turbines of CHPs and TPPs, significantly (by two or more times) intensify erosion-corrosion processes on the metal surfaces of the blades, thus reducing their working resource. Thermodynamic processes are studied both under conditions of natural electrification of a high-speed flow, which reduce the efficiency by about 0.3–0.35%, and under the influence of artificially created electric charges, which make it possible to increase the efficiency of the steam expansion process in the turbine by 2 or more percent. Various options of local input of electrical energy for steam ionization in the turbine are considered. At the same time, it is noted that for the practical implementation of these approaches, further careful design improvements and tests on model and full-scale installations are required. Water chemistry regimes are also considered in the context of their influence on the flow charge formation process, as well as on reliability and efficiency indicators of the turbine. Experimentally at an 800 MW turbine plant in the USA, it was shown that a change in the pH of the medium affects the intensity and polarity of the charge formation of the steam flow. The paper introduces the physical features of this phenomenon and notes the importance of these processes influence on the strength characteristics of the blades. Information on new methods and technologies that could lead to an increase in the operational efficiency and reliability of wet steam turbines, such as methods for input and removal of electrical energy into the flow; rational choice of water chemistry regimes; space charge neutralization, etc., is provided. These comprehensive electrophysical studies, considered in conjunction with thermal processes, can be characterized as a new scientific direction in the theory of steam turbines – thermal electrophysics.

Evaluation of erosion–corrosion process of Ti(C, N)-based cermets in acidic SiO2 slurry

This study investigates the erosion-corrosion process of Ti(C, N)-based cermets and compares it with WC-based cemented carbides in acidic SiO2 slurry. During the process, corrosion pits caused by corrosion expose the hard phase's sharp corners. The exposed corners crack, break and form debris due to the impact of SiO2's erosion. The slurry washes away the debris, and further corrodes the pits. Eventually, the binder surrounding the hard phase is destroyed, and the hard phase peels off due to the lack of bonding. In the initial stage, chemical corrosion is the main mode of destruction, followed by mechanical erosion. As the erosion time increases, the volume loss rate of cermets and cemented carbides also increases. The volume loss rate of medium-grained cemented carbide is the highest, followed by submicron-grained cemented carbide, and the smallest for the cermet. The erosion effect of SiO2 particles was more significant than the corrosion effects on volume loss in acidic SiO2 slurry.

Simulation of the Erosion-Corrosion Destruction Process of Steam Turbine Low-Pressure Cylinder Blades

This paper is devoted to the important problem of creating a method for predicting the intensity of erosion-corrosion destruction of the working blades material of low-pressure stages of powerful steam turbines, considering the complex physical processes that accompany the emergence, transformation of erosion-hazardous droplets and their interaction with elements of the flow path. The features of the construction of some existing erosion models are considered. The model that is developed at the Institute of Mechanical Engineering Problems of the National Academy of Sciences of Ukraine and based on a deterministic-statistical approach to its creation is analyzed in detail. The calculations performed during the research showed a satisfactory coincidence with the results of experimental tests by various authors, obtained on droplet impact stands, which contributed to the successful use of the model in creating a comprehensive method of predicting the wear of working blades. To do this, it was supplemented by the method of determining the parameters of the erosive environment based on the droplet movement equation, taking into account the size distribution law. Along with that, it is shown that the considered model, although it allows to carry out fairly accurate prediction of the development of erosive wear at the modern level, has difficulties in its construction due to the need to identify it from the data of full-scale experiments, the number of which is limited. It has been established that one of the important reasons for the discrepancies that arise is the failure to include of the electrophysical component of the processes occurring in a two-phase flow. In this regard, the results of comprehensive studies of steam electrization and its influence on the working processes of wet steam turbines are considered. It is shown that the change in the properties of the working medium as a functional erosive medium as a result of electrification causes a significant increase (relative to neutral wet steam) of electrochemical processes. At the same time, the kinetics of the damage accumulation to the metal surface layer changes due to the joint occurrence of several negative processes: droplet impact influence; electrochemical processes caused by mechanical and structural and chemical heterogeneity of the surface; hydrogen absorption; changes in mechanical properties under the electric field influence. It was noted that the contribution of hydrogen absorption to changes in mechanical properties is the greatest. According to a preliminary assessment, the complex negative droplet impact and electrophysical influence on the metal surface reduces the incubation period and intensifies the erosion-corrosion process by approximately 2 times

