Cladding Technology Research Articles

Laser cladding manufacturing of TiC + TiBx reinforced FeNiCrTi0.3Al0.3 high entropy alloy composite coating: Effects on corrosion and tribology

In this work, FeNiCrTi0.3Al0.3 HEA composite coatings were successfully fabricated on the surface of Ti-6Al-4V substrate by laser cladding technology. The influence mechanism of LaB6 + B4C rare earth (RE) phase on phase composition, microstructure, microhardness, corrosion resistance and tribological properties of HEA coatings were characterized. The result showed that the addition of RE phase could promote the in-situ reaction to generate TiC + TiBx. And it could alter the flow in the molten pool and produce heterogeneous nucleation. The equiaxed crystal to columnar crystal transition in the molten pool was affected. With the addition of RE phase, the maximum average microhardness of HEA composite coating reached 875.2 HV0.2, which was 2.36 times of Ti-6Al-4V substrate, indicating that the hard phase generated in-situ effectively improved the resistance of plastic deformation. The corrosion resistance of HEA composite coating strengthened by RE phase was improved as well. The corrosion property of C3 coating was optimal, and the corrosion current density was 1.79 × 10−5A/cm2, the charge transfer resistance reached to 4.48 × 105 Ω cm2, indicating that HEA composite coating could generate a passivation film which was relatively denser than the substrate and had better corrosion resistance during corrosion. Through XPS analysis, Ti, Al and Cr were found as the key elements for the passive film generation of HEA composite coating. After adding RE phase, HEA composite coating produced dense passive film and good forming quality (less cracks and pores, fine and dense grains). Compared with C0 coating, HEA composite coating could not produce occluded cell corrosion (OCC). During tribology test, the enamel layer could generate on the surface of C2 composite coatings, due to the effect of friction ball on tearing and compacting, which was of great significance to protect the coating.

Effect of nano-ZrO2 protective layer on the microstructure and surface property strengthening mechanism of underwater wet laser Fe-based cladding layer

Underwater wet laser cladding technology has become one of the research hotspots in the marine engineering, but the existence of the water environment inevitably leads to process instability and defects. In this study, the nano-ZrO2 protective layer was used to increase the viscosity of the molten pool surface to resist the impact force generated by the high-speed water jet, and the underwater wet laser Fe-based cladding layer with good forming quality and desirable performance was successfully prepared. The nano-ZrO2 protective layer improved the formability of the cladding layer and guaranteed the depth of the melt pool, while reducing the depth of the heat affected zone. The addition of nano-ZrO2 particles reduced the average grain size of the cladding layer from 4.90 μm to 3.66 μm. In addition,the corrosion resistance of the cladding layer was greatly improved with the application of the nano-ZrO2 protective layer, with the evident passivation region of 0.74 V. The wear rate of the cladding layer with the nano-ZrO2 protective layer (0.64×10-15m3N-1m-1) was significantly lower than that of the substrate (9.01×10-15m3N-1m-1), and the excellent wear resistance of the cladding layer with nano-ZrO2 protective layer benefited from the good carrying capacities and high microhardness of the microstructure with ZrO2 particles. This study reveals the strengthening mechanism of nano-ZrO2 protective layer on the Fe-based cladding layer, which can provide theoretical guidance for the development of the underwater laser cladding.

Numerical simulation and surface morphology of laser cladding of nickel-based C276 alloy coatings on AerMet100 steel surface

In order to rationally characterize the laser cladding process and effectively predict the processing results, the temperature field and convective heat transfer at the solid-liquid interface were simulated using ANSYS software. Under the selected process parameters, C276 nickel alloy powder was clad on the surface of AerMet100 steel by laser cladding technology, and the microstructure of the cladding layer was observed to investigate the effects of laser power and scanning speed on the laser results. The effect of laser power and scanning speed on the laser results was investigated. The results show that the best coating performance is obtained when the laser power is 1400 W and the scanning speed is 14 mm/s. When the laser power is 1400 W, the scanning speed is increased from 12 mm/s to 16 mm/s, the dilution rate of the coating is increased from 0.385 to 0.423, and the height of the coating is decreased from 0.706 mm to 0.428 mm. When the scanning speed is 14 mm/s, the laser power is increased from 1000 W to 1600 W, the dilution rate of the coating is increased from 0.375 to 0.511, and the height of the coating is increased from 0.393 mm to 0.662 mm. The laser power has a large effect on the height, width, depth and dilution of the coating, while the scanning speed has a large effect on the average particle size of the coating.

