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Ni60-WC coatings with different WC contents on the bucket tooth substrates were pre- pared using laser cladding technology. Their abrasive wear properties were assessed using the dry sand rubber wheel test system. The substrate and the hard-facing layer were tested for comparison. The results showed that the hardness of the Ni60-WC coatings increased with the increase in WC content. The wear resistance of the bucket tooth substrate was greatly improved by hard-facing and laser cladding Ni60-WC coatings. The wear rate of the hard-facing layer was reduced to 1/6 of that of the tooth substrate. The wear rate of the laser cladding coatings with 20–40 wt.% WC was similar to that of the hard-facing layer. It is worth mentioning that the wear rate of the coatings with 60–80 wt.% WC was only 1/4 of that of the hard-facing layer. Micro-cutting with surface plastic deformation was the main wear mechanism of the substrate to form narrow and deep furrows. The wear mechanism of the hard-facing layer was mainly plastic deformation with a wide groove, and the surface cracks promoted the removal of the material. The removal of the binder phase caused by micro-cutting was the main wear mechanism of the laser cladding Ni60-WC coatings. However, the hard phase of WC hinders micro-cutting and plastic deformation, which improves the wear resistance of the coating. [ABSTRACT FROM AUTHOR]

In this work, the Metal Inert Gas (MIG) welding process is used for depositing the Inconel 718 over the base substrate of Stainless steel 321. The optimal welding conditions like 50% overlap, Direct Current (DC) plus mode with a pulse on time (1–5 s), frequency (0.25–1 Hz), peak current (120 A), base currents (60% of peak current), and speed (150–350 mm/min) are used for the successful hard-facing. The quality of the hard-facing is analyzed by conducting microstructural studies, tensile tests, microhardness, wear behavior, and electrochemical studies. Post-processing for wear and electrochemical studies is done by Scanning Electron Microscope SEM–EDX analysis. Microstructural studies revealed the presence of columnar dendrites and equiaxed at the top of the hard-faced layer. Hard-faced layer depicts the highest ultimate tensile strength of 772 N/mm2 with an elongation of 31.50% due to the support of Nickel components. The presence of the voids and dimples is identified from the SEM fractography. The maximum hardness value of 212 HV 0. 5 is measured at the top of the hard face layer. The microhardness of the hard-faced layer increased by 17.77% higher than its base substrate. Because of the hard precipitates and higher microhardness made by the weld thermal cycle, the hard-face layer showed maximum Co-efficient of Friction (CoF) of 0.540. Debris and grooves are found with the SEM examination of the wear specimens. Higher impedance offers better corrosion resistance to the hard-faced layer Inconel 718. The EDX analysis confirms the presence of Chromium, Molybdenum, and Niobium contents at the hard-faced layer. These elements silently support better corrosion resistance compared to the base substrate of Stainless steel 321. [ABSTRACT FROM AUTHOR]

Hardfacing is a widely used technique to create wear-resistant layer on the base material to ensure good durability and performance under harsh operating conditions. However, despite its effectiveness in improving wear resistance, hardfaced layers can sometimes exhibit softening phenomena during welding, compromising their mechanical properties and overall performance. In this research, the effect of heat input was investigated in case of Fe-based hardfacing material with high Cr content. 4 different heat inputs were applied with gas metal arc welding and significant differences were determined in hardnesses, which can be influential to the lifetime of hardfaced parts. Hardness drop happens in the heat-affected zones between the hardfaced layers and the highest heat input causing the most significant softening (20% hardness drop). [ABSTRACT FROM AUTHOR]

Stellite 6 is a Co-based alloy with excellent wear and corrosion resistance, resulting in it frequently being used as a hard-facing material. The main defect that occurs in the hard-facing process is the peeling of the hard-facing layer, which is caused by thermal stress due to differences in thermal expansion coefficients. This peeling phenomenon can be prevented by using a material with an intermediate coefficient of thermal expansion as a buffer layer. Component surfaces are strengthened through a technique called hard-facing, which increases the components' resistance to wear. In order to increase the wear and corrosion resistance of metal components, a high-hardness substance is usually coated onto their surface. Grinding is carried out to smooth the surface after the material is welded onto the base component. Small pieces, also referred to as "scrap", are frequently produced during this surface machining procedure. In the hard-facing process, scrap containing a mixture of base material and Stellite 6 is generated during material processing. If this scrap can be used as a buffer layer, the cost of raw materials can be reduced through the recycling of resources, and the overall energy consumption for recycling can be reduced because the process of separating Stellite 6 from the scrap is eliminated. In this study, the physical properties of Stellite 6 with Fe added were explored to determine whether the scrap produced could be used as a buffer layer. When iron was added to the mixture, the amount of carbide decreased, in addition to the wear resistance and hardness decreasing. Regarding the thermal expansion coefficient, the thermal expansion coefficient of Stellite 6 was found to be 15.879 μm/m·°C at 300 °C, and that of Stellite 6 with 40% Fe added was found to be 14.313 μm /m·°C at 300 °C. The thermal expansion coefficient of carbon steel is reported to be 12.8 μm /m·°C at 300 °C; thus, Stellite 6 with 40% Fe can be used as a buffer layer for Stellite 6 and carbon steel because of its suitable thermal expansion coefficient. [ABSTRACT FROM AUTHOR]

