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Soil preparation tools are subject to severe abrasion. The wear resistance of various industrial components can be improved using the hardfacing technique. The improvement in hardfacing wear resistance depends on the microstructure, i.e., the chemical composition of the alloys, the method of overlay, and the parameters of the selected process. The Plasma Transferred Arc with Powder (PTA-P) welding process is interesting as a hardfacing technique since it promotes very low dilution of the substrate in the coating. In this article, the PTA-P welding process was used for the deposition of Fe-Cr-C-based hard coatings with the addition of vanadium onto cheap and relatively soft low-carbon steel substrates. Rubber-wheel abrasion tests were performed to compare the abrasion resistance between commercial anti-wear steel and weld-deposited Fe-Cr-C-V hard coatings. In addition, the microstructure, dilution, and wear mechanisms were investigated. The dilution of the coatings affected the microstructure, in particular, the free mean path of the vanadium carbides, but it only affected abrasion resistance when the wear mechanism involved rolling abrasion. The deposited coatings proved to be at least three times stronger than a commercial abrasion-resistant steel due to the distribution and morphology of the vanadium carbides formed in the coatings.

Different techniques are usually employed to evaluate the mechanical properties of arc-sprayed coatings. In many situations, comparing properties is complex, and values extracted from tensile tests are required for structural projects. X6CrNi18-8 stainless steel and molybdenum were sprayed onto a mild steel substrate using the electric arc thermal spray technique to discuss this issue. After a detailed microstructure characterization, tensile tests were performed on both coatings to determine the yield strength and total elongation. Easy techniques were also applied: Vickers hardness and Charpy impact test. Tensile tests have shown that applying coatings increased the steel substrate’s total elongation. Molybdenum coating presented a higher impact resistance than the X6CrNi18-8 one, resulting in no correlation between elongation and Charpy values. On the other hand, correlations between hardness and yield strength were identified, opening a discussion on the effects of the microstructure and type of test used.

The study evaluates the mechanical and wear properties of LM26 alloy and its hybrid composites with silicon carbide (SiC) and nickel-coated graphite (Ni-Gr). LM26 aluminum alloy is generally known for its high strength, wear, and corrosion resistance compared to similar materials such as zinc and magnesium. The effect of Ni-Gr was studied, with 2 wt.% was found to provide the best mechanical properties. LM26 composites reinforced with varying percentages of SiC (0 to 30 wt.%) showed the best properties at 20 wt.% reinforcement after fabrication using a bottom pouring type stir casting setup (Two step feeding method). Evaluation of five hybrid LM26 composites through tensile strength, elongation, hardness, impact, porosity, and thermal studies showed that the LM26/2 wt.% Ni-Gr/20 wt.% SiC configuration showed the best filler composition for improved strength. Sliding wear evaluation using experimental and Taguchi analysis was performed at different configurations to identify the best wear resistance. Microstructure studies showed the presence of Ni-Gr particles forming coatings and temperature playing a significant role in the progression of the wear rate. Furthermore, the hybrid composite with 20% SiC and 2% Ni-Gr reinforcement showed the best wear resistance.

Gas tungsten arc welding (GTAW) technology is widely used in industry and has advantages, including high precision, excellent welding quality, and low equipment cost. However, the inclusion of a large number of process parameters hinders its application on a wider scale. Therefore, there is a need to implement the prediction and optimization models that effectively enhance the process performance of the GTAW process in different applications. In this study, a five-factor five-level central composite design (CCD) matrix was used to conduct GTAW experiments. AISI 1020 steel blank was used as a substrate; UTP AF Ledurit 60 and UTP AF Ledurit 68 were used as the materials of two tubular wires. Further, an artificial neural network (ANN) was used to simulate the GTAW process and then combined with a genetic algorithm (GA) to determine welding parameters that can provide an optimal weld. In welding experiments, five different welding current levels, welding speed, distance to the nozzle, angle of movement, and frequency of the wire feed pulses were used. Using GA, optimal welding parameters were determined: welding current = 222 A, welding speed = 25 cm/min, nozzle deflection distance = 8 mm, travel angle = 25°, wire feed pulse frequency = 8 Hz. The determination coefficient (R2) and RMSE value of all response parameters are satisfactory, and the R2 of all the data remained higher than 0.65.