Coaxial Laser Wire Deposition of AISI 316L steel - research on influence of processing parameters

Laser cladding technology is a well-established process, commonly used for deposition of improved-property coatings, repair of machine parts and additive manufacturing. Currently, in terms of application of laser cladding, the method based on powder deposition is much more common, as the use of an adapted nozzle allows the coaxial and direction-independent feeding of additional material into the weld pool. However, laser cladding with powder also has some significant drawbacks, e.g., limited powder feeding and melting efficiency, lower productivity and the resulting dust that poses a health risk to operators. The solution to these limitations is the use of additional material in the form of wire. To maintain the ability to coaxially feed the wire to the laser beam interaction point, a specialized cladding head is necessary. In mentioned system the laser beam, while being passed through the optical system, is divided into three separate beams that are focused on the substrate on the working point of the head. In this study, the COAXwire cladding head was integrated into the robot station and laser cladding process was carried out to determine the influence of the processing parameters on the deposition results. The parameters of the cladding system were identified, including the measurement of laser beam caustic. The experimental trials were carried out using AISI 316L wire deposited on S420MC substrate. The effect of the processing parameters on the geometry of the clad was determined with particular emphasis on the wire feeding.

Effect of GO content on microstructure and mechanical properties of Ti6Al4V coating reinforced artificial joint.

In this study, we have innovatively proposed a method of in-situ synthesized TiC hard phase to improve the surface mechanical properties of artificial joint materials (Ti6Al4V). In order to explore the optimum graphene oxide (GO) addition, GO/Ti6Al4V composite powders with different proportions (0, 0.5, 1.0, and 1.5 wt.%) were prepared. The homogeneously dispersed GO/Ti6Al4V composite powder was prepared on Ti6Al4V substrate by laser cladding technology. The microstructure, phase composition, and mechanical behavior of GO/Ti6Al4V composite coatings were studied by scanning electron microscope (SEM), optical microscope (OM), energy dispersive spectrometer (EDS), tribometer, hardness tester, and surface profiler. The results showed that the addition of GO could significantly improve the mechanical properties of TC4 substrate. During the preparation of the coating, the grain size of in-situ TiC phase was nanoscale and was distributed between acicular martensite, which played a critical role in enhancing the mechanical properties of the coating. The TiC phase distributed between acicular martensite refine the grain size of phase and improve the cutting resistance of the coating. Nevertheless, excessive GO decreased the fluidity of the molten pool, and micro holes tended to generate in the coating, which had a negative impact on the mechanical properties of the coating. At the GO content of 0.5 wt.%, the microhardness of the GO/Ti6Al4V coating was 1.325 times that of pure Ti6Al4V. Under the friction environment of simulated body fluid solution, the average friction coefficient was approximately 0.307 and the wear rate decreased to 3.5 × 10-7 mm3/N · m.

Microstructure and Corrosion Property of Prepared CoCrW Coatings on the TC4 Surface by Laser Cladding

