Clad Zone Research Articles

In Situ Formation of Laser-Cladded Layer on Thin-Walled Tube of Aluminum Alloy in Underwater Environment.

The first study of thin-walled aluminum-alloy tubes with underwater-laser-nozzle in situ melting technology was carried out. The study mainly covered the influence of the water environment on the laser melting process, melting appearance, geometric characteristics, microstructure, regional segregation and microhardness. During the transfer of the cladding environment from air to water, the uniformity of the cladding layer became poor, but excellent metallurgical bonding was still obtained. The dilution rate (D) decreased from 0.46 to 0.33, while the shape factor (S) increased from 4.38 to 5.98. For the in-air and underwater samples, the microstructure of the melting zone (MZ) and the cladding zone (CZ) were columnar dendrites and equiaxed grains, respectively. In addition, the microstructure of the overlapping zone (OZ) was composed of columnar dendrites and equiaxed grains. The underwater average grain size was smaller than that of in-air. In addition, the water environment was beneficial for reducing the positive segregation in the columnar dendrite region. Compared with the in-air cladding sample, the precipitated phases in the OZ of the underwater cladding sample reduced. Under the combined action of grain refinement and precipitated phase reduction, the microhardness value of the underwater OZ was higher than that of the in-air OZ.

Laser cladding of Inconel 713 LC with Stellite 31 powder: statistical modeling and optimization

In the present study, laser cladding of Inconel 713 LC alloy with Stellite 31 powder was carried out using a 400 W pulsed Nd:YAG laser. Central composite design was employed to study the influence of input variables including pulse width, laser frequency, and laser speed on the output responses such as the clad geometry (clad height and clad width), dilution ratio (DR), and hardness. The results indicate that that the pulse width and laser frequency have a direct influence on the clad width, and DR but a reverse influence on the clad height and hardness. However, the influence of laser speed is the opposite of the influence of pulse width and laser frequency. The results depict that the hardness value decreases when the DR raises. By increasing the DR, the concentration of Co and Cr elements in the coating layer reduces, leading to a drop in the hardness. Simultaneous optimization was employed to optimize the cladding process. The pulse width of 12.19 ms, laser frequency of 20 Hz, and laser speed of 4.85 mm s−1 were found as the optimum parameters. The optimum sample has the hardness value of about 480 ± 5 Hv. This value is significantly higher than the hardness value of the substrate (355 ± 3 Hv). The cobalt solid solution phase and Cr7C3, Cr3C2, W2C, and WC x carbides are observed in the clad zone of the optimum sample.

Evolution of solidification and microstructure in laser-clad IN625 superalloy powder on GTD-111 superalloy

Abstract Nickel-based superalloys, especially GTD-111, are widely used in the aerospace industry. Due to the high amount of Cr, the IN625 superalloy can be a good option for the surface protection of GTD-111. In this study, IN625 powder was cladded on GTD-111 using a pulsed Nd: YAG laser. This study aimed to investigate the effect of laser process parameters such as power, scan speed, and powder feed rate on microstructure development, defects, and hardness of the cladded samples. The results of this study showed that with increasing laser power from 150 to 300 W, the solidification structure tends to form equiaxed grains due to the decreasing GR from 30,751 to 20,058 °C/s and G/R from 1230to 802 °C/mm2. While at the laser power of 300 W, the tendency to form liquated cracks is increased due to the expansion of HAZ and the consequent increase in the reaction of crack-sensitive phases such as γ′, γ-γ′, and MC within the matrix. The tendency to form an equiaxed/coaxial region in the clad zone (CZ) decreased with an increase in the powder feeding rate. The inclination to form lateral porosity increased due to the reduction of the laser time interaction with the sample surface. On the other hand, by increasing the scan speed from 4 to 7 mm/s, the tendency to form cracks in the interface of the clad-substrate and HAZ increases due to the increased stresses caused by cooling. Unlike scanning speed and laser power, with increasing powder feeding rate, the distance between dendritic arms at the bottom of the coating has decreased from 1.12 to 1.02 μm. In this study, it was found that with increasing the heat input, the solidification rate decreases and as a result, more time is created for increasing the coating dilution. The distance between the dendrites subsequently increases and coarsening of carbide particles also occurs.