This review presents the possible strategies to increase the wear resistance of hardfacing alloys based on metallic matrix and second hard phase’s coupled design. As the wear resistance is not an intrinsic property of material, the results of many wear tests are discussed in light of the interaction between mechanical properties and wear severity, which is dependent on the microstructure. These strategies are based on the hardness increase, considering the kind and size of the second hard phase, the fracture toughness, and the dilution level of hardfacing. The guidelines provided for designing better the hardfacing alloys for usual abrasion conditions depending on the volume fraction of the second hard phase. Resumo Esta revisão apresenta possíveis estratégias para aumentar a resistência ao desgaste de revestimentos duros, baseado no projeto conjunto de matriz metálica e segunda fase dura. Como a resistência ao desgaste não é uma propriedade intrínseca do material, os resultados de vários ensaios de desgaste são discutidos à luz da interação entre propriedades mecânicas e severidade de desgaste, o que é dependente da microestrutura. Estas estratégias são baseadas no aumento de dureza, considerando o tipo e tamanho da segunda fase dura; a tenacidade à fratura e o nível de diluição do revestimento. As diretrizes fornecidas para o melhor projeto de ligas de revestimentos duros para condições usuais de abrasão dependem da fração volumétrica de segunda fase dura.

Abrasive wear is highly dependent on the characteristics and properties of abrasive particles. Their hardness and size can define the severity of abrasion in terms of wear rates. Typically, critical values have been empirically determined to define the transition between mild and severe wear. This review aims to update some of the issues related to these critical values and their relations to abrasive wear. After presenting the current state-of-art, the following items are discussed: a) the scratchability of materials; b) the particle fragmentation associated with size effects; and c) description of abrasion severity.

Purpose This paper aims to present a proposal for evaluating the coefficient of friction (COF), under a reciprocating test that considers the energy dissipated by the friction force. In addition, this new parameter is compared to average COF, which is often used to evaluate COF in reciprocating tests. Design/methodology/approach Samples of compacted graphite iron were extracted directly from an internal combustion engine block. The piston ring used was a nitrided martensitic stainless steel with an asymmetrical profile, and the lubricant oil was the SAE 30 CF, controlled at 40°C. Different testing conditions were carried out in a CETR-UMT-Bruker tribometer, varying loads between 25-125 N, frequencies between 1-12.5 Hz and track length between 3-10 mm. Three maps comparing the average COF and the energetic definition were built, allowing to discuss their similarities. Findings In general, both parameters had similarities especially for low frequencies and small tracks. However, for test conditions that imposed higher accelerations (i.e. longer track lengths and higher frequencies), the energetic COF (COFe) was lower than the average COF (COFa) and presented better agreement in Stribeck-like curves – independent on the experienced lubrication regime along the stroke. As the COFe can be interpreted as a weighted average of instantaneous COF in relation to in-track displacements, an immediate consequence is that instantaneous COF closest to mid-stroke is considered more significant. Furthermore, perturbations associated with the intrinsic accelerations of the movement test are minimized in the COFe formulation. Originality/value The energetic COF parameter (COFe) is presented and compared to the average COF. The new parameter presented less data dispersion and is attractive to evaluate the COF behavior in reciprocating tests, as its formulation minimizes perturbations associated with the intrinsic accelerations of the movement (mainly in the initial and final part of the track where the acceleration has its greatest magnitude). Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0324

Herein we compare seven models of erosion of ductile materials, considering various combinations including cutting and deformation components of wear. The models were fit to three independent sets ...

Two grades of duplex stainless steel, SAF 2205 and SAF 2507, were nitrided using an active screen plasma process carried out at 380 °C for 10 h and were characterized in terms of microstructure and hardness. Wear resistance was assessed by means of linear scratch tests, using loads below and above the critical load. Potentiodynamic polarization was used to analyze corrosion behavior in 0.6 M NaCl solution. X-ray diffractometry showed expanded austenite formation in all nitrided samples. The super duplex steel SAF 2507 showed much better scratch resistance, with low friction coefficient and greater toughness, as judged by the pattern of superficial cracks when it was tested above the critical load. The corrosion behavior of steels was also different, mainly in the active region, and nitriding had a more beneficial effect upon SAF 2507. The potential relative to the transpassive region was practically unaffected by the nitriding.

