Cladding Method Research Articles

Effect of the Method of Formation of Composite Ti–TiC Coatings on Their Composition, Microstructure, and Strength Properties

In the present work, the results of study of the composition, microstructure, and strength properties of composite coatings based on titanium and titanium carbide obtained using two different surface treatment methods—electric arc method in an electrolyte and laser method—are presented. It is shown that the coating parameters affecting the strength properties of samples, such as the morphology and size of carbide grains in the coating composition along with the coating thickness, are significantly easier to adjust using the laser cladding method.

Laser cladding process of Fe/WC metal matrix composite coatings on low carbon steel using Yb: YAG disk laser

The paper presents the studies of selected properties of Fe/WC metal matrix composite coatings produced using different laser beam power values and different powder feeding rates. Coatings were produced using the Yb: YAG disk laser by laser cladding method. Laser beam powers equal to 600 W, 700 W and 800 W were used. Scanning speed of laser beam was the same for all the coatings and was equal to 600 mm/min. Laser beam spot diameter was 1.64 mm. Two powder feeding rates (6.25 g/min and 12.50 g/min) were applied. In this study macroscopic observation, microstructure and microhardness examination as well as XRD and EDS analysis were carried out. Corrosion resistance was also investigated. In Fe/WC coating produced using slower powder feeding rate dendritic carbides that nucleated on the primary tungsten carbide particles were observed. In the coatings produced using an increased powder feeding rate, a changed type of secondary carbide was observed, which was bar-shaped or plate-shaped. The results of the XRD and EDS analysis of the composite Fe/WC coatings showed the presence of WC, W2C phases as well as M23C6 and (Fe,W)3C complex phases. The mechanism of formation and growth of composite coatings was described on the basis of microstructures obtained. The highest microhardness and corrosion resistance were observed for coatings produced at a powder feeding rate of 12.50 g/min.

Printing special surface components for THz 2D and 3D imaging

The paper reports an off-axis large focal depth THz imaging system which consists of three 3D printed special surface components (two aspherical mirrors and an axicon). Firstly, the optical design software is used to design and optimize the aspherical parabolic mirror. Secondly, the optimized mirror is prepared by a 3D printing and metal cladding method. Thirdly, a THz axicon is designed for generation of quasi-Bessel Beam and a new geometric theoretical model of oblique incident light for axicon is established. Finally, the imaging system based on the special surface components is constructed. Its maximum diffraction-free distance is about 60 mm, which is 6 times higher than the traditional system. To verify the effectiveness, THz two-dimensional imaging experiments and three-dimensional computed tomography experiment are carried out. The results are consistent with the design and calculations.

Aluminium composites prepared by laser cladding assisted by friction stir processing

A laser cladding and friction stir processing hybrid method was employed to produce an Al matrix composite layer. The microstructure, phase composition, microhardness and conductivity of the composites were investigated. A laser cladding layer with a thickness of approximately 200 μm was prepared on a 1060 aluminium plate and it was broken up and distributed on the Al matrix after friction stir processing. The particle/Al interfaces exhibited extremely good interfacial integrity. Microstructural observations revealed that an obvious in situ reaction occurred at the particle/Al interfaces, which effectively improved the bonding between the reinforcement phase and the matrix. TEM analysis and selected area diffraction enabled the identification of the intermetallic compounds and confirmed them to be Al5Fe2 and Al3Fe. The average microhardness values of the friction stir processed composites reached approximately 85 HV. The electrical resistivity of the friction stir processed composites is slightly higher than that of the aluminium matrix.