Stellite 6 is a Co-based alloy with excellent wear and corrosion resistance, resulting in it frequently being used as a hard-facing material. The main defect that occurs in the hard-facing process is the peeling of the hard-facing layer, which is caused by thermal stress due to differences in thermal expansion coefficients. This peeling phenomenon can be prevented by using a material with an intermediate coefficient of thermal expansion as a buffer layer. Component surfaces are strengthened through a technique called hard-facing, which increases the components’ resistance to wear. In order to increase the wear and corrosion resistance of metal components, a high-hardness substance is usually coated onto their surface. Grinding is carried out to smooth the surface after the material is welded onto the base component. Small pieces, also referred to as “scrap”, are frequently produced during this surface machining procedure. In the hard-facing process, scrap containing a mixture of base material and Stellite 6 is generated during material processing. If this scrap can be used as a buffer layer, the cost of raw materials can be reduced through the recycling of resources, and the overall energy consumption for recycling can be reduced because the process of separating Stellite 6 from the scrap is eliminated. In this study, the physical properties of Stellite 6 with Fe added were explored to determine whether the scrap produced could be used as a buffer layer. When iron was added to the mixture, the amount of carbide decreased, in addition to the wear resistance and hardness decreasing. Regarding the thermal expansion coefficient, the thermal expansion coefficient of Stellite 6 was found to be 15.879 μm/m·°C at 300 °C, and that of Stellite 6 with 40% Fe added was found to be 14.313 μm /m·°C at 300 °C. The thermal expansion coefficient of carbon steel is reported to be 12.8 μm /m·°C at 300 °C; thus, Stellite 6 with 40% Fe can be used as a buffer layer for Stellite 6 and carbon steel because of its suitable thermal expansion coefficient.

Hard-facing as a type of the coating depositing is increasingly used today. Physical-chemical-metallurgical characteristics of contact layers in tribo-mechanical systems depend on the operating conditions and the conditions under which the work surfaces were created. That is the reason the influence of the processing procedures and regime, used in the contact surfaces formation, on development of the wear process of contact elements, is being considered ever more. To determine the influence of the hard-facing technology on characteristics of the gears' working surfaces, the experimental investigations were performed on samples hard-faced on the steel for cementation, by varying the filler metals (FM) and the hard-facing regimes. The samples tested were hard-faced by five "hard" and three "soft" filler metals. Experimental investigations included measuring the hard-faced layers' hardness and determination of their microstructure, as well as the wear resistance in the laboratory conditions, on tribometer and on a specially designed device for tests in the real operating conditions of gears. The wear intensity was monitored by the wear trace's width in the laboratory conditions and by the share of the teeth surfaces affected by the destructive pitting in the operating conditions. The results obtained were compared to results of the base metal (BM) tests, which provided the certain conclusions on which filler metal and which welding procedure are the optimal ones for regeneration of the worn teeth surfaces. [ABSTRACT FROM AUTHOR]

During the process of regeneration of machine parts, certain phenomena occur that have a significant impact on the loss of their working ability. Hereditary properties are expressed by the interdependence of geometric and physical-mechanical-metallurgical parameters of gear teeth created during the technological operations of regeneration of worn teeth by hard-facing. The influence of the type of additional material (electrodes and their combinations) on the tribological characteristics of welded gear teeth was considered, whereby the so-called hard additional materials were applied. Those are the additional materials that give the required surface hardness of the teeth without subsequent thermal or thermochemical treatment. This research did not involve the regeneration of specific worn gears removed from machine systems, but the new gears were made, which were then damaged and then regenerated by hard-facing using the shielded metal arc welding (SMAW) procedure. Thus, all the tested gears were made of the same material, belonged to one batch and were machined on the same machines with the same machining regimes. The tests were performed on samples made of 20MnCr5 steel for cementation, on a tribometer by the “block on disc” method, which was designed to simulate the operating conditions of coupled teeth of concrete gears in the exploitation conditions. Based on the conducted tribological tests, the average coefficients of friction and topography of the surfaces were determined by measuring the wear trace and it was defined which additional materials give the best tribological characteristics of the surfaces of gears regenerated by hard-facing.

In this study, the metal inert gas (MIG) welding process is taken to deposit the Inconel 718 material on 321 stainless steel. Various modes like the DC, DC-pulsed, and DC-wave-pulsed modes in MIG welding are used for depositing Inconel 718. The primary parameters such as the welding current (90–120 A) and speed (150–350 mm/min) are varied within the range for making the layer deposition over 321 stainless steel. After performing the layer deposition, the dilution, contact angle, and peak temperature are analyzed to find the optimal MIG welding mode. From the macrograph, very low dilution (7.44%) is identified for the DC mode. The most inferior contact angle (θ) of 49° was measured for the DC-wave-pulsed mode. The simulation work predicted a peak temperature of 2800°C for the DC mode. Considerable microstructure changes have occurred at the weld deposition (dendritic structure) and HAZ (grain coarsening) for all the three modes. At the top, interface, and HAZ locations, the microhardness obtained from the DC-pulsed mode is in between those of the DC and DC-wave-pulsed modes. Overall, the DC-pulsed mode is qualified for making the metal deposition and further work. For 50% overlap, defect-free 2-mm-thick layer depositions are made on the 321 stainless steel surfaces. [ABSTRACT FROM AUTHOR]