Ti6Al4V (TC4) is widely used in aerospace, marine equipment, and the petrochemical industry. However, the dense oxide film on the surface of this alloy will be destroyed in reducing acid solution, resulting in surface corrosion in practical application. To enhance the corrosion resistance of TC4 in marine environments, this study employed laser cladding technology to deposit a CoCrW cladding layer on the TC4 alloy surface. Experimental results validated the successful preparation of a dense, crack-free CoCrW layer. The microstructure of the CoCrW layer was characterized by predominant bulk grains and minor equiaxed crystal constituents, demonstrating a robust metallurgical bond to the matrix. Notably, the corrosion resistance of the TC4 surface witnessed a marked improvement, evident from the CoCrW coating’s increased open circuit potential, elevated electrochemical impedance spectroscopy (EIS) radius, phase angle, and impedance modulus values. The corrosion rates of both the TC4 and CoCrW cladding layers escalated with extended immersion time and increased immersion corrosion temperature. However, the CoCrW cladding layer reported minimal mass loss and the least corrosion rate. In summary, the CoCrW coating, when prepared via laser cladding on the TC4 surface, markedly bolstered corrosion resistance.

Investigation on the Ni60-WC composite coatings deposited by extreme-high-speed laser-induction hybrid cladding technology: Forming characteristics, microstructure and wear behaviors

In this work, Ni60-WC composite coatings with 35 wt% WC (Ni65-WC35), 50 wt% WC (Ni50-WC50) and 65 wt% WC (Ni35-WC65) were deposited by the extreme-high-speed laser-induction hybrid laser cladding technology (EH-LIHC), and the forming characteristics, microstructure, hardness and wear behaviors were investigated systematically. Results indicated that all the EH-LIHCed Ni60-WC coatings displayed low-roughness surfaces and even-distributed WC particles, where the dilution ratio and WC's heat-loss increased with the rise of induction heating temperature (T) and WC's content. Crack-free single-layer Ni60-WC coatings could be obtained at T ≥ 600 °C, whereas some micro-cracks were inevitably induced during the multi-layer depositions. The WC particles mainly presented the decomposition/ dissolution-diffusion, collapse-dissolution and decomposition/dissolution-precipitation heat damages, corresponding to the W-rich dendritic/wing-like/filamentary structures, dendritic facet structures and blocky facet structures on the metal matrix, respectively. Under both loading forces of F = 50 N and 80 N, the wear rates Ni60-WC composite coatings presented the order of Ni35-WC65 < Ni65-WC35 < Ni50-WC50. Spalling of the matrix, cracking and crushing of the WC particles were detected on all worn surfaces. The Ni35-WC65 coating possessed the highest contents of WC particles and facet carbides, making its damage threshold and wear resistance enhanced significantly. Nonetheless, the wear debris in Ni65-WC35 coating had formed a metal layer covering on the worn surface, helping to alleviate the damage of the beneath WC particles significantly, therefore it possessed lower wear rate than that of Ni50-WC50 coating.

TiC morphology and corrosion resistance of CrMnFeCoNi+x(TiC) coatings prepared by laser cladding

The corrosion resistance of CrMnFeCoNi coatings with varying TiC contents and the evolution of TiC within these coatings were comprehensively investigated. These CrMnFeCoNi coatings, with different TiC concentrations, were fabricated using laser cladding technology. The behavior of TiC evolution in CrMnFeCoNi coatings was observed to follow a distinct pattern. At a TiC loading of 2 wt%, TiC exhibited a dispersed distribution. Interestingly, in coatings loaded with 4 wt% TiC, TiC was observed in various shapes, including elongated, square, petaled, and circular forms owing to the melting of TiC particles under the influence of a high-energy laser beam. The convection action of the molten pool combined several unmelted, partially melted, and precipitated TiC particles, resulting in diverse shapes. Furthermore, increasing the TiC content to 10 wt% led to the aggregation and fusion of TiC into clusters. Additionally, the electrochemical corrosion resistance behavior of CrMnFeCoNi coatings with varying TiC content displayed a significant correlation with the TiC concentration. As the TiC content increased, the galvanic corrosion resistance also increased. At lower TiC content levels, a higher number of electrochemical cells formed between the CrMnFeCoNi matrix and the dispersed TiC, leading to an elevated corrosion rate. In contrast, as the TiC content increased, the dispersed TiC phase fused together, reducing the likelihood of electrochemical cell formation. Notably, the electrochemical corrosion resistance of the CrMnFeCoNi coating containing 10 wt% TiC resembled that of the TiC-free coating.