A constant challenge in the automotive industry is to find ways to reduce the friction. Reductions in the weight of components can play this role, but for using smaller thickness in the engine blocks more resistant materials should be employed. The present investigation discusses the tribological performance of two cast irons used for manufacturing engine blocks, grey cast iron (GCI) grade FC250 and compacted graphite iron (CGI) grade GJV450, and the effect of two different thicknesses – 3.9 ( ± 0.6) and 7.4 ( ± 0.4) mm – on their friction and wear behaviors assessed in a ring-on-cylinder test under mixed lubrication. The tests were 8-h long with a normal force of 75 N, a stroke of 10 mm and a frequency of reciprocating movement of 5 Hz. A new parameter was introduced for evaluating the tribological performance, called Tribological Merit Index (TMI), which considers the coefficient of friction (COF) and the changes in the surface topography, determined using a 3D optical interferometry. The thickness of the samples did not affect significantly the COF values. Nevertheless, the best result in terms of the friction behavior was obtained for the CGI-thin sample (0.111). For the contact area estimated by the topographical parameters, the thickness was not relevant just for the samples of lamellar cast iron; and the best result,was obtained for the CGI-thin. Considering the TMI parameter, a ranking could be established, from the best to the worst tribological performance: i) CGI-thin; ii) CGI-thick; iii) GCI-thick; and iv) GCI-thin.

Manufacturing processes imply different ranges of surface roughness, such as found in dental components. These surfaces have vital roles from a clinical perspective, including essential biocompatibility, bacterial adhesion, and prosthetic retention. However, the relationship between the surface topography and these characteristics can be more detailed, especially in texture analysis. For this purpose, three specimens were studied: (i) Ti-6Al-4V alloy manufactured by wire electro-discharge machining (WEDM); (ii) Ti-6Al-4V alloy manufactured by WEDM followed by electropolishing (WEDM + EP); and (iii) a seating platform of dental implant CNC-machined, manufactured in Ti–CP. Surface topography was analyzed through optical interferometry, using the following parameters: Sq (root mean square), Sp (max peak height), Sv (max valley depth), Ssk (skewness), Sku (kurtosis), and Str (texture aspect ratio). The application of the electropolishing process was sufficient to remove all irregularities left by WEDM, rounding the peaks and valleys, meaning a reduction of 69% in Sq value. On the other hand, the deviations in the seating platform’s height distribution can be considered critical for generating a misfit between the implant–abutment pair. In this case, electrochemical machining is recommended for this surface, instead of grinding processes.

Samples of AISI 409 were thermochemically treated by the Solution Heat Treatment after Plasma Nitriding (SHTPN) process. SHTPN process consisted of a nitriding step followed by solution annealing at 1100 °C and rapid cooling down to room temperature. The second cycle of quenching (950 or 1050 °C), followed by tempering (250, 450, or 650 °C), was performed sequentially to SHTPN. Lubricated reciprocating tests were employed to analyze friction and wear behaviors. A bearing steel ball was used as a counterpart. The analysis of worn surfaces was assessed using optical interferometry and depth-sensing indentation. The last technique allows determining the work hardening caused by the wear process. Friction behavior was related to the deformation component: the higher the hardening, the higher the friction coefficient. Abrasion is the primary mechanism observed in all specimens, but there is a transitional behavior that depends on the original hardness of the surface. Samples with a similar hardness of bearing ball presented delaminated regions caused by highly deformed thin layer fatigue. Amongst SHTPN conditions NS-Q950-T2 and NS-Q1050-T2 presented the best balance of wear and corrosion performances.

Significant research has been done to improve the wear properties of the components used in internal combustion engines. Excessive wear is observed in components such as cylinder liners and rings, which can lead to lower volumetric efficiency of the engine, increase oil consumption, polluting emissions, and scuffing related issues. Since tribological systems in internal combustion engines are complex, the different wear mechanisms involved need to be investigated to improve the life of components. Cast irons are commonly used for engine components, especially compacted graphite irons (CGI) for piston rings and gray cast irons (GCI) for cylinder liners. This work aims to evaluate the tribological behavior of two different microstructures of CGI (pearlitic and ausferritic), sliding on pearlitic GCI. The samples of CGI with different microstructures and hardness were evaluated in a short-stroke reciprocating sliding tester, using Petronas Urania SAE 30 API CF lubricant oil at 100 °C for four hours. The characterization of worn surfaces was made using a scanning electron microscope (SEM) and 3D roughness measurements. The coefficient of friction (COF) comparison between the two CGI microstructures showed very similar results with COF = 0.11. The pearlitic CGI showed more severe wear than the austempered one, confirmed by SEM images and the difference in topography parameters before and after the tests. Phosphorus, sulfur, and zinc were detected by EDS analyses in the samples' worn-out regions, indicating the formation of tribo-films, which was further confirmed by the friction tests.