ARGON-ARC CLADDING OF Q235 LOW-CARBON STEEL BY CO BASE ALLOY DEPOSITION

The Co base layer was obtained without obvious defects by argon-arc cladding (AAC) of Co42A mixed powders (the welding current 160[Formula: see text]A and the welding speed 14[Formula: see text]mm/s). Then, the effect of different process parameters on the microstructure properties of this layer was investigated in detail. The compact clad zone was obtained, which consisted primarily of the fine dendrites; the sizes of the columnar crystals decreased significantly with increasing of the welding speeds. This AAC Co42A layer (the welding current 160[Formula: see text]A and the welding speed 14[Formula: see text]mm/s) had a high hardness due to the actions of the fine grain/solid solution strengthening and the produced multi-phase.

基体取向对激光熔覆修复区域杂晶形成的影响

基体取向对激光熔覆修复区域杂晶形成的影响

Microstructure Analysis of IS2062 Plates Cladded with SS2594 by TIG Welding Process

The power requirement of industries has been growing like anything now-a-days. The components involved in the production of power have also attracted more attention in industrial revolution. The present work focuses on improving the hardness and shear resistance of IS2062 work material used in the manufacturing of fire tubes in thermal power plants. The cladding of surface was carried out by Tungsten Inert Gas (TIG) welding with the use of SS2594 duplex steel as surface coating material. Hardness test results revealed that cladding process have raised the value from 170 to 411. Microstructural analysis has revealed the formation of refined grains at the clad zone due to continuous recrystallization of martensite. It has happened because of higher gas flow rate during welding. Macroscopic analysis has proved the increase in current during the process improved the diffusion of SS2594 material into the base metal IS2062.

Tungsten Inert Gas (TIG) Cladding of TiC-Fe Metal Matrix Composite Coating on AISI 1020 Steel Substrate

TiC – Fe composite coating was produced on AISI 1020 steel by the tungsten inert gas (TIG) cladding process to increase the hardness and wear resistance properties of the substrate. In this paper authors have investigated the effect of process parameters on the microstructure and hardness value of the coated layer. In this TIG cladding process the variable parameter is only current, whereas the other parameters such as scanning speed, standoff distance, and voltage and gas flow rate are fixed. Fe and TiC powders were mixed in the proper ratio of 80wt% - 20wt% and 90wt% - 10wt% respectively. The microstructure and micro-hardness value of the samples were investigated by the scanning electron microscope (SEM) and Vickers micro hardness tester. The result of SEM shows the distribution of the coating powder in the cladded zone. Micro hardness profile shows the variation of the hardness value in the cladded zone as well as in the substrate. The hardness value decreases with increase in distance from top surface of the cladded layer, which is due to difference in cooling rate. Also, the hardness value of cladded layer decreases with increase in current from 140A to 150A. The maximum hardness value of cladded layer was achieved as 262 HV0.05with 140A current and composition of 90 wt.% - 10wt% (Fe - TiC), which was nearly two times higher than that of the as received AISI 1020 steel substrate. Keywords TIG, Microstructure, Micro hardness, Titanium Carbide (TiC), Iron (Fe) powder.

Liquid phase cladding of AlxCoCrFeNi high entropy alloys on AISI 304L stainless steel

AlxCoCrFeNi (x = 0.5, 1, and 1.5) high entropy alloys (HEAs) were synthesized on the AISI 304L stainless steel via liquid phase cladding using a tungsten inert gas (TIG) heat source. To do so, elemental powder mixtures were initially ball-milled and preplaced on the steel substrate followed by TIG surface melting. The process parameters were chosen in such a way that the least possible dilution of the substrate into the clad zone was achieved. It was observed that the dilution rate was dependent on the Al content of the powder mixture. Microstructural assessments revealed that alloying occurred in the initial powder mixture during surface melting and a relatively uniform microstructure was achieved within the clad zone. X-ray diffraction analysis showed that the deposited layer had a dual phase FCC and BCC crystal structure. It was also noticed that increasing of Al content in the HEA raised the volume fraction of BCC/ordered BCC (B2) phase. It also led to a change in the morphology of columnar dendrites to equiaxed ones. Segregations of Al-Ni rich phase and Cr-rich phase at the interdendritic regions were evident in the HEA with low (x = 0.5) and high (x = 1.5) Al content, respectively. The hardness of the clad zone was appreciably dependent on the Al content of the HEA, so that various contents of 0.5, 1, and 1.5 resulted in the microhardness values of 170, 510, and 530 HV0.1, respectively.