Hard-facing process is widely used for improving the wear resistance of mild steel. During the application of hard-facing, due to high temperatures, residual stresses and deformations may occur. The tensile residual stresses may cause crack propagation on the hard-faced part. The purpose of this study is to utilise minimum computer work for minimizing these residual stresses and deformations during the hard-facing of mild steel. The fully coupled transient heat transfer and structural analysis was performed for calculations. The double-ellipsoidal moving heat source was utilised to simulate the heat input from the gas metal arc welding (GMAW). Only eight numerical simulations were performed to minimize the computer work; the grey relational analysis was used for minimizing both the residual stresses and deformations. Welding speed, welding current, and welding pattern were considered as changing parameters. At the end of the numerical and statistical solutions, it is observed that heat input should be kept minimum to minimize the stresses and deformations. But it is obvious that the heat input must provide a temperature greater than the melting point. Straight patterns always produce better results for minimizing stresses and deformations. Transverse stress at the beginning and end of the longitudinal path gets higher significantly after cooling. Cooling does not affect the total deformation.

In this study, the surface alloying process was carried out by using Plasma Transfer Arc (PTA) and Shielded Metal Arc Welding (SMAW) on the surfaces of plain carbon AISI 1030, 1040, 1050 steel materials. The performance of the coatings was evaluated by applying mechanical tests and electrochemical techniques. The results show that the resistance against the plastic deformation increased significantly by surface alloying; it reached the highest value of 896 HV with SMAW coating. The wear test findings exhibited that the surface alloying process improved the wear properties of the materials, and it was more pronounced for the coating powder Toolcord. In general, SiC+B4C coated steels hard-faced with the PTA method demonstrated better corrosion potential and corrosion rate compared to SMAW coatings. This improvement is probably due to the attendance of boron oxide in the oxide film, making it more resistant against Cl− attacks. The Nyquist analysis showed a semi-circle capacitive loop at high frequency and an inductive loop at low frequency for all samples. The electrochemical impedance spectroscopy analysis showed that better corrosion resistance was observed for 1030 when using PTA with powder SiC+B4C, while for 1040 and 1050, it was SMAW with powder Citodur. [ABSTRACT FROM AUTHOR]

The gas tungsten arc welding (GTAW) process is an excellent way of performing quality hard- -facing applications. The residual stresses and distortions are encountered in hard-facing. There are several methods to decrease residual stresses. Changing the welding pattern, changing thickness and preheating can be mentioned for this purpose. In this work, the influence of the welding pattern, plate thickness and preheating was investigated. The temperature distribution with the same welding conditions was used for validation of the numerical model. The total deformation in a 2mm plate was 15 times higher than in a 6mm plate with the same welding conditions. [ABSTRACT FROM AUTHOR]

Hard-facing process is widely used for improving the wear resistance of mild steel. During the application of hard-facing, due to high temperatures, residual stresses and deformations may occur. The tensile residual stresses may cause crack propagation on the hard-faced part. The purpose of this study is to utilise minimum computer work for minimizing these residual stresses and deformations during the hard-facing of mild steel. The fully coupled transient heat transfer and structural analysis was performed for calculations. The double-ellipsoidal moving heat source was utilised to simulate the heat input from the gas metal arc welding (GMAW). Only eight numerical simulations were performed to minimize the computer work; the grey relational analysis was used for minimizing both the residual stresses and deformations. Welding speed, welding current, and welding pattern were considered as changing parameters. At the end of the numerical and statistical solutions, it is observed that heat input should be kept minimum to minimize the stresses and deformations. But it is obvious that the heat input must provide a temperature greater than the melting point. Straight patterns always produce better results for minimizing stresses and deformations. Transverse stress at the beginning and end of the longitudinal path gets higher significantly after cooling. Cooling does not affect the total deformation. [ABSTRACT FROM AUTHOR]

• Hard-facing performed by CMT using a sinewave weaving technique with a 30% overlap. • Laves phase formation is suppressed by the weaving method with overlapping. • Hardness and impact properties are improved by fine grains & strengthening elements. • Energy dissipation aided by intermetallics and secondary phases in the overlay layer. • The high positive corrosion potential (Ecorr) enhances the corrosion resistance. Cold Metal Transfer process is used to hard-face the Inconel 718 alloy onto the Stainless Steel 304 material. The optimized parameters from the Bead on Plate trials were determined as a wire feed rate of 7 m/min, deposition speed of 15 cm/min, welding current, and voltage of 175 A and 14.9 V, respectively. Hard-facing is carried out with the sinewave weaving technique along 30 % of overlapping beads. The analysis is focused on revealing the hard-faced specimens' microstructural, mechanical, and electrochemical corrosion properties. The hard-face layer exhibits grains of mixed modes, including columnar, cellular, and fine equiaxed grains. The increased heat transfer disintegrates grain formation and reduces secondary arm spacing development. SEM-Elemental mapping shows the reduction of Niobium (3.61 %) segregation and laves formation. The overlay layer has a maximum hardness of 343.1 HV 0.5 over the base substrate with 204 HV 0.5. The impact test reveals the hard-faced layer absorbs more energy (26.3 %) than the substrate. Dynamic Mechanical Analysis results indicate overlay layer enhancing damping properties. The electrochemical corrosion test findings suggest that the hard-faced layer's high corrosion potential (Ecorr = 8.533 mV) corresponds to a high corrosion resistance. Phase and intermetallic formations, distribution of elements, fractured and corrosive surface morphologies are analyzed using SEM, EDX, and elemental mapping results. [ABSTRACT FROM AUTHOR]

In this study, experiments with various parameters were performed to apply laser cladding to the exhaust valve face of a marine engine and optimum conditions were derived. The used specimen was an actual exhaust valve, and the heat source was a high-power diode laser. Cladding was applied to the exhaust valve face using the optimum conditions, and a sound clad layer without internal defects, such as pores and cracks, was formed. The average hardness of the clad layer formed under the optimum conditions was higher than 529 Hv. Component analysis showed a very low dilution rate inside the clad layer. [ABSTRACT FROM AUTHOR]

This paper points out complex working conditions of forging dies, which are the most frequent causes of their damage, and proposes suitable hard-facing repair procedures. The shear strength between the hard-faced layer and base metal has been measured using specially developed tool, and correlation between output results and the applied hard-facing technology is established.