Microstructure evolution, mechanical and abrasive wear properties of NiCrSiB-SiC composite coatings prepared on 16Mn low-carbon steel by Ni-based alloy catalyzed SiC decomposition

In this study, NiCrSiB-SiC composite coatings were prepared on 16Mn low-carbon steel by vacuum cladding technology using SiC and NiCrSiB mixed powders as raw materials for enhancing their wear resistance. The effects of different content of SiC particles on the microstructure evolution, mechanical and abrasive wear properties of the coatings were investigated. The results showed that SiC particles in all the NiCrSiB-SiC composite coatings with different SiC contents were completely decomposed into C and Si under the catalysis of Ni-based alloy. The out-diffused Si into the coating mainly led to the formation of the Ni3Si eutectic phase, while the out-diffused C introduced M7C3, M3C2, M2(C, B) and other hard phases. Besides, C also diffused to the substrate, leading to a carburizing effect, which remarkably enhanced the mechanical properties of the substrate. In the NiCrSiB-SiC composite coatings with high SiC content, the decomposition of SiC led to the remaining graphite phase. However, once the concentration of SiC was over high, excess graphite would deteriorate the compactness and adhesion of the coating, weakening its wear performance. The nanoindentation and abrasive wear experiments revealed that the composite coating with 5 wt% SiC particles had lower elastic modulus (E), higher hardness (H), H/E, and H3/E2, and its wear volume was only 1/10 of that of the substrate, indicating the best mechanical and wear properties. The excellent wear performance can be attributed to the combination of the in-situ formed carbides and borides hard reinforcing phases and the tough coating matrix composed of Fe and Si dissolved γ-Ni and Ni3Si eutectic phase.

Wear‐Resistance of High‐Entropy Alloy Coatings and High‐Entropy Alloy‐Based Composite Coatings Prepared by the Laser Cladding Technology: A Review

With the continuous development of the aviation and aerospace industries, there is an increasing demand for surface coatings that can enhance the wear‐resistance and lubricity of substrates. High‐entropy alloy (HEA) coatings and high‐entropy alloy‐based composite coatings (including ceramic and lubricating phases) have attracted large attention, which is due to their excellent properties. They have, therefore, developed rapidly in the past decade. This article reviews the current status of research on the tribological properties of the HEA coatings and HEA‐based composite coatings that have been prepared by laser cladding technology. The focus is then on the wear‐resistance and wear‐reduction mechanism of the coatings. Furthermore, the review analyzes the influence of element addition, atomic ratio change, and process parameters on the coating organization and properties. The problems that have to be solved in the development of tribology‐based HEAs coatings, and the expected future development of HEA the coatings, are also discussed.

Effect of process parameters on microstructure and tribological properties of Ni60A/Cr3C2 laser cladding on 60Si2Mn steel

To improve the surface performance and service life of the arc-shaped nail teeth, a key component in pre-sowing film recovery machines, Ni60A/Cr3C2 composite coatings were deposited on the surface of 60Si2Mn steel using laser cladding technology. A numerical simulation of the temperature field was conducted for different process parameters based on the ANSYS secondary development language APDL and life–death element technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), three-dimensional morphometry, and X-ray photoelectron spectroscopy (XPS) were also used to analyze the microhardness, microstructure, elemental distribution, and wear resistance of the composite coatings, respectively, to investigate the optimum combination of laser coating parameters. Results show that the temperature field demonstrates a “comet-like” distribution, forming an elliptical melt pool. The average error between melt pool depth and experimental results under this model is 5.1 %. The process parameters affecting the quality of the coating are presented in order of priority: scanning rate, powder feed rate, and laser power. Composite coatings exhibit precipitation of new phases such as γ-Ni-based, NiO, M7C3 (M = Cr, Mn), and M23C6 type. The optimum combination of laser cladding parameters (T6) is 1800 W laser power, 5 mm/s scanning rate, and 8 g/min powder feed rate. T6 coating exhibits a good metallurgical bond with the substrate and a microhardness of 902 HV0.1. Wear of the T6 coating is mainly in the form of abrasive wear, while wear of the base material is in the form of severe adhesive and abrasive wear. The wear and surface roughness of the T6 coating is only 13 % and 39.5 % than those of the 60Si2Mn base material, and the wear depth is reduced by 77 %. This study can provide a reference value for the use of surface technology to enhance the comprehensive performance of agricultural machinery and equipment.