Investigation on Multiphase Erosion–Corrosion of Elbow in LPG Desulfurization Unit

Severe leakages of the elbow occur in the regeneration tower return pipeline of the LPG desulfurization unit, leading to the unplanned shutdown of the unit frequently over the period of four months. It is forced to apply additional steel plates to prevent the leakage. Elusively, it is found that the first wall contact with the fluid is fully eroded away in the vicinity of the bend, however, the walls of additional steel plates are intact. The clarification of this problem is required to ensure safe production. This strange phenomenon can be investigated by failure analysis and computational fluid dynamics (CFD) simulation. The failure analysis showed that the gas–liquid two-phase erosion–corrosion was the main cause of elbow leakage. The simulation shows that droplet erosion plays a dominant role in the erosion–corrosion process, and the elbow will leak in 4.3 months, which matches the actual situation very well. Furthermore, multiphase erosion–corrosion behavior was thoroughly investigated to expose the feature of the mentioned strange phenomenon. It was shown that when the corrosion holes are formed, the gas forms a fluid vortex in the holes. The vortex acts as flexible substrates, which plays a buffer layer to the droplet erosion, thus protecting the additional steel plate. The formation of the holes provides an effective way for elbow failure prevention.

Investigation of erosion-corrosion behavior of Q235B steel in liquid-solid flows

This work aims to investigate the erosion-corrosion behavior of Q235B steel in liquid-solid two-phase flows. The weight loss rate, surface morphology and electrochemical parameters of Q235B steel at different temperatures (20 °C, 30 °C, 40 °C) and flow velocities (6 m/s, 7 m/s, 8 m/s, 9 m/s, 10 m/s) were studied separately. The results show that the weight loss rate of Q235B steel specimens after erosion-corrosion increases with increasing flow velocity and temperature. For the erosion-corrosion process, the corrosion rates of specimens increase with increasing flow velocity. The results of surface morphology show that the circular pits with clear edges are distributed randomly over specimen surface at low flow velocity, but the pit edge becomes vague at high flow velocity. With temperature increasing, the erosion-corrosion damage became serious as shown by the aggregation of large and small pits on specimen surface. The working mechanism of erosion-corrosion is found to vary with flow velocity and temperature. The relationships among erosion-corrosion components are quantitatively represented and show that synergy dominates the progress of material loss. Corrosion enhances erosion that is a dominant component in the synergy. The inactions of erosion-corrosion can be described by ‘‘synergistic’’ and ‘‘additive’’ behavior. The results show that “additive” effect becomes more significant with increasing flow velocity but decreases with increasing temperature, while “synergistic” effect is not sensitive to flow velocity and temperature.

OPTIMIZATION OF EROSION–CORROSION BEHAVIOR OF NICHROME COATED 2205 DUPLEX STAINLESS STEEL USING GREY RELATIONAL ANALYSIS

Erosion–corrosion is a common mechanism in the degradation of systems in the mining, chemical, and petrochemical industries. Surface modification can help to reduce the detrimental effects of erosion–corrosion. This study uses the plasma spray process for coating nichrome on duplex stainless steel (DSS2205) to improve the surface characteristics. Erosion tests were performed to analyze the effect of parameters such as impact velocity (150, 175 and 200[Formula: see text]m/s), impact angle (30∘, 60∘and 90∘), and erodent particle discharge rate (2.5, 3.75 and 5[Formula: see text]g/min). According to the findings, the maximum erosion rate ([Formula: see text][Formula: see text]g/g) was found at a flow velocity of 200[Formula: see text]m/s and 30∘impact angle with a discharge rate of 2.5[Formula: see text]g/min. While the minimal erosion rate was observed at a low velocity of 150[Formula: see text]m/s, 90∘impact angle, and 5[Formula: see text]g/min discharge rate. Electrochemical polarization studies were carried out on the eroded specimens using a corrosive solution containing 3.5% NaCl. Corrosion potentials and current densities were estimated from polarization graphs using the Tafel extrapolation method. The erosion–corrosion properties of the samples were subjected to metallurgical characterization to evaluate the influence of nichrome plasma coatings to assess the potential causes of failure. The grey relational analysis (GRA) was further used for improving the erosion–corrosion process parameters and found the optimum solution as flow velocity of 150[Formula: see text]m/s, 30∘impact angle with a discharge rate of 5[Formula: see text]g/min. The validation test confirmed an increase of 20–30% in grade when using the optimum process parameters.