Degradation of materials due to the impact of solid particle is a major material wastage process. Modifying the surface of materials can be considered to be a potential method of improving the resistance to erosion. In the present days, weld hard-facing is a popular surface modification process. Engineering industries are opting for hard-facing because of its low capital cost, low operational cost, and operational simplicity. In the context of erosion-resistant hard materials, a series of Co-based alloys that can be deposited by hard-facing is one of the most suitable materials. The present analysis has been carried out to evaluate the influence of processing conditions of hard-faced Co-based alloyed layer on solid particle erosion response at ambient temperature. These layers were deposited on mild steel substrate by weld hard-facing. The mechanical properties and microstructural features of these coatings were evaluated by means of X-ray diffraction technique, optical microscopy, scanning electron microscopy, and microhardness tester. Erosion rate was measured using an air jet erosion test rig. The eroded surface morphology and the transverse section of eroded surfaces were viewed using scanning electron microscopy. The results showed that hard-facing improves erosion resistance of the substrate. The erosion responses of most of the coatings were ductile. Material loss from hard-faced coating was by formation of lips followed by their fracture which initiated in the interdendritic regions. [ABSTRACT FROM AUTHOR]

The surface of tamping machıne's digger is covered with a filler material because it is a material that is continuously used in TCDD (The State Railways of the Turkish Republic) lines and it is a material that needs to be constantly changed because it is exposed to abrasion. For many years, this process with the same method and same electrodes. In our work, we aimed to produce a variety of welding electrodes with a more efficient, longer-lasting and less labor-intensive method for production tamping machine’s digger. Considering factors such as applicability, easy availability, cost, welding method and hard facing welding electrodes to be used in our work have been determined. The necessary materials were then provided. The diggers of tamping machines were welded with 5 different welding electrodes. Then, the effect of each of these electrodes on the mechanical properties and strength was compared. Used tamping machine’s diggers processing was carried out with different hardfacing welding electrodes. Mechanical properties and strength effects of different welding electrodes was analyzed. [ABSTRACT FROM AUTHOR]

The microgrinding experiment of Zr-based bulk metallic glasses (Zr-based BMGs) is conducted by using a JX-1A ultra-precision grinding lathe. The simulation on grinding temperature for Zr-based BMG, the hardness of the grinding surface for Zr-based BMG, the morphology of grinding surface, the metamorphic layer, the morphology of grinding chips, and the wear of microgrinding wheels are investigated. The microcracks on the surface of Zr-based BMGs are observed and investigated, and the causes of microcracks on grinding surface are analyzed. The metamorphic layer of Zr-based BMG is also investigated. It is found that the thickness of the metamorphic layer produced by microgrinding wheel with cubic boron nitride (cBN) abrasives is less than the thickness of the metamorphic layer produced by microgrinding wheel with diamond abrasive, and the causes of metamorphic layer of Zr-based BMGs caused by microgrinding are analyzed. The microchip morphology of Zr-based BMGs is also observed and studied. The causes of the microchips and the removal mechanism of Zr-based BMG are analyzed. Finally, the wear of microgrinding wheels is observed and analyzed. This study concludes that the microgrinding wheel with cBN abrasive is more favorable for microgrinding for Zr-based BMGs. [ABSTRACT FROM AUTHOR]

The influence of alloying (10 wt% Molybdenum) and post deposition treatment (Laser Surface Melting) on the structural characteristics and wear performance of Plasma Transfer Arc deposited M2 hardfacings have been investigated. The nature of matrix and carbides of M2 hardfacing had changed upon Molybdenum addition while the Laser Surface Melting caused structural refinement and a decrease in carbide volume fraction. Despite an increase in hardness, Laser Surface Melting has resulted in reduction in sliding wear resistance against alumina counterface, while the Molybdenum enhanced the wear resistance even with decrease in hardness. This counter intuitive behaviour is attributed to Magnelli oxide containing tribo-oxide layer formation on the worn surface of Molybdenum alloyed hardfacings. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the abrasive wear loss as well as the wear mechanisms of hardfacing layers with and without tungsten carbides (WC) included in the matrix in different friction wheel test (FWT) configurations. The FWT setup is varied in regard to the materials of the rotating wheels, whereat steel and rubber materials are utilized to achieve varying wear mechanisms as representative conditions for stone milling as well as low density wood cutting processes. Coatings including fine particles of WC highlight the highest resistance against abrasive wear in rubber wheel testing condition, at which microcutting acts as the dominant effect. In comparison to the hardfacings without WC, the mean material loss majorly decreases by about 75%. On the contrary, the mean material loss of fine WC reinforced coatings increases up to 93% compared to the condition without WC if a steel wheel is utilized as rotating counterpart. Thereby, the coatings with comparably coarse WC reveal the minimum material loss with a decrease over 70% compared to the condition without WC. In conclusion, the inclusion of WC in hardfacing coatings significantly increases the wear resistance. The experimental wear test results highlight the fact that in order to achieve the optimal wear resistance the material characteristics of the hardfacings need to be properly defined considering the predominant wear mechanisms under in-service conditions. [ABSTRACT FROM AUTHOR]