Mechanical Investigations of ASTM A36 Welded Steels with Stainless Steel Cladding

The in-service life of ASTM A36 welded steel pipes in power plants is often shortened by ash corrosion. During the heating condition, the ash deposition on the welded steel pipes gradually reduces the thickness of the pipes, thus, reducing the lifetime. Instead of replacing the pipes with new ones, the cost could be significantly reduced if the lifetime could be further extended. Weld cladding was the method selected in this study to temporarily extend the service life of welded pipes. This paper performed the mechanical investigations of A36—A36 welded steel plates after coating the surfaces with 309L stainless steel with a cladding method. The residual stress was also tested to observe the internal stresses developed during the welding processes of A36—A36 specimens. The comparison between the coated and non-coated surfaces of welded steels was performed by using the tensile tests (at room and elevated temperatures), corrosion (pitting corrosion, intergranular corrosion, and weight-loss corrosion) tests, and wear (shot blasting) tests. The life-extension of both coatings was evaluated based on the tensile tests and the corrosion and wear tests provided the qualitative evaluations of the coating performance. The results showed that surfaces coated by cladding could be used to temporarily extend the life of ASTM A36 welded steel under the studied conditions.

Geometrical assessment and mechanical characterization of single-line Inconel 825 layer fabricated on AISI 304 steel by TIG cladding method

In the course of the deposition of Inconel 825 layer on AISI304 stainless steel by tungsten inert gas (TIG) cladding route, the geometry of the single line clad tracks for different processing conditions was evaluated and correlated with the employed processing current and pre-placed powder thickness. The analysis revealed an enhancement in the clad track width, clad height along with the dilution ratio, and the clad angle for increasing the TIG current. Nevertheless, no specific effect of pre-placed powder thickness was recorded. A detailed EDS analysis at the interface of the clad layer revealed an enhancement in the dilution of Inconel 825 with the substrate material in the clad zone and vice-versa in the substrate region for increasing the processing current. The micro-hardness value recorded at the cross-section of the clad track shows a consistent improvement (300–350 HV) as compared to the substrate material (220 HV). The sliding wear test of the samples extracted from the clad tracks performed against harden-die steel plate shows almost negligible height loss (6 µm) as compared to the uncoated steel specimen (125 µm) under similar test condition.

Strengthening mechanism in two-phase FeCoCrNiMnAl high entropy alloy coating

The two-phase FeCoCrNiMnAl high entropy alloy cladding layer was produced by laser cladding method, and its strengthening mechanism was studied. Using XRD, EDS, TEM and EBSD analyses, the phase and microstructural evolutions, dislocation density and distribution, and degree of lattice distortion were investigated. Nano-indentation and tensile tests were employed to study the hardness and tensile properties of the cladding layer, respectively. The results show that Al element, due to its large atomic radius, promoted the formation of BCC solid solution in the cladding layer and significantly refined the grains. Diffraction peak shift, change lattice constant change, interplanar spacing and crystal plane included angle calculations indicate that all the phases in the FeCoCrNiMn and FeCoCrNiMnAl cladding layers experienced serious lattice distortions. Dislocations in the FeCoCrNiMnAl coating mainly accumulated and moved in the softer FCC phase, increasing the material's resistance to plastic deformation. The combined effects of grain size, lattice distortion, dislocation density and dual-phase interaction significantly increased the plastic deformation resistance (i.e., tensile strength, yield strength and microhardness) of the FeCoCrNiMnAl coating compared to the FeCoCrNiMn coating, but also reduced the elastoplasticity.

Microstructure evolution of roll core during the preparation of composite roll by electroslag remelting cladding technology

AbstractIn the present study, the comprehensive analyses based on the numerical simulation, in situ observation, and metallographic detection were carried out for the roll core of GCr15/45 carbon steel composite roll manufactured by the new electroslag remelting cladding (ESRC) method. During the ESRC process, the temperature distributions at the different radial and longitudinal positions of the roll core have great changes due to the different degrees of heat conduction from the slag bath, as a result, various microstructure and properties were obtained at the different positions of the roll core. The results illustrated that the ESRC process tended to be stable as the composite height reached a certain value and the high-temperature austenitization process mainly occurred in the radial regions where R > 60 mm, whereas no significant changes occurred at the areas where R ≦ 60 mm. The coarse grains and few Widmanstatten structures with proeutectoid ferrite were generated in the roll core areas near the bimetallic interface, while the fine grains with more proeutectoid ferrite were obtained in the roll core area away from the interface. Therefore, a higher tensile strength and a better plasticity were obtained for the specimens away from the interface.