The wear of tools in rock excavation is a challenging and costly issue. To predict the added costs arising from wear, field and laboratory investigations can be conducted during the early stages of a project. Accordingly, a measure of particle abrasivity is needed. Abrasivity is defined as the capability of different kinds of soils and rocks to cause abrasive wear of metallic surfaces. The Cerchar abrasiveness test is a well-recognized lab test for assessing rock abrasivity. The Cerchar Abrasiveness Index (CAI) is determined by measuring the crater diameter [mm] produced by a conical steel stylus moving under a fixed load and sliding distance. Many authors have been trying to correlate CAI with rock properties, but no consensus has been achieved. The main reason for this difficulty arises from the effects of the microstructural complexity of rocks and their tribological response. This investigation proposes a new approach based on the use of a scanning electron microscope to identify the wear mechanisms acting on the Cerchar stylus (AISI A2 tool steel) during testing, and comparing these observations to the corresponding CAI values for nine different rock types (0.1

Surface roughness parameters of mechanical components are sensitive to systematic errors, which can cause significant deviations in their values. These parameters are commonly used for manufacture controlling or even for tribological applications, such that their variations may lead to miscarried interpretations or mistaken conclusions. This investigation aims to analyze the error of light beam incidence, caused by eventual mal-positioning of the sample. Concave surfaces produced by boring and honing processes were evaluated by optical interferometry method. For this study, two samples of compacted graphite iron, extracted from a cylinder liner of a block of an internal combustion engine with a nominal diameter of 83 mm, were studied. The average and standard deviations values of chosen 3D roughness parameters – Sa, Sq, Sk, Spk, Svk, Spq, Svq, Smq, Sds, Ssc, and Sdq – were determined. The equipment utilized for the measurements was Talysurf CCI Lite, integrated with the software Talymap Platinum. Two procedures of measurement were realized for each type of surface. In the first, reflection angles of 0; 1.38 and 2.76° were imposed. Then, additional measurements were performed following the same principles, except that this time the reflection angle was corrected by the use of a shim, ensuring the perpendicular incidence of the light beam in the surface through evaluation of the fringe spreading during the measurement set-up. The bored surface was more sensitive to the effects of light beam incidence than those observed for honed one, confirmed by the general analysis of 3D images, by the variations in Sq parameter and those of Sk family. Within the parameters of family Sk, the robustness of Svk was remarkable for both investigated surface finishing. Together with this result, the Sp map analysis showed that the predominance of peaks in the bored surface was responsible by a more accentuated effect of light beam incidence, intensified to their greater values of Sq. The hybrid parameters were the most affected by the light beam incidence angle on the concave surface, suffering significant alterations for a reflection angle of just 1.38°. In addition, the correction of incident angle resulted in any significant divergence for any surface roughness parameter.

It is well-known that diesel engines generate soot during the combustion process, leading to a higher level of pollutant emissions and severe wear of contact surfaces in relative motion, resulting in worse engine performance. Carbon black has been used in laboratory wear tests to simulate soot in engine components such as piston rings and cylinder liners. However, there are still many questions to be answered, especially concerning the interaction between the particles, lubricants, and surface topography in contact. In the past years, compacted graphite iron (CGI) has been substituting grey cast irons in engine blocks because of its improved mechanical properties, resulting in thinner walls for lighter blocks and improving engines' performance. However, CGI's tribological behavior of higher strength grades has been scarcely studied due to its production cost and complexity. In the present study, two CGIs of high strength (JV450 and JV500 – ISO 16112/2017) were used as cylinder liners on ring-on-cylinder lubricated wear tests a CETR-UMT-Bruker tribometer. The cylinders' surfaces were honed to a plateau finishing, and the counterbody used was a commercial compression ring of nitrided stainless steel. Carbon black particles were added to commercial SAE CF-30 lubricant, simulating the presence of soot. The testing load and oil temperature were 175 N and 100 °C, respectively, creating a severe wear condition. Roughness measurements using interferometry were performed on the worn surfaces to compare with the plateau's topography and roughness parameters honing texture. The variation of structure height was used as the indicative of liner wear. Results showed almost the same coefficient of friction (COF) for all tested conditions. Still, the reason for each case was different, the ejection of graphite during sliding being more critical for JV450 iron. The carbon black was able to change the contact conditions. The high-strength GJV500 iron performed better, considering a tribological merit index (TMI), less sensitive to the presence of carbon black in the lubricant oil.