Wear resistance and fracture resistance are the main indicators of the quality of hard alloys. The risk of fracture of such materials is usually difficult to assess due to high hardness. However, this can be done by measuring the morphology of microstructure. The structure of hard alloys is diverse. Hardening particles (carbides, borides, particle clusters, dendrites, etc.) are located in the matrix. They have different geometries, the thickness of matrix interlayers varying. This assumes using a statistical approach to the analysis of structures. The statistical nature of structural elements is established with digital optical microscopy. Objective methods for the binarization and filtration of structure images are proposed. It is shown that the average thickness of the interlayers and the asymmetry of the thickness distribution can be used as an effective assessment of the risk of fracture of hard alloys. The prediction of the risk of fracture is validated by comparing the morphology of structures and fractures of hard alloys. [ABSTRACT FROM AUTHOR]

This study used the cold metal transfer (CMT) process to deposit Inconel 718 (IN718) as a hard-facing layer on the Base Substrate (BS) of 304 stainless steel (SS304). Different profiles like straight/stringer and sinewave weaving techniques are adopted to deposit the hard-faced layers. For the above profile, IN718 is deposited as a single-track and 30 % overlap to study the impact of heat input on the base substrate. Through the Bead on Plate (BoP) trials, optimal parameters of welding current (175 A), speed (15 cm/min), and wire feed rate (7 m/min) is identified. Sinewave beads (single track) explored a minimum dilution of 13.46 % compared to all the combinations. The sinewave distributed the heat uniformly compared to the straight/stringer profile. At the top surface, fine grains with an equiaxed structure are identified. Annealed twins are present at the base substrate, and elongated columnar grains near the interface are identified through EBSD. The sinewave with 30 % overlapped layers exhibited a maximum hardness of 274.4 HV 0.5 at the Hard Face Zone (HFZ), whereas the base substrate hardness was 204 HV 0.5. Further, the hard-faced samples achieve an ultimate strength of 750 Mpa through the tensile test. The micro-voids, dimples, and riverine structure observed from fractured surfaces witnessed the ductile fracture. The segregation of Niobium is scattered at the inter-dendritic region. The SEM-EDX results confirm the existence of Niobium, Nickel, and Molybdenum elements. • The sinewave technique & the lower heat input of CMT produced less dilution. • The faster cooling rate reduces the secondary arm spacing in dendrites. • An increase in LABGs fraction opposes dislocation moments & refines its walls. • Stirring action increases the concentration of Mo and Nb in interdendritic regions. • Sinewave (30 % overlap) layers show maximum hardness and ultimate strength. [ABSTRACT FROM AUTHOR]

Research in the field of hard-facing of various parts mechanical systems' are being done for technical and techno-economic reasons. The reasons for introducing the new reparation technologies by hard-facing are numerous: three quarters of all the mechanical parts of engineering could be regenerated or manufactured by hard facing; the working life of the repaired part reaches or even exceeds the working life of a new part, while the working life of the hard faced manufactured part surpasses several times the working life of the new part manufactured by some other technology. Large number of damaged and, frequently even broken parts, cause terminations of the working process. Thus, due to difficulties in procurement of new, mainly imported parts, the alternative solution must be applied. It is sown that the a proper choice of the hard-facing technology is related to the complex procedure of checking the quality of the hard faced layer, what indicates that the reparatory operations could be performed only in specialized regeneration workshops, which are furnished with adequate equipment and corresponding expert and skilled staff. The estimated net benefit for the analyzed parts is exceptionally high, regardless of the fact that the additional external and internal effects have not been quantified.

The paper concerns the study of mechanical and tribological characteristics of hardfaced layers of dispersive reinforced material in pure aluminium metal matrix. The wear resistant coatings were deposited by shielded gas metal-arc welding applying either metal inert gas (MIG) or tungsten inert gas (TIG), with standard wire filler onto the buffer layer -- a baked resistant film containing metalised and flux coated micro/nano SiC particles. The hardfaced layers were studied by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray microanalysis (EDX). Nanoindentation and wear resistance tests were carried out. [ABSTRACT FROM AUTHOR]

The paper focuses on the corrosion behavior of high velocity oxygen fuel (HVOF) sprayed WC-17Co, WC-10Co-4Cr, Cr 3 C 2 -25NiCr coatings in alkaline-sulfide solution (S 2− , 0.2 ml/L, pH = 10). Eighteen days of immersion test is carried out and corrosion rate analysis shows that the Cr 3 C 2 -NiCr coating of low porosity exhibits the best corrosion resistance. In alkaline-sulfide solutions, porosity, passive film and microgalvanic between hard phase and binder phase have significant effect on the corrosion behavior of coatings. The corrosion mainly occurs in binder phase from SEM, though WO 3 , WS 2 , Cr 2 S 3 are detected in XPS. In WC-17Co coating, the binder phase Co transforms to Co oxides and serious corrosion can be observed in binder phase. WC-10Co-4Cr coatings suffer localized corrosion since galvanic corrosion occurs between locations with different solubilities of W in Co binder. Cr 3 C 2 -25NiCr coating shows slight corrosion with the formation of NiS/Ni2O3/Cr2O3from the binder and Cr 2 S 3 from the hard phase. The results are verified by the polarization curves, which show the longest passive region and lowest I corrosion of Cr 3 C 2 -25NiCr coating. [ABSTRACT FROM AUTHOR]