Effect of LaB6 addition on the in-situ synthesis of TiBx/TixNiy/TiC reinforced Ni-based composite coatings

The TiBx/TixNiy/TiC reinforced Ni60 composite coatings were successfully prepared on the surface of 35CrMoV substrate using the laser cladding technology by adding different content of LaB6 (0, 0.5, 1.5, 2.5 wt%) powders into the mixture of TC4 (Ti6Al4V) and Ni60 (94 wt% Ni60, 6 wt% TC4). The phase composition, microstructure, element distribution and chemical composition of the cladding layer were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) with energy spectrum analysis (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The reinforced phases in the cladding layer were mainly composed of TiB2, TiC, TiB, Ti2Ni, NiTi and Ni3Ti. The addition of LaB6 did not affect the phase composition, but the grains are obviously refined and the distribution of Ni, Cr and Ti elements is uniform at the addition of 1.5 wt% LaB6 addition. The cladding layer obtained excellent tribological and mechanical performance with the addition of 1.5 wt% LaB6, and the hardness, average friction coefficient and wear volume of the cladding layer reach 808 HV1, 0.183, and 8943 μm3, respectively. The reasonable addition of LaB6 significantly improves the friction and mechanical properties of the cladding layer.

Research on Surface Strengthening Treatment and Performance of Sewing Machine Shaft Parts

In actual production, shaft parts are affected by the working environment, and are prone to failures such as wear, deformation, corrosion, etc. If the parts that are scrapped due to service damage can be repaired, it can not only save huge economic and time losses, but also It can also improve the utilization rate of resources, in line with the national sustainable development strategy. In this paper, laser cladding technology is used to strengthen the surface of the laser cladding coating for sewing machine shaft parts, and analyze the microstructure, hardness, friction and wear properties of the cladding layer after laser cladding. It is concluded that the average hardness of the cladding layer is about 740.3HV, which is about 2.9 times that of the substrate; the wear loss of the cladding layer is greatly reduced, which are 34%, 40% and 48% of the substrate, respectively, which are less than half of the wear amount. It can be seen that laser cladding on the surface of shaft parts can improve the surface quality of the parts and prolong the service life of the parts.

Effect of Y2O3 Content on Microstructure and Corrosion Properties of Laser Cladding Ni-Based/WC Composite Coated on 316L Substrate

To improve the corrosion resistance of 316L substrate and lengthen its useful life in marine environments, Ni-based/WC/Y2O3 cladding layers with different Y2O3 contents were fabricated on 316L stainless steel using laser cladding technology. The influence of Y2O3 additives on the microstructure and properties of the cladding coatings was investigated by using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, a microhardness tester, an electrochemical workstation and a tribometer. Results show that the metallurgical bonding is well formed between the coating and the 316L substrate. The coating consisted primarily of γ-Ni phase and carbides. Adding an appropriate amount of Y2O3 can effectively refine the microstructure and inhibit the precipitation of the carbide hard phase; in addition, the added rare earth element can promote the solid-solution-strengthening effect of the cladding coatings, thus improving the microhardness and wear resistance of the cladding coatings and their electrochemical corrosion property in 3.5 wt% NaCl solution. The hardness of the Ni-based/WC coatings was substantially higher than that of the substrate, and it was greatest at a Y2O3 content of 1%. The corrosion and wear resistance of Y2O3-modified Ni-based/WC composite coatings are significantly better than those of the composite coating without Y2O3.