Erosion-corrosion behaviour of CoCrFeNiMo0.85 and Al0.5CoCrFeNi complex concentrated alloys produced by laser metal deposition

This study evaluates the corrosion and erosion-corrosion behaviour of two complex concentrated alloys (CCAs), CoCrFeNiMo0.85 and Al0.5CoCrFeNi, deposited by Laser Metal Deposition (LMD) onto a stainless steel substrate. The performances of the CCAs were compared to wrought stainless steel (UNS S30403) and carbon steel (P265GH). Erosion-corrosion testing was conducted using a submerged impingement jet test rig utilising a slurry comprising angular silica sand in an aqueous solution of 3.5%NaCl, adjusted to a pH of 4, impinging at 90°. Electrochemical monitoring was also undertaken in quiescent, flowing and solid-liquid conditions. The microhardness of CoCrFeNiMo0.85 was observed to be significantly greater compared to Al0.5CoCeFeNi due to the presence of intermetallic phases (identified by XRD) in the former. Although the CoCrFeNiMo0.85 CCA generally demonstrated superior durability than the CoCrFeNiMo0.85 variant, the relative performances of the investigated materials were observed to be dependent upon the hydrodynamic conditions. An important factor was the complex influence of corrosion on the overall erosion corrosion process. Indeed, when cathodic protection was applied, less distinct differences between the investigated alloys were evident in terms of the resulting pure mechanical damage. Post-test microscopy using SEM demonstrated that both CCAs experienced similar mechanical degradation mechanisms – sliding abrasion in low angle conditions and plastic deformation and micro-cracking in high angle conditions.

Investigation on wall thickness reduction of hydropower pipeline underwent to erosion-corrosion process

The present investigation was carried out to study the erosion-corrosion analysis in the hydropower pipeline of a Francis turbine. Testing was performed on a mild steel pipe having a diameter of 6 in.. An extensive set of experiments was carried out to test the properties of the erodent and the worn-out pipeline. Experiments were carried out using the sand-water suspension of concentration, ranging from 5000 to 20,000 ppm. The physical properties such as size and morphology of the sand particles as well as settling concentration of sand-water suspension were examined by the various bench-scale tests. The SEM-EDS techniques were used to study the morphological and chemical composition of the pipeline. Visual inspections depicted that the major deterioration occurred at the bottom half of the pipeline. Also, the lower surface of the pipeline seems underwent to high erosion and corrosion as compared to the upper surface of the pipeline. Results show that the erosion-corrosion process causes the wall thickness reduction of the horizontal pipeline. However, the properties of sand namely size, shape and static settled concentration of particles play a key role in the erosion wear of the pipeline. The solid particles of the sand eroded the pipeline material, which results in pits, craters, and cutting wear mechanisms on the pipeline surface. It can be said that the use of pipelines having an uneven hardness and lack of established inspection norms results in unexpected failures.

Problems of Hydrodynamic Corrosion in Multiphase Pipelines

This article analyzes the causes of corrosion and erosion processes in multiphase pipeline systems for collecting and transporting hydrocarbons from field technological pipelines of Azerbaijani fields. For different values of the initial pressure and diameter, the optimal values of the pumping range of heterogeneous well production were calculated taking into account changes in the viscosity and topography of the pipeline route. The influence of the fractional composition of mechanical impurities contained in oil on erosion–corrosion processes in infield pipelines was investigated taking into account the hydrodynamics of multiphase flows. Specific possible options for reducing the rate of dynamic corrosion in multiphase pipelines and utilization of separated mechanical impurities and water in field conditions are proposed.