Development of process maps based on molten pool thermal history during laser cladding of Inconel 718/TiC metal matrix composite coatings

In the present study, laser cladding of Inconel 718/TiC metal matrix composite coating on SS 304 was carried out using a 2 kW Yb-Fiber laser by preplaced and blown powder method. The molten pool thermal history during the deposition process was monitored using an IR pyrometer and correlated with the evolution of microstructure. The effect of various process parameters, viz. laser power ‘P’ (400 W – 1200 W), scanning speed ‘V’ (200 mm/min to 1400 mm/min) and powder feeding rate (8 g/min – 20 g/min) on the molten pool lifetime and cooling rate is investigated. Molten pool lifetime increased and cooling rate decreased with the decrease of scanning speed and increase of laser power. However, scanning speed had dominant effect on the molten pool lifetime and cooling rate compared to laser power. Moderate molten pool lifetime resulted in the formation of shell-core structure between Inconel 718 matrix and TiC particles. The longer molten pool lifetime (>0.45 s) resulted in complete decomposition of TiC particles rendering brittleness to the coating. The feasibility of detecting TiC particle decomposition in Inconel 718 matrix from the recorded thermal cycles based on multiple solidification shelfs is discussed. At the end, a process map based on a combined process parameter, PD/V2 (spot diameter D) and molten pool lifetime (τ) was developed. An optimum range of molten pool lifetime i.e. 0.25 s < τ ≤ 0.45 s was found to result in a good quality of coating with the formation of shell-core structure both in case of preplaced and blown powder laser cladding method.

Effect of preheating/post-isothermal treatment temperature on microstructures and properties of cladding on U75V rail prepared by plasma cladding method

Rail cladding is a cost-effective approach for track maintenance and protection from rapid growth of mileage and Rolling Contact Fatigue (RCF) phenomenon. In this study, cladding layers are prepared on the surface of a U75V rail substrate using a plasma cladding approach with different substrate preheating temperatures. Preheating of the substrates creates an isothermal treatment for the cladding material after solidification of the molten pools. The effects of these post-solidification isothermal treatment temperatures (480°C, 340°C, and 200°C) on microstructures, mechanical properties and corrosion resistance are studied. The results indicate that the post-isothermal treating temperature affects the fractions of granular bainite, upper bainite, lower bainite, martensite and M/A island in the microstructure. The hardness of cladding layers is higher than that of the U75V substrate, and slightly increases as the pretreating temperature decreases. The specimen prepared at 340 °C has the highest tensile strength, which is 14.5% higher than the U75V rail. The interface between the cladding layer and the substrate also processes a strong bonding with the bonding strength of 789 MPa. Based on the comprehensive performance, the post-isothermal treating temperature of 340 °C is most suitable for cladding on the U75V rail. The plasma cladding process followed by post-isothermal treatment proves to be a flexible and effective approach to manipulate the microstructure of the cladding and restore the properties of the rail substrate.

On the constancy in wear characteristic of large area TiC–Ni coating developed by overlapping of TIG arc scanning

Large-area TiC–Ni coating deposited through the overlapping of single-line TIG arc scanning under different welding current exhibited superior uniformity at 0% (end to end) over 50% overlapping. The micro-hardness value measured laterally on the coating showed that the majority of the hardness values are within 500–1500 HV for 50% overlapping, whereas, for 0%, the hardness readings are random. The sliding wear test of the coating executed against SiC abrasive-disc indicated a large discrepancy in the average wear for test specimen with 0% overlapping as compared to 50%. The results indicated the viability of a large-area hard and wear-resistance TiC–Ni coating by the TIG cladding method, which unveiled sufficient constancy in the performance for higher overlapping of TIG arc scanning.