The paper presents the capabilities of welding techniques to creating properties of wear resistant high chromium cast iron alloy. The use of the right kind of welding sequence allows you to change the structure and properties of the obtained welds. Tests were conducted for one type of additive material in the form of self shielded core wire. In order to determine the effect of the type of welding sequence on the properties of welds performed welding using string bead and weave bead. The resulting weld was tested on hardness and research structure in an optical microscope. In the following studies have been made erosive tests wear of made hardfacing. String beads gave structure rich in carbides and harder about 270 HV of the weld with weave bead. Also, wear resistance was nearly twice as better for welds made with string beads. In the experiment a decisive role in the resistance to wear plays a high hardness of the deposit and the presence of carbides in its structure. Changes in the basic parameters of the deposition process allows for the formation of structure and properties of hardfacing welds in a wide range. [ABSTRACT FROM AUTHOR]

In arc surfacing over the layer of alloying charge, the conditions for producing layers with varying composition and structure in the zones of separate beads were determined. On the deposited surface the carbon-containing fibres were preliminarily deposited in bands, the width and distance between which were selected from the conditions of positioning the end of the electrode with displacement relative to the edge of the bands. To fix the fibres, a primer was used, into which the iron powder and aerosol SiO2 were added. During the experiments a number of deposited layers, the eccentricity in the arrangement of bands relative to the axis of electrode wire, as well as the induction of external magnetic field were varied. The difference in hardness of the metal across the width of the deposited beads (up to HRC 9–12) and the successively deposited layers (up to HRC 15–25) was established. The hardness reaches its maximum values at the eccentricity c = 4 mm and induction B = 40–80 mT and also at c = 10–12 mm and B up to 40 mT. The increase in hardness is observed with increase in the amount of deposited layers. The metallographic analysis recorded an increase in the fraction of hardening structures (in the form of acicular bainite and martensite) from 15–22 to 25–35 % in the second layer and more than 50 % in the third one 13 Ref., 1 Table, 10 Figures. [ABSTRACT FROM AUTHOR]

A modeling procedure is proposed based on established features of the effect of adding modifiers and process parameters simulating surfacing on the solidification front structure and intensity of primary phase equiaxed crystallite front nucleation and growth kinetics within the volume of melt. [ABSTRACT FROM AUTHOR]

Development of technology for restoring worn hydraulic cylinders by plasma-powder surfacing providing new operating properties is of current interest. The possibility is studied of restoring rods by surfacing with a coating of the Fe-C-Cr-V system. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study is to show which filler metal is the best for hard facing. Because the quality of the surface layer has a great influence on the working life of parts, the purpose was to extend the working life of parts exposed to intensive wear. The tested hard-faced models were made of low carbon steel to save the expensive base metal and to analyze the possibilities of extending the service life of existing structural parts.Design/methodology/approach Samples were prepared from plates hard faced with various filler metals. Samples were then subjected to experimental testing – testing of tribological properties and hardness and microstructure. Testing was done in conditions similar to real ones – with a sliding speed of 0.25, 0.5 and 1 m/s and with a load of 50, 75 and 100 N and in most rigorous dry conditions. Research was done by using a combination of experimental and theoretical approaches.Findings The paper shows the results of the experimental testing of four different filler metals aimed for hard facing of parts exposed to highly intensive wear. Results shown that CrWC 600 alloy is the most favorable filler metal for hard facing of parts such as those of construction mechanization and those subjected to intensive abrasive wear at stone mines.Practical implications All obtained results are real and fully applicable, as there is a huge industrial need for these types of technologies. With the application of these technologies, beside money savings, the working life of parts can be significantly extended.Originality/value The research presented in this paper was conducted because of the lack of results from this area in Serbia and because of the necessity for application of obtained results in companies for road maintenance and stone excavation in the region of Šumadija, Serbia. [ABSTRACT FROM AUTHOR]

The procedure for experimental determination of the longitudinal and lateral residual stresses in the multi-layer hard-faced plates, made of the hot work tool steel used for forging dies manufacturing, is presented in this paper. The objective of this research was to establish the influence of the multi-layer hard-facing on residual stresses in the thin and thick plates, which could later, in exploitation, cause the appearance of cracks and fracture. The influence of tempering on decreasing the residual stresses was monitored, as well. The plates were hard-faced in three layers, while the stresses were measured by the magnetic method. The obtained results have shown, among others, that the residual stresses are higher in the thick plates, as well as that the proper regime of the heat treatment can significantly reduce the level of residual stresses. [ABSTRACT FROM AUTHOR]