Investigation of Erosion–Corrosion Resistance of Electroless Ni–P–Ti Composite Coatings

Electroless Ni–P–Ti composite coatings were prepared on AISI 1018 steel substrates by incorporating three different amounts of Ti nanoparticles into a Ni–P matrix. Erosion–corrosion tests were performed on AISI 1018 steel, Ni–P and Ni–P–Ti coatings. AISI 1018 steel exhibits the lowest erosion–corrosion resistance, while the highest erosion–corrosion resistance is achieved on coating containing 15.2 wt% Ti. For AISI 1018 steel, removal of oxide film by abrasive particles and severe pitting corrosion are the dominant erosion–corrosion mechanisms. For Ni–P coating, cracking and fracture of the coating are the prominent degradation mechanisms. However, micro-cutting, micro-ploughing and micro-indentation are the principal mechanisms for Ni–P–Ti coatings. Ti particles act as barriers during the erosion–corrosion process, which improve the erosion–corrosion resistance of the composite coatings.

Numerical Prediction of the Flow Structure Inside Components of Industrial Glass Furnace Systems

An important aspect in the glass production industry is related to the heat recovery of the combustion gases. It is usually obtained throughout the use of well-tested technologies, such as regenerative towers with refractory material. For an effective heat recovery, a good distribution of the flow rate at the entrance of the chambers is crucial. The use of Computational Fluid Dynamics (CFD) allows the detailed analysis of the gas evolution during the process; the same would be impractical with experimental measurements, due to prohibitive ambient local conditions. The CFD approach during the design phase typically considers CAD geometries without the level of details related to technological features of the actual installed configuration (i.e. sharp edges vs rounded edges). A brand new built furnace has blunt edges in every connection between 3D walls of refractory blocks. The above edges will be rounded by the erosion-corrosion process due to the harsh chemical/mechanical/thermal environmental conditions inside the plant components (i.e. regenerative chambers, connecting ducts, furnace). The purpose of this work is to evaluate the influence of the geometrical details of the CAD (with focus on the edges connecting adjacent walls), due to technological or erosion aspects, on the flow structure in the furnace components.

Synergistic Erosion-Corrosion Behavior of API X120 Steel

The corrosive nature of fluid (oil and gas) and the presence of solid erodent particles in it causes the pipelines to experience severe erosion and corrosion during the transportation process. In this study, erosion-corrosion behaviour of API X120 steel was investigated using aluminium oxide particles (60 µm) as erodent and 3.5% (wt. %) NaCl aqueous solution saturated with carbon dioxide as a corrosive medium. Effect of particles speed at an impact angle of 90° and the synergistic effect of erosion-corrosion were investigated using weight loss, potentiodynamic polarization technique, and surface analysis. During the corroison-erosin process, the formed iron carbonate layer (during corrosion process) is removed by the erosive erodent particles (erosion process) which results in high corrosion rate and high surface roughness. Furthermore, during the erosion-corrosion process, a significant effect of corrosion on erosion at lower particle's speed is noticed while at higher particle speed erosion has a dominant influence on the corrosion as identified in the Synergy/Total erosion-corrosion ratio (S/T ratio). Finally, our results indicate a simultaneous activation of erosive and corrosive phenomena during erosion-corrosion of API X120 steel.

Силурийский эмерсивный рубеж на территории Южного Притиманья (Пермский край)