Evaluation of the mechanical properties of WC-Ni composite coating on an AISI 321 steel substrate

In this study, The WC-Ni composite powders were fabricated by the electroless plating of nickel-phosphorus, followed by the appliance of the obtained particles as a coating on an AISI 321 steel by laser cladding method. Effects of main laser parameters, including power, scanning speed, and powder feed rate on the geometric properties were reviewed. The optimum single-pass specimen was chosen after considering the geometrical shape, dilution, and crack and porosity amount of the single-pass specimens. It was found that the increase in laser power and powder feed rate results in the rise of the height and the width of the coatings. In contrast, coatings with lower height and width were achieved by employing lower laser power and powder feed rates. The procedure was followed by the laser cladding of the WC-Ni powders on 321 steel substrate under the optimum coating parameters with a variety of overlap amounts; 30, 50, and 70 percent. By investigating the formed phases and microstructure of the overlap specimens, the 70 percent overlap coating was chosen as the optimal one. Mechanical and wear tests were conducted on the optimal overlap specimen. Experiments indicated that the hardness, elasticity modulus, and fracture toughness of the coating were, respectively, 1457 Vickers, 6.24 Mpa.m1/2, and 250 GPa. The micro-hardness of the WC-Ni coating was 1.2–1.6 times higher than the WC-Ni, WC-Co and WC-Co-Ni coatings, made by thermal spray coating. Also, the toughness of the coating was 1.5 times higher than the WC-Co thermal sprayed coat. The elasticity modulus of the WC-Ni coating (250 GPa) was 1.1 times more than the WC-Co coating manufactured with the laser cladding method.

Examination of the sliding wear of bronze coatings on railway buffer heads

In this study, results of aluminum bronze coatings (CuAl9Fe3) and manganese bronze coatings (CuMn11Al8Fe3Ni3) deposited on specimens made of S355J2 steel using the laser cladding method are presented. This research was carried out to learn the wear mechanisms and tribological parameters of the analyzed bronze coatings in terms of their applicability for railway buffer heads, instead of covering the latter with graphite grease, which entails several disadvantages. It was found that the laser cladding method allows obtaining durable coatings of aluminum bronze (CuAl9Fe3) and manganese bronze (CuMn11Al8Fe3Ni3) on a substrate made from S355J2 steel. Microscopic examination performed after laser cladding of the above described bronzes showed the presence of three zones: the coating, the heat affected zone, and the substrate. The CuMn11Al8Fe3Ni3 manganese bronze coating was characterized by a significantly higher hardness (236.9 HV) than in the case of the CuAl9Fe3 aluminum bronze (181.5 HV). Based on the obtained results, it was found that aluminum bronze coatings had higher wear resistance in comparison to manganese bronze coatings, which may be associated with a higher fraction of Cu2O and Al2O3 phases. The results obtained indicate that the use of a CuAl9Fe3 coating allows for a significant reduction of sliding wear compared to uncoated samples (average wear was reduced by approx. 89.36%), while the use of graphite lubricant allows for an average wear reduction of ca. 91.35%. SEM examination of the specimen surfaces coated with aluminum and manganese bronze showed visible signs of scratching, plowing and micro-cutting, which proves the sliding nature of the specimen wear.

Evaluation of the mechanical properties of WC-FeAl composite coating fabricated by laser cladding method

WC-Co coating, which is a subcategory of Tungsten Carbide-based coatings, is prominent among a variety of industries. However, because of its expense, poisoning, and low corrosion resistance of Cobalt in acidic environments, alternative compositions have been designed. One of these alternatives is the Iron Aluminide intermetallic compound which can replace Cobalt. This study investigates laser cladding of WC-FeAl powder on a 321 Stainless-Steel substrate. WC-FeAl powders were synthesized by mechanical alloying of initial Aluminum and Iron powders, milled for 20 h, followed by an hour of annealing at 800 degrees Celsius. Then, the annealed particles were mechanically alloyed with WC powders for 50 h. The result of the X-ray diffraction (XRD) analysis showed that no brittle and destructive phase was formed during synthesis. Subsequently, powders were coated on the stainless-steel substrate by laser cladding method. Effect of the main parameters of the laser cladding, including laser power, laser probe velocity, and powder spray rate, on the coating properties, such as porosity, geometry, thickness and, dilution were studied. Results indicate that with a higher power of the laser, the penetration depth and the width of the coating increased. Besides, with a higher velocity of the laser probe, dilution and penetration depth decreased. Furthermore, the Higher rate of powder spray led to a thicker coating. The optimum parameters of different samples were 250 W power, 4 mm/s probe velocity, and 400 mg/s powder spray rate. Evaluation of the mechanical properties indicated that the 1600 Vickers hardness, 5.7 MPa.m1/2 fracture toughness, and 355 GPa Young's modulus were obtained. Besides, The evaluation of the mechanical properties of the coating showed that the hardness, fracture toughness, and elasticity modulus are 1600 V, 5.7 MPa.m1/2, and 355 GPa respectively. Obtained results revealed that in comparison with the WC-FeAl composite coating with 500 ppm additional Boron and WC-Co coating both fabricated by thermal spray coating, for the WC-FeAl coating studied in this investigation, respectively the hardness is 1.16 and 1.21 times higher and the fracture toughness is 2.5 and 2.8 times higher. As well, Young's modulus of the coating was 1.56 times higher than the WC-Co coating made by the laser cladding method.