The drilling process requires the transportation of the drilling fluid (mud) loaded with high abrasive materials like sand and rock cuttings. The drilling mud is transported through the close running clearance of the valve opening at high flow velocities, producing high abrasive wear within a short period of time. As the drilling process makes it impossible to operate the pump at lower speed in order to reduce the flow velocity through the valves, the valve protection against abrasive wear can be realized by the following actions: – designing the valve to control the flow stream, avoiding abrupt changes in flow direction, close clearances and turbulent flow; – using abrasive wear resisting materials by applying hardfacing technologies, such as case hardening, cladding by weld overlays and coating by thermal spray techniques. This article is based on a comparative investigation of these methods for protection of the valve seat's working surface, operating under abrasive wear conditions. The comparison is based on the analysis of microstructure and hardness obtained by applying different hardfacing technologies. [ABSTRACT FROM AUTHOR]

This articles examines the formation of high-quality joints between aluminum bronzes and copper-nickel alloys that contain different amounts of nickel. The joints are formed by explosion welding or hard-facing as part of the fabrication of products for chemicals production, gas engineering, shipbuilding, and other sectors of industry (reinforcement bars, heat exchangers, pipelines, etc.). A study is made of the effect of the nickel content of copper-nickel welding wires on crack formation in hard-faced metal, its structure, and its mechanical properties when aluminum-nickel bronze of grade Br.A9Zh4N4Mts1 is joined with copper-nickel alloys by argon-arc welding and hard facing. It is shown that the use of welding wires made of copper-nickel alloys with a nickel content of up to 18% guarantees the formation of high-quality crack-free joints with mechanical properties that are comparable to the properties of the lower-strength material which is used. [ABSTRACT FROM AUTHOR]

The effect of five different buffer layers followed by a hard facing electrode deposited on gray cast iron plate (ASTM grade 2500) upon performance of interface between substrate cast iron and deposited layers as well as abrasive wear behaviour of hard faced deposits were studied. The results show that high nickel buffer electrode attributed best performance of interface bond in terms of shear strength and relatively lower nickel buffer electrode attributed best abrasive wear properties. The shear strength at the interfaces and wear properties has been correlated with microstructure and micro-mechanism of fracture in shear strain and micro-mechanism of metal removal in abrasive wear. [ABSTRACT FROM AUTHOR]

A rotary tiller is a mechanized agricultural implement popularly used to save time, human effort and fuel in preparation of soil bed. However, under complex abrasive environments, tiller blades are subjected to extreme surface wear, particularly in dry sand, which considerably affects its service life. The aim of this study was to improve the service life of the tiller blade in order to cut the idle time required to replace the blade periodically during cultivation. The aim was carried out by means of hardfacing, where the effect of the hard facings on the extent of wear and the wear characteristics of the tiller blades were examined. The influence of Cr is studied by hard facing of leading edge of tiller blades made of high tensile steel by gas tungsten arc welding using four different electrodes. The comparison of hard faced blades with un-hard faced (standard) blade was made through field and laboratory test. A field test was conducted on a 50 acre area of rice field after combine harvesting. During field test, rice stubbles were present and the condition of soil was dry and sandy. Different positions were selected for the test blades in the tiller to collect the meaningful data. The average wear rate of the un-hard faced blade was found as 7.08 gm/acre, while those of 5HCr, 7.5HCr, 12HCr and 8HCr hard facings were 5.02, 4.3 2.84 and 4.22 gm/acre respectively as indicated by field test results. A significant improvement was observed in the wear protection provided by hard facings over the un-hard faced blade. [ABSTRACT FROM AUTHOR]

Research in the field of hard-facing of various parts mechanical systems' are being done for technical and techno-economic reasons. The reasons for introducing the new reparation technologies by hard-facing are numerous: three quarters of all the mechanical parts of engineering could be regenerated or manufactured by hard facing; the working life of the repaired part reaches or even exceeds the working life of a new part, while the working life of the hard faced manufactured part surpasses several times the working life of the new part manufactured by some other technology. Large number of damaged and, frequently even broken parts, cause terminations of the working process. Thus, due to difficulties in procurement of new, mainly imported parts, the alternative solution must be applied. It is sown that the a proper choice of the hard-facing technology is related to the complex procedure of checking the quality of the hard faced layer, what indicates that the reparatory operations could be performed only in specialized regeneration workshops, which are furnished with adequate equipment and corresponding expert and skilled staff. The estimated net benefit for the analyzed parts is exceptionally high, regardless of the fact that the additional external and internal effects have not been quantified. [ABSTRACT FROM AUTHOR]

Wear is major life limiting factor of the glass processing tools. A complex interaction of hot viscous glass and oxide layers at tool surface, damages tool by cyclic contact. Hardfacing is one of the most useful and economical ways to improve the performance of components submitted to severe wear conditions. The specific wear behavior of a hardfacing coating depends on its chemical composition, the microstructure obtained after hardfacing process, and finally the harfacing technology used to apply them. The main objective of this study was to evaluate wear behavior for coatings applied by various hardfacing techniques consist of gas tungsten arc (TIG) welding, plasma transferred arc (PTA) welding, and chromizing. Two different commercial cobalt based hardfacing electrodes (Stellite 12 and Tribaloy T-401) were employed to investigate the effect of the hardfacing alloys. In order to simulate real field conditions on a lab scale, tests were performed with a specially designed system and actual process parameters. The qualitative evaluation of wear behavior was supported by microstructural investigations using optical microscopy and scanning electron microscopy (SEM + EDS). The quantitative investigations were performed using profilometry and hardness tests. The results showed the superiority of PTA welding in comparison with other hardfacing techniques. The best wear resistance was obtained in PTA welding hardfacing with Stellite 12 alloy. [ABSTRACT FROM AUTHOR]