Rolling contact fatigue (RCF) of a nitrided ductile cast iron was investigated. Flat washers machined from a pearlitic ductile cast iron bar were quenched and tempered to maximum hardness, ground, polished and divided into four groups: (1) specimens tested as quenched and tempered; (2) specimens plasma-nitrided for 8 h at 400 °C; (3) specimens plasma-nitrided and submitted to a diffusion process for 16 h at 400 °C; and (4) specimens submitted to a second tempering for 24 h at 400 °C. Hardness profiles, phase analyses and residual stress measurements by x-ray diffraction, surface roughness and scanning electron microscopy were applied to characterize the surfaces at each step of this work. Ball-on-flat washer tests were conducted with a maximum contact pressure of 3.6 GPa, under flood lubrication with a SAE 90 API GL-5 oil at 50 °C. Test ending criterion was the occurrence of a spalling. Weibull analysis was used to characterize RCF’s lifetime data. Plasma-nitrided specimens exhibited a shorter RCF lifetime than those just quenched and tempered. The effects of nitriding on the mechanical properties and microstructure of the ductile cast iron are discussed in order to explain the shorter endurance of nitrided samples.

Martensitic stainless steel is a potential material class for selection in some tribological systems, particularly those subjected to wear by hard particles and corrosion. To improve its mechanical resistance, without loss of corrosion performance, surface treatments such as low-temperature nitriding and carburizing have been systematically employed. In this context, this paper studied martensitic stainless steel samples subjected to different plasma-assisted treatments, in the case the plasma nitriding and plasma carburizing. The treatments were carried out at temperatures of 300, 350 or 400 °C, for different times, aiming to compare the scratch resistance of the treated surfaces. Specimens were initially characterized using X-Ray diffractometry, micro and nanohardness measurements. Scratch resistance was performed using the constant load mode for two levels, 8 and 15 N. All worn tracks were evaluated using optical interferometry, to get information about the widths and depths of track profiles. Worn surfaces were analysed using scanning electron microscope, revealing tensile cracks on the surface of nitrided samples. The friction coefficient and the wear resistance were analysed and related to the geometry of scratches, which was associated to the micro-mechanism of wear. Despite the high hardness and low friction coefficient achieved using nitriding treatment, the global performance of carburized samples could be considered as more suitable, because the carburized case significantly minimized the cracks formation. Therefore, plasma carburized martensitic stainless steel can be considered an adequate combination for corrosion environments subjected to wear.

The superficial characteristics of honed surfaces are relevant for the tribological performance of cylinders of internal combustion engines (MCI). Recent studies found a correlation between the occurrence of the phenomenon called folded metal and the presence of graphite of cast irons. However, the honing process tends to overlap the graphite, such that an application of a technique to remove a thin layer of material, exposing the graphite, would be useful. This paper aims to determine the best condition, of electric potential and time, for the exposition of graphite in honed surfaces using a technique of electrolyte polishing. The polishing was made on the concave surface with aid of a polishing mask developed for this matter. Samples of honed cylinders were removed from MCI manufactured using a compacted graphite iron. The characterizations were done through metallography and white light interferometry. To determine the ideal condition, several conditions of polishing were tested. For the verification of the repeatability, five repetitions were performed with the best condition. The results showed satisfactory repeatability, with an exposition of graphite and the matrix etching. The roughness of the polished region presented considerable uniformity, with a significant change of roughness in comparison to the honed surface. Furthermore, removal of the characteristic topography of the honed surface was observed. The layer removed showed little variation in depth along the polished region, with values close to 5 μm. This value accomplishes the demand of layer removal for the exposition of subsurface graphite. Keywords: Electrolyte polishing; Compacted graphite iron; Honing.

The hydroerosive grinding is one of the processes to manufacture diesel injection nozzles, being responsible for finishing injection holes. The process made use of an abrasive fluid under high pressure into these channels. Its efficiency depends on the physical properties of the abrasive fluid. Based on a previous investigation, this study verified the possibility of using a different particle size distribution of boron carbide to improve the process efficiency. All experiments were carried out in an industrial environment. The variation in process efficiency was compared with the maintenance of the viscosity along the production, and at the same time, the concentration of solids was constantly monitored. The alteration of particle size distribution was not suitable, causing an increase in the average particle size. In addition, we have verified that the concentration of solids presented a major influence on the process efficiency, being the lower the concentration, the lower the efficiency.