At the base of the Silurian deposits in the Southern Rassolnaya Deposit, ventfacts considered as an indicator formations of deserts with a predominance of wind erosion (corrosion) processes were first discovered. In this work, the systematization of the found ventfacts was carried out, their morphology was revealed, and it is concluded that the most numerous group among the Aeolian polyhedra is the group of pyramidal ventfacts. Among the latter, the pyramidal trihedrons, otherwise known as dreikanters, are the most common. From the point of view of lithology, ventfacts are quartzite sandstones with relics of hydromicas cement, the structure of which is dominated by a cementless contact connection of quartz grains and fragments of various rocks. According to the structural position of the layers of rocks containing windmills, deposits of the Ordovician and Silurian systems are distinguished in the geological section. A mineralogical study of this section was conducted analyzing the mineral associations of the heavy fraction of lithological samples. The conclusion about possible ventfacts formation time as the border of the Ordovician and Silurian was made. To denote the time and facies boundaries of the emersive phase, the concept of the emersive frontier (or boundary) is introduced by analogy with the term mineralogical boundary. This frontier is taken by the author as the upper (Silurian) emersive boundary, after which there is a drastic change in the tectonic situation in the region. Based on the results of the study, a paleogeographic reconstruction of the Eastern margin of the East European platform on the Silurian emersive frontier is proposed, which may be associated with the Aeolian type of diamond placers of the Silurian intermediate reservoir in the Southern Cis-Timan.

Performance Evaluation of a Potent Green Inhibitor on 6061 Aluminum Alloy Under Liquid/Solid Jet Impingement

Erosion corrosion inhibition of 6061 aluminum alloy in artificial sea water in a jet impingement rig was studied using eco-friendly green inhibitor glucose amine sulfate. Hydrodynamics plays a major role in the performance of inhibitor. Out of the many techniques available, jet impingement is the one which mimics the industrial conditions and hence used in the current investigation. Potentiodynamic and electrochemical impedance techniques were employed for corrosion and inhibition studies. Experiment was conducted by varying the flow rate and temperature at an impingement angle of 90°. Surface study was done using SEM and variation in the morphology as a result of erosion corrosion and inhibition was discussed in detail. The results indicated that the erosion corrosion process is both charge transfer and diffusion controlled and the mechanism of erosion corrosion changed with change in the experimental conditions of temperature and velocity. The increase in the flowrate demonstrated an increased protection efficiency. Glucose amine sulfate inhibited the erosion corrosion with an efficiency of 54% for the addition of 750 ppm, for the flow rate of 4 lpm at the temperature of 313 K. Surface morphology studies clearly demonstrated the efficacy of glucose amine sulfate in controlling the erosion corrosion of 6061 aluminum alloy.

Interaction between pitting corrosion and critical flow velocity for erosion-corrosion of 304 stainless steel under jet slurry impingement

The interaction between pitting corrosion and critical flow velocity (CFV) for erosion-corrosion of 304 stainless steel under slurry impingement was investigated through electrochemical tests, scanning electron microscopy and X-ray photoelectron spectroscopy. The results show that pitting corrosion affects the precise determination of CFV using the potentiostatic polarization tests, while CFV just corresponds to the case of the highest pitting corrosion resistance in erosion-corrosion process. This interaction is explained in terms of the properties of surface film. Furthermore, the guidance for quick determination of CFV is proposed and the significance of CFV in evaluating the erosion-corrosion resistance is highlighted.

Considerations regarding WC-cermets depositions by HVOF and ESD techniques used for reinforced steel components for geothermal turbines

The cumulative effect of erosion-corrosion process in geothermal turbines results in significant damages, especially for rotors and turbine blades; the degree in which they are affected depends on steam temperature, mechanical impact and the geothermal composition of the substances dissolved in steam. Layer composite materials are a feasible option to improve the erosion-corrosion resistance and the durability of turbine components. There cermet powders containing tungsten carbide are used for High Velocity Oxy-Fuel (HVOF) spaying and for Electro Spark Deposition (ESD) to obtain graduate microstructure and to form local hard structures. Both techniques by WC-cermet depositions were found to be most suitable to improve wear resistance, to repair rotors and blades and to provide possible life extension of geothermal turbines. The paper presents a comparative assessment of tungsten carbide and the technological parameters used for HVOF and ESD cermets layers depositions. Also, the work presents the analysis of the micro chemical composition of the microstructure, the micromechanical characterization and erosion-oxidation resistance of HVOF and ESD coatings using WC-cermets on steel substrates. The experimental procedure involved X-ray diffraction of the samples, micro mechanical tests and SEM investigations to provide specifically information about micro-morphological modifications and grade of adhesion of protective layers.