Effect of magnetic field assisted thermal diffusion on microstructure and properties of titanium alloy laser cladding coating

Ti–Al composite coating was prepared on the surface of a titanium alloy by the laser cladding technology and coaxial powder feeding under argon protection. The cladding material was AlSi10Mg aluminum alloy powder. The intermediate sample was thermally diffused at high temperature for 6 h and then placed in a certain intensity of the alternating electromagnetic field until completely cooled. The alloy substrate and coating solidified under the action of the alternating electromagnetic field, and the surface coating of a high strength titanium alloy was obtained. The morphology and microstructure of the composite coating were analyzed by SEM, XRD, and energy dispersive spectroscopy (EDS), and the hardness of the coating was measured. The results showed that the high temperature thermal diffusion promoted the interatomic diffusion; repaired some defects, such as cracks and pores; and eliminated the elemental metals that did not participate in the reaction, and the surface hardness of the coating joint reached the maximum. The electromagnetic stirring makes the titanium alloy coating and substrate bond well, the joint is relatively straight, the number of cracks and pores is obviously reduced, and the comprehensive performance of the coating is improved.

High-temperature oxidation behavior of laser-cladded refractory Al0.75NbNi0.1Mo0.1Cr0.5Si0.1Wx high-entropy coatings

Refractory High Entropy Alloys (RHEAs) have great potential for ultra-high temperature environments and are one of the potential candidates for high temperature applications. In this work, a series of Al0.75NbNi0.1Mo0.1Cr0.5Si0.1Wx (x = 1, 1.5, 2) refractory high-entropy alloy coatings is prepared by laser cladding technology. The microstructure and oxidation behavior at 1000 °C and effect of changing oxidation temperature on oxidation behavior of the coatings is investigated. The results show that Al0.75NbNi0.1Mo0.1Cr0.5Si0.1Wx RHEA coatings are composed of BCC, W5Si3 and AlNi3 phases. The microstructure of RHEA coatings exhibits dendritic-cellular grain transition with increasing W content. The specific mass gains of coatings due to high temperature oxidation is 65.5 mg/cm2 for x = 1, 8.5 mg/cm2 for x = 1.5 and 14.5 mg/cm2 for x = 2 at 1000 °C for 70 h. After oxidation in 1000 °C for 70 h under air atmosphere, a protective oxide film (such as Al2O3 and SiO2) adhere around NiWO4 on the alloy coatings, which impedes the inward oxygen transport. Moderate addition of W elements is found to be beneficial in enhancing the oxidation resistance of coatings. However, excessive addition of W elements prevents the formation of protective oxides (Al2O3 and SiO2) and reduces the high-temperature oxidation resistance of the coatings. With the increase of oxidation temperature, simple oxides are significantly reduced while compound oxides are increased on the surface of the coatings. The surface appears hill-shaped oxides with the increase of NiWO4.

Study on Erosion Behavior of Laser Wire Feeding Cladding High-Manganese Steel Coatings.

High-manganese steel (HMnS) coating was prepared using laser wire feeding cladding technology. Erosion damage behavior and erosion rate of both the HMnS coating and the HMnS substrate were investigated at room temperature using an erosion testing machine. SEM/EDS, XRD, EPMA, and microhardness analyses were used to characterize the cross sections of the coating and matrix, as well as the morphology, phase composition, and microhardness of the eroded surface. The phase composition, orientation characteristics, and grain size of the eroded surfaces of both the coating and substrate were examined by using the EBSD technique. The erosion mechanism under different erosion angles was revealed. By analyzing the plastic deformation behavior of the subsurface of the HMnS coating, the impact hardening mechanism of the high-manganese steel coating during the erosion process was investigated. The results demonstrated that the HMnS coating, prepared through laser wire feeding cladding, exhibited excellent metallurgical bonding with the substrate, featuring a dense microstructure without any cracks. The erosion rate of the coatings was lower than that of the substrate at different erosion angles, with the maximum erosion rate occurring at 35° and 50°. The damage to the coating and substrate under low-angle erosion was primarily attributed to the micro-cutting of erosion particles and a minor amount of hammering. At the 90° angle, the dominant factor was hammering. After erosion, the microhardness of both the coating and substrate sublayer increased to 380HV0.3 and 359HV0.3, respectively. Dendrite segregation, refined grains, low-angle grain boundaries, and localized dislocations, generated by laser wire feeding cladding, contributed to the deformation process of HMnS. These factors collectively enhance the hardening behavior of HMnS coatings, thereby providing excellent erosion resistance.