O material de estudo deste trabalho foi o aco inoxidavel 15-5PH, que possui alta resistencia mecânica e a corrosao. Para aumentar ainda mais essas caracteristicas, comumente realiza-se tratamento termoquimico de nitretacao a plasma. Neste trabalho foi realizado o estudo de resistencia ao desgaste deste material, visando determinar qual tempo e temperatura de nitretacao a plasma conferem melhores resultados sob este aspecto. Para tal, foram utilizadas amostras e alguns resultados (dureza do nucleo e camada composta, perfil de microdureza da camada nitretada, dentro outros) da dissertacao de mestrado do Prof. Dr. Euclides Alexandre Bernardelli, o que realizou a nitretacao por tempos de 2,4 e 6 horas e temperaturas de 663, 713 e 763K, sendo que a amostra a 713K so foi analisada com 4 horas de nitretacao. Este estudo tambem se baseou na elaboracao de testes de riscamento (Scratch Test) nas amostras nitretadas e em estado de fornecimento, a fim de determinar a carga critica, coeficiente de atrito, volume desgastado, fator de abrasao e perfis 3D e 2D dos sulcos de riscamento atraves de interferometria otica e analise em microscopico eletronico de varredura. Em relacao a resultados, foi obtido que, exceto para a amostra com menor tempo e temperatura de tratamento, todas as amostras nitretadas obtiveram melhores resultados de desgaste em relacao ao fornecimento. Com a aumento de tempo e temperatura de nitretacao os mecanismos de desgaste evoluiram de deformacoes plasticas e adesao para corte.

Linear scratch tests were performed on polished surfaces extracted from different cylinder liners, manufactured in lamellar and compacted graphite irons. The effect of wall thickness was evaluated, by extracting samples from regions equivalent to two levels of thickness. Scratch geometry was analyzed using 3D interferometry, in terms of pile-up proportion and widths of tracks, and wear mechanisms were revealed under a scanning electron microscope. Overall friction coefficients could be related to the deformation of metallic matrix and the graphite count, while graphite affected the scratch geometry, especially their widths along the sliding distance. The larger variation and higher friction amongst the tested materials were observed for compacted graphite iron, extracted from the thick wall. The observed wear mechanisms were also verified in worn components subject to abrasive environments.

This investigation explores the effect of some input cutting variables of boring process—cutting speed, feed rate, tool nose radius and coolant pressure—on the surface integrity of super duplex stainless steel grade SAF 2507. The surface integrity was evaluated by means of 3D surface roughness, residual stresses determined by X-ray diffraction, and work hardening using Vickers hardness. The most significant variable was the feed rate, which affected both the roughness parameters and the residual stresses. For the low level of feed rate and the higher nose radius tested the machined surfaces could be identified as Gaussian in terms of surface heights distribution with an insignificant work hardening due to the machining. In this fashion, a best combination of boring conditions could be indicated to reach the lowest roughness values with Gaussian surfaces and compressive residual stresses with a low level of work hardening.

The use of two-dimensional shape parameters to characterize abrasive particles is a potential approach to express their angularity. Nevertheless, in sliding abrasion, especially in pin abrasion testing, these descriptors could not be suitable for characterizing severe wear of engineering materials such as steels and cast irons. This work compares the applicability of two-dimensional shape parameters in describing severe wear of metals in recent pin abrasion tests with cases where they could have been correlated with the wear rates. Considering these aspects, this work puts in evidence the importance of clogging occurrence and the coated paper structure for a carefully application of shape parameters. In addition, it is proposed a possible relation between the shape parameters and one of the components of the abrasion factor.

Compacted graphite iron is an interesting material class for automotive applications. CGI-450 grade cast iron was subjected to various surface treatments: plasma nitriding (PN), laser hardening (LH), and PN followed by LH (PN+LH). The resulting tribological behaviors were evaluated by means of linear scratch testing under progressive loading (40–70 and 70–95 N). The PN+LH treatment yielded the lowest friction coefficient and shallowest scratching. In this case, the outermost layer was composed of oxide phases (Fe2O3 and Fe3O4), underlain by a compound layer (oxides + nitrides + martensite) and a high-resistance martensitic layer with accompanying nitrides and carbides. These underlying layers provided high load capacity for the external layers, allowing them to function as solid lubricants.