Microstructural evolution and corrosion properties of Ni-based alloy coatings fabricated by multi-layer laser cladding on cast iron

To solve the problem of brittleness at the bonding interface, the multi-layer laser cladding method was carried out to fabricate Ni-based alloy coating on the compacted graphite cast iron. The effect of dilution rate on the microstructure and corrosion behavior of the coatings were investigated. The results showed that the volume fraction and the secondary dendrite arm spacing of the dendrite increase significantly with the increasing number of the deposited layers. The dendritic phase in the coatings changed from γ-Fe phase to γ-(Fe, Ni) phase, and the interdendritic phase transformed from martensite phase to M7C3 (M = Fe, Cr) phase with the decrease of the dilution rate. The lattice parameter of the dendritic phase decreased gradually, as the increase of Ni content. The corrosion tests show that the coating with six deposited layers exhibited the best corrosion resistance at room temperature in 3.5% NaCl solution. The corrosion mechanism changed from severe intragranular corrosion to pitting corrosion and intergranular corrosion. According to the analysis results of electrochemical impedance spectroscopy curves, Mott-Schottky curves, and point defect model, the improvement of the corrosion resistance was attributed to the high compactness and resistance of the passive film, which provided fewer oxygen vacancies in the corrosion process due to the increase of Ni and Cr concentration of the coating.

Behaviour of TiC Particles on the Co50‐Based Coatings by Laser Cladding: Morphological Characteristics and Growth Mechanism

H13 steel surfaces are covered by coatings of Co‐based alloy with 0, 10, 20, and 30 wt. % TiC using the laser cladding (LC) method. The morphological characteristics, growth mechanism, and the mechanical properties of TiC on the microstructure of the coatings were studied. The results show that TiC in the TiC/Co50 composite coating is composed of two parts: incompletely melted TiC and in situ TiC. TiC content has a great effect on the morphology of TiC, and it exists in different shapes: original TiC, fine‐particle TiC, segregated TiC, petal‐shaped TiC, and branch‐shaped TiC. Additionally, the morphology of TiC in different areas of the coating is different, while TiC size gradually increases from bonding zone to surface. In the 10% TiC+Co50 coating, TiC mainly appears as undermelted, fine particles, precipitates, and having shapes of polygons and petals. From the bottom of this coating, the number of petal‐shaped TiC has increased, and the particle size is also enlarged. In the 20% TiC+Co50 coating, the TiC in the coating mainly presents as undermelted, fine particles, and dendritic morphology. From the bottom of this coating to the surface, the particle size of the undermelted TiC shows a clear gradient change. Finally, the 30% TiC+Co50 coating does not have in situ TiC, and there is no obvious gradient change in the particle size of undermelted TiC. After coating by the LD method, the surface hardness is strongly enhanced. The average hardness of Co50 alloy, Co+10% TiC, and Co+20% TiC composite coatings is 499 HV0.2, 552 HV0.2, 590 HV0.2, and 824 HV0.2, respectively. These values are 2.4–4.0 times harder than that of the H13 substrate. The wear resistance of Co50 alloy, Co+10% TiC, and Co+20% TiC composite coatings is greatly higher than that of H13 steel, showing excellent wear characteristics. The friction coefficient of the coatings which have TiC is very stable. Therefore, the coatings can satisfy the requirement of tool steels applications. Additionally, the wear mechanism of the coating at room temperature is mainly brittle spalling, adhesive, and ploughing. At 700°C, the wear mechanism is mainly oxidation and fatigue.