Microstructure and properties of argon arc cladded CoCr x FeMoNiAl high entropy alloy coatings on Q235 steel

Abstract In this paper, the CoFeMoNiAlCr x coatings with different chromium content (x = 0, 0.3, 0.6, 0.9 and 1.2) were prepared by argon arc cladding technology on Q235 steel. The microstructure and phases of the coatings were analyzed by OM, SEM, EDS and XRD. The hardness, wear resistance and corrosion resistance of the coatings were tested by microhardness tester, friction and wear tester and electrochemical workstation. The results show that the highest hardness is obtained in the CoFeMoNiAlCr x=0 high entropy alloy coatings, about 500 HV, which is about 3 times than the hardness of Q235 steel (the substrate). With the chromium content of the CoFeMoNiAlCr x coatings increasing, the wear resistance increases first, and then decreases. When the chromium content is 0.9, the wear resistance of the coating is the highest with the wear loss about 2.6 mg and the friction coefficient about 0.52. The corrosion resistance of the coatings decreases with a small amount of chromium addition. When the Cr content in the coating is close to the atomic ratio, the content of the body-centered cubic phase structure increases, and the face-centered cubic phase structure appears in the coating.

Preparation process and mechanical properties of laser cladding gradient molybdenum coating on copper alloy

Different types of Mo coatings were prepared on the surface of a copper alloy via laser cladding technology in this study to address the problem of low hardness of copper alloy current-carrying friction subsets. Meanwhile, the problems of high reflectivity of copper alloy materials to infrared laser light and mutual insolubility of Cu and Mo were solved by introducing an intermediate layer structure, and the coating process was optimized to obtain a coating with excellent formation. The microstructure, hardness, and interfacial shear bond strength of coatings were tested. Results showed that the Mo coating prepared using a plasma-spheroidized powder had a lower dilution rate and finer and tighter grain growth compared with the Mo coating prepared by crushing agglomerated powder. The coating phase mainly consisted of Mo, Ni3Mo, MoO2, and Cu0.81Ni0.19. The unfused particles present in the plasma-spheroidized powder coating acted as a second hard reinforcing phase, which could significantly increase the hardness of the coating. Three kinds of coatings exhibited strong bond strength, and coatings prepared from different powders fractured in diverse ways. In sum, the plasma-spheroidized Mo coating prepared using the three-way powder feeding method not only had good formation but also possessed the most excellent mechanical properties.

Study on overlap rate and machinability of selected laser melting of maraging steel

Abstract In order to investigate the material properties of maraging steel laser additive manufacturing, the cladding layers with different overlap rates on the surface of 18Ni300 were prepared by laser cladding technology, and the morphology, microstructure, and hardness of the cladding layer with different overlap rates were analyzed by various means. The results show that the macroscopic morphology of the cladding layer mainly presents three states under different overlap rates, and the change of overlap rate has no effect on the microstructure in the same area of the cladding layer, but does have an effect on the size of the cladding layer. In the end, the optimum overlap rate is 50%, the surface is smooth, the inner is free from defects, the bonding effect is good, and the metallographic structure is even with high hardness. Milling experiments were carried out on the material after laser additive manufacturing, and the surface morphology was observed, confirming a smooth and well-flattened surface with a roughness of 0.342 μm had been obtained. The suitable overlap rate can make the coating surface smoother, reduce the subsequent processing loss, and improve the production efficiency and powder utilization rate while ensuring the coating quality.