Microstructural characteristics and hardness of CoNiTi medium-entropy alloy coating on pure Ti substrate prepared by pulsed laser cladding

A ternary CoNiTi medium-entropy (MEA) alloy coating was successfully fabricated on pure Ti substrate by utilizing pulsed laser cladding. Phase constitutions and microstructural characteristics of the coating were analyzed by combined use of X-ray diffraction, electron channeling contrast imaging, secondary electron imaging, energy dispersive spectroscopy and electron backscatter diffraction techniques. Results show that three zones with distinct microstructures are formed after the pulsed laser cladding treatment: cladding zone (CZ), bonding zone (BZ) and heat-affected zone (HAZ). Dendritic (BCC solid-solution phase)-interdendritic (Ti2Ni type phase) structures are formed in the CZ with many nanoparticles (Ti2Co type phase) dispersed inside the interdendritic structures. The BZ consists of fine acicular grains while the HAZ below the BZ is composed of irregular-shaped bulk grains. Hardness measurements reveal that hardness of the MEA coating reaches 571 ± 46 H V, which is ∼5 times that of the substrate (114 ± 4 H V). Comprehensive analyses show that such high hardness can be attributed to the combined contributions from solid-solution hardening of the BCC phase and second-phase hardening from the Ti2Ni and Ti2Co type intermetallic compounds.

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.

Microstructural evolution of laser-clad 75Cr3C2+25(80Ni20Cr) powder on Inconel 718 superalloy

Abstract Nickel-based superalloys such as Inconel 718 are widely used in the aerospace industry. The surface properties of Inconel 718 can be improved by the addition of chromium carbide–nickel chromium powder. In this study, 75Cr3C2+25(80Ni20Cr) powder was clad on annealed Inconel 718 superalloy by using a pulsed Nd:YAG laser. The aim of this research is to investigate the effect of laser process parameters such as pulse width, laser frequency and scanning speed on the microstructure and microhardness of the clad samples. It is found that the increasing pulse width and laser frequency or decreasing scanning speed can increase the heat input and the resultant dilution ratio. The clad zone of the samples with a high dilution ratio consists of eutectic structure (γ and Cr7C3). However, the clad zone of specimens with a low dilution ratio is composed of a hypereutectic structure of Cr7C3+(γ+Cr7C3). This microstructure leads to the significant increase in the hardness value in comparison with the specimens with a high dilution ratio, due to the presence of proeutectic Cr7C3 carbides in the hypereutectic structure. The maximum hardness value of the clad zone is found to increase almost 2.5 times that for the substrate in the annealed condition. However, the austenitic and Laves phases are formed in the partially mixed zone. This zone is rather narrow, approximately 30 μm. The grain coarsening occurs in the heat-affected zone of all the deposited specimens. The hardness values of the partially mixed and heat-affected zones are lower than that for the clad zone.

Microwave cladding of Inconel-625 on mild steel substrate for corrosion protection

In the present work, Inconel-625 cladding was performed on a mild steel (MS) substrate through a cost-effective microwave technique. Cladding was performed in an industrial microwave oven operated at 1.2 kW and 2.45 GHz. The XRD observation indicates the presence of Laves and carbide phases in addition to a Ni-Cr-Fe based face-centered-cubic (fcc) matrix in the fusion zone microstructure of the clad specimen. The microstructural characterization shows a homogenous and dense microstructure with a porosity value of less than 1%. The columnar dendrites grew perpendicularly to the substrate was observed in the clad zone microstructure. The average microhardness of the deposited clad was significantly higher than that of the base metal (MS), indicating improved surface properties of the base material. Further, corrosion testing indicates that the clad specimen has significantly higher corrosion resistance than that of the base metal (MS) in a 3.5 wt% NaCl solution.

Investigation on Microstructure, Hardness and Wear Resistance of Electron Beam Wire-Feeding Deposited Inconel 718 Alloy Coatings

The Inconel 718 (IN718) alloy coatings were successfully fabricated using electron beam wire-feeding deposition technology. The macrostructure, microstructure and elemental analysis of the deposited coatings were characterized by OM, SEM and EDS. Moreover, the hardness and wear resistance were also investigated experimentally. The results showed that the cross section of the deposited coatings can be divided into three different regions: clad zone (CZ), fusion zone (FZ) and heat affected zone. Equiaxed dendrites appeared in the CZ while columnar dendrites occurred in the FZ, and discrete fine Laves phase particles were formed under low beam current while continuous coarse Laves phase particles were found under high beam current. The EDS results showed that the degree of Nb segregation in FZ is higher than that in CZ. More importantly, the microstructure coarsened and the degree of Nb segregation increased with the increase of beam current. The deposited coating under the lowest beam current (10 mA) has the highest hardness (263 HV0.2) and the minimum specific wear rate (3.95391 × 10−15 m3/Nm), which is corresponding to the fine microstructure, discrete Laves phase particles and low degree of Nb segregation under low beam current.