Wear characteristic of TiC coated AISI 1020 mild steel fabricated by TIG cladding method

TiC composite coating was fabricated on AISI 1020 mild steel substrate by preplacing of TiC powder and subsequent TIG cladding method. A hard and wear resistance composite coating with improved bonding between the TiC particles and the steel matrix was obtained. Vickers micro-hardness tester was used to measure the micro-hardness values of the coated samples for different processing conditions. Pin shaped samples were extracted from the TiC coated tracks by wire-EDM, and sliding abrasive wear test was performed against SiC abrasive disc with the help of a pin-on-disc type wear tester. The effect of processing current was analyzed on the micro-hardness and wear properties of the coated substrate. Based on the heat input, which was controlled through processing current during the TIG cladding process, dilution of TiC on steel matrix changes and consequently the hardness and wear properties of the TiC coating was varying.

Sliding Wear Examination of New Protecting Coatings on Railway Buffer Heads

Abstract The paper presents the results of tests of sliding wear of bronze coatings made on the surface of specimen made of S355J2 steel by laser cladding method. On the basis of the conducted tests it was found that the wear of the specimens with CuAl9Fe3 bronze coating is characterized by average values which are close to lubricated specimens. In addition, the registration of friction coefficients of particular couples showed very similar characteristics of these two friction couples and friction coefficient values at a very similar level. This allows to assume that the currently used method of protecting railway buffer heads, consisting of periodically covering their surface with lubricant, can be replaced with another, more durable, based on bronze protection coatings.

Study on textured CBN grinding wheel by laser cladding

In this investigation, in order to improve bonding strength between superabrasive/metal matrix/grinding substrate, life span of grinding wheel, and grinding using small grits in continuous grinding simultaneously to fit for high speed and high precision machining in industry, coaxial powder feeding laser cladding method with CAD/CAM technology is introduced to manufacture textured CBN/CuSnTi–grinding wheels. The morphology of CBN grit on laser-cladding layer under optimized laser-cladding parameters and a pit created by fallen-off CBN on laser-cladding layer with lower laser–cladding energy density are observed by scanning electron microscope (SEM). The element distributions of interfaces of CBN/CuSnTi/AISI 1045 are analyzed by SEM and energy disperse spectroscope (EDS). The morphology and elements distribution of residual resultants on the surface of CBN grits etched by nitric acid are analyzed by SEM and EDS. Comparative-grinding process between laser cladding–grinding wheel (LCGW) and customized electroplated grinding wheel (EGW) is analyzed with grinding forces and temperature aspects respectively. The wear morphology of CBN grits on LCGW after grinding is observed by SEM. The results show that CBN grit with integrate cutting edges can protrude 50% height of its diameter on laser-cladding layer under optimized laser–cladding parameters. Fe, N, Ti, and B segregates attached to the interfaces of CBN/CuSnTi/AISI 1045 with Cu and Sn distributed uniformly in the laser-cladding layer. Residual resultants on CBN can be divided into two parts based on the distances from the surface of CBN grits. The grinding forces (Fz and Fy) and grinding temperature from LCGW are lower than those from EGW. The wear conditions of CBN on laser cladding are three parts: microfracture, cleavage plane, and wear-out.

Fatigue Analysis of Ladle Shell and Prediction of Lining Thickness

The fatigue analysis of steel cladding and prediction method of lining thickness have been studied. The traditional empirical estimates and operational adjustments are not accurate enough. The finite element strength analysis and fatigue analysis of ladle cladding are carried out. A prediction model for the thickness of ladle lining is established. A BP neural network life prediction model is proposed. Then the model is used to solve the problem. The service life of ladle lining is predicted. The actual use of ladle lining is more accurately understood. The service life of ladle lining is increased and the service life of ladle is prolonged.