Abstract: The harden-surface-welding (hardfacing) alloys with different La2O3 additives were developed. The microstructure was observed and the phase structure was determined. Meanwhile, the hardness and wear resistance were measured, respectively. Moreover, the tensile strength, yield strength and impact toughness were measured too. In addition, the fractograph of the hardfacing alloy was observed. On this basis, the LaO-doped C terminated interface was taken, in which, the interfacial energy of LaAlO3 (100)/austenite (100) interface was calculated and the effectiveness of the LaAlO3 as the heterogeneous nucleus of austenite was analyzed by first-principles calculations. The experimental results indicate that, with the increase of the La2O3 additive, the primary austenite grain dimension of the hardfacing alloy decreases obviously. Meanwhile, the hardness, strength, toughness and wear resistance of the hardfacing alloy increase simultaneously. When the La2O3 additive is 3.32wt%, all of the mechanical properties are the largest, the hardness is HRC 50, the tensile strength and yield strength are 1502MPa and 1334MPa respectively, the impact toughness is 7.1J/cm2 and the wear resistance is 1.29mg/min. The calculated results show that, for the LaAlO3 (100)/austenite (100) interface with LaO-doped C terminated structure, the interfacial energy is high when the La chemical potential Δμ La and C chemical potential Δμ C are low. However, with the increase of the Δμ La and Δμ C , the interfacial energy decreases gradually. When the Δμ La and Δμ C meet the condition of −3.792eV≤0.543Δμ La +0.311Δμ C ≤−3.588eV, the interfacial energy of LaAlO3 (100)/austenite (100) interface is in the range of 0–0.204J, which meets the requirements of the heterogeneous nucleation interfacial energy. Therefore, LaAlO3 can be the heterogeneous nucleus of austenite. [Copyright &y& Elsevier]

Stainless steel of type AISI 316LN – one of the structural materials of fast neutron reactors – must have a long service life under conditions that subject it to different types of wear (galling, adhesion, fretting, and abrasion). Cobalt-based hard facings are generally avoided due to induced radioactivity. Nickel-based hard facings are strongly preferred instead. One alternative to both types of coatings is a hard-alloy coating of CrN. This article examines wear and friction characteristics during the sliding of uncoated steel SS316LN and the same steel with a CrN coating. In addition, a specially designed pin-on-disk tribometer is used to perform tests in a vacuum at temperatures of up to 1000°C in order to study the effect of oxygen on the wear of these materials. The morphology of the wear surface and the structure of the subsurface were studied by scanning electron microscopy. The formation of an adhesion layer and the self-welding of mating parts are seen to take place in the microstructure at temperatures above 500°C. It is also found that steel SS316LN undergoes shear strain during sliding wear. The friction coefficient depends on the oxygen content, load, and temperature, while the wear rate depends on the strain-hardening of the surface of the material being tested. [ABSTRACT FROM AUTHOR]

Results obtained at the Mariupol Metallurgical Combine with a new technology for reconditioning the steel work rolls of hot-rolling mills are presented. The technology is based on hard-facing of the rolls with strip electrodes made of steels 20Kh4MFB, 15kp, and 08kp. Rolls hard-faced with a composite consisting of alternating strong and ductile layers are shown to have good fracture toughness. The service life of the rolls is increased, their wear is made more uniform, and the amount of metal removed in regrindings is reduced thanks to differentiation of the composition and properties of the metal along the body of the rolls. Reconditioning rolls with the hard-facing materials made by the Mariupol combine increases productivity per 1 mm of roll wear and makes the reconditioning operation more profitable. [ABSTRACT FROM AUTHOR]

Weld overlay is one of the most critical welding processes for pressure vessels, reactors, valves and pipelines construction. Welding parameters control, influencing mechanical properties of weld metals, is obtained - as well as other welding processes - through the use of welding procedure specification (WPS), necessary to provide a welding operations plan. Production of welding procedure specification is a basic factor, but it is not enough to ensure welded joints requirements. Some defects and chemical compositions of clad metals can be evaluated by nondestructive methods while it is not possible to check metallurgical imperfections with non-destructive methods. These factors require a proper quality control, before and during overlay welding, essential for qualification of welding procedures. [ABSTRACT FROM AUTHOR]

Here is analyzed selection of the optimal technology for heat treatment during the reparation of the damaged forging dies. Those tools are manufactured from alloyed tool steels for operation at elevated temperatures. Those steels are prone to self-hardening, so in reparatory hard-facing they must be preheated, additionally heated and tempered. During the tempering, in temperature interval 500-600°C, a secondary increase of hardness and decrease of impact toughness occurs, the so-called reversible tempering brittleness. Here is shown that it can be avoided by application of metallurgical and technological measures. Metallurgical measures assume adequate selection of steels. Since the considered steels are per se prone to tempering brittleness, we conducted experimental investigations to define the technological measures to avoid it. Tests on models were conducted: tempering from different temperatures, slow heating and cooling in still air. Hardness measurements showed that at 520°C, the secondary increase of hardness occurs, with drop of the impact toughness. Additional hard-facing tests included samples tempered at various regimes. Samples were prepared for mechanical and metallographic investigations. Results presented illustrate influence of additional heat treatment on structure, hardness and mechanical properties of the hard-faced layers. This enabled establishing the possibility of avoiding the tempering brittleness through technological measures. [ABSTRACT FROM AUTHOR]