Microstructure and properties of Cu-Ti-Ni composite coatings on gray cast iron fabricated by laser cladding

To improve the wear resistance of gray cast iron and the quality of the laser cladding coating, a composite coating was designed and produced using Cu-Ti-Ni blending powder on the surface of gray cast iron by fiber laser cladding system. The phase constituents and microstructure of the composite coating were investigated using X-ray diffraction (XRD) and scanning electron micrograph (SEM). Microhardness and wear resistance of the coatings were evaluated. The experimental results indicated that TiC reinforced composite coating was produced and the matrix of the laser cladding zone composed of alloy γ-Fe, acicular martensite, and α-Cu. Microscale TiC particles were synthesized in the laser melted pool using the graphite phase of the substrate and the titanium atom of the blending powder. The surface properties of gray cast iron was improved by TiC reinforced comppsite coating. The microhardness of the laser cladding zone was approximately 2 to 3 times that of the substrate and the wear resistance of the coating was significantly improved. The wear mechanism of the coating was adhesive wear and abrasive wear because the matrix was soft alloy γ-Fe and α-Cu. The coating could significantly improve the performance of grey cast iron under severe service conditions.

Dissimilar Cladding of Ni–Cr–Mo Superalloy over 316L Austenitic Stainless Steel: Morphologies and Mechanical Properties

The solid solution strengthened Inconel 625, a Ni-based alloy is known for its excellent strength and good corrosion resistance at extreme environments used in thermal plants, boiler tubes, petrochemical industry and power plant. The presence of Cr content (~ 20 wt%) along with Mo-rich, Nb and Fe makes Ni–Cr–Mo–Nb austenitic alloy called as Inconel 625 to achieve excellent corrosion resistance property. Using cold metal arc transfer (CMT) cladding, the metallurgical, mechanical and corrosion properties of Inconel 625 on 316L is evaluated. The process parameters selected includes welding current, torch angle and travel speed with a constant voltage. From the results of microstructural and EDS inferences, the formation of cellular dendritic structure with secondary phases like Laves phase, complex nitrides along with the interdendritic segregation of Mo and Nb as well as microsegregation of Cr, Ni and Fe. In case of Ni–Cr–Mo alloy, Ni and Cr contribute to resistance to corrosion in NaCl environments. The formation of Cr2O3 and the passivation action of the clad zone is due to the presence of Cr. The solid solution effect in Ni–Cr matrix is contributed by the presence of Nb and Mo. Apart from that the strengthening action happens due to the precipitation of Ni3 (Al, Ti, Nb) commonly known as γ′, γ″ and MC carbides confirmed through XRD. Uni-axial tensile tests and Vickers-micro hardness indentation tests were performed on Inconel 625 cladded over 316L. Based on the fractographic results fatigue striations, tear rigdes with river markings, dimples with fibrous structure and cleavages are observed. Unlike other studies, unique type of cuboidal precipitates are seen, which is due to the presence of Ti, which form carbonitrides containing Ti, which are further characterised as NbC. The potentiodynamic polarisation tests is performed on 3.5% NaCl solution. The results suggest that Ni–Cr–Mo alloy protects the substrate from corrosion.

Laser cladding of Inconel 718 with 75Cr3C2 + 25(80Ni20Cr) powder: Statistical modeling and optimization

Laser cladding of Inconel 718 superalloy with 75Cr3C2 + 25(80Ni20Cr) powder was performed with a 400 W pulsed Nd:YAG laser using Response Surface Methodology. Laser frequency, pulse width, and scanning speed were considered as the input variables. The geometry of the deposited beads (width, height, and clad angle), dilution ratio, and hardness were considered as the output responses. It is found that the laser frequency and pulse width have a positive effect on the bead width, clad angle, and dilution ratio but a negative effect on the bead height and hardness. In contrast, the reverse effect is observed for the laser scanning speed. There is an opposite relationship between the hardness value and the dilution ratio. By increasing the dilution ratio, the concentration of chromium carbides in the deposited bead decreases, causing a drop in the hardness, compared to the condition with a low dilution ratio. The process optimization was performed by a simultaneous optimization technique. The laser frequency of 20 Hz, pulse width of 12.9 ms, and laser scanning speed of 5.43 mm/s are found to be the optimum parameters over the ranges investigated in this work. The average hardness value of the optimum sample is approximately 1050 Hv, about 2.5 times the value of the substrate (IN 718 in solution annealed condition). The clad zone of the optimum sample is mainly composed of chromium carbide (Cr7C3) and refined eutectic structure (γ + Cr7C3). The γ + Laves (δ) eutectic structure is formed in the partially melted zone of the optimum sample.

Direct laser cladding of the silicide dispersed titanium aluminide (Ti45Al5Nb0.5Si) composites

The present study concerns development of titanium silicide dispersed titanium aluminide composite with addition of 5 wt.% and 10 wt.% Si in Ti45Al5Nb0.5Si base alloy by direct laser cladding under varied process parameters. Direct laser cladding has been conducted using a high power (3 kW) fiber optic delivered Nd:YAG laser (with a beam diameter of 2 mm) using a 3-axis handling system in a layer by layer fashion to develop a coupon with a dimension of 10 mm × 10 mm × 4 mm. The effect of process parameters (applied power, scan speed and powder feed rate) on the depth and integrity of the clad zone, microstructures and microhardness have been studied in details to optimize process parameters. Addition of Si leads to formation of micro-cracks in the microstructures under varied parameters. There are formations of different silicides (Ti5Si3, Ti7Al5Si12, TiSi2 and TiSi phases) in the microstructure of the base alloy with the presence α2 + γ phase. The microhardness of the clad layer increases with addition of Si. However, optimization of process parameters needs to be undertaken for the formation of defect free microstructure with improved hardness.

A comparative study on wear behaviour of Cr/Mo surface modified grey cast iron

This paper presents laser cladding of grey cast iron with addition of Cr and Mo powder for enhanced wear properties. The laser cladding process was conducted using a Nd:YAG laser system. Sliding wear test were carried out on a linear reciprocating wear testing machine to analyse the wear rate during dry sliding. Based on the metallographic study, graphite phase was eliminated from the clad zone and formed small dendrite structure with fine particles. This phenomenon increased the hardness properties of the cladding surface with a maximum hardness of 945.5 HV0.1. Meanwhile, the wear resistance of cladding surface was improved relative to the as-received grey cast iron with weight loss reduction of more than 96 percent. When Cr-Mo mixture was added, the worn surfaces were moderately smooth with only slight scratches and minimal adhesive attribute because of the formation of carbide phase. The improvement of the grey cast iron surface was due to the change of chemical composition and presence of the hard phase, M2C, M3C2 and M23C6 produced by laser cladding.

The effect of plasma torch weaving on microstructural evolution in multiple-pass plasma-transferred arc Fe-Cr-V-Mo-C coating

Microstructural evolution, hardness and abrasive wear resistance of plasma-transferred arc (PTA) multipass Fe-Cr-V-Mo-C coatings deposited using plasma source weaving has been investigated. As shown, the deposited metal contains structurally different as-deposited clad zone and reheated zone. There are reheated zones formed between the coating beads and between microbeads formed due to weaving mode deposition (WPTA). Both types of zones contain eutectic carbide recrystallization and incomplete melting regions. No high-martensite, low wear resistance high-tempered region inherent to standard multipass PTA deposition has been found. The overall wear resistance of the coating has been improved as compared to the PTA version.

Microstructural Evolution and Phase Transformation in Laser Cladding of Cr and Mo Powder on Grey Cast Iron: Mixture Design of Experiment (DOE)

Laser cladding on grey cast iron at high power processing was investigated for microstructural evolution and phase transformation to enhance surface properties. Cladding was designed using a mixture of DOE with peak power (Pp) and pulse repetition frequency (PRF), and a mixture component of Cr and Mo ratio as factors. Microstructural findings indicated absolute elimination of graphite phase from the clad zone, in conjunction with particles evolution occurrence. Meanwhile, Cr, Mo and Fe phases were detected on the clad surface, along with M-C carbide, retained austenite and MoFe formation. The clad surface with addition of Mo exhibited a high hardness value of 945.5 HV0.1 due to carbide formation. As a result of high peak power penetration into substrate surface, the depth range of clad zone was 53 to 131 µm. From the optimisation, the highest desirability is 82.3 %. Cladding with molybdenum powder addition was found to have produced minimum surface roughness, maximum depth and hardness of 9.14 µm, 110 µm and 891.1 HV0.1, respectively.