Clad Profile Research Articles

Numerical and experimental investigation for the cladding of AISI 304 stainless steel on mild steel substrate using Gas Metal Arc Welding

In the present study, Gas Metal Arc Welding (GMAW) is used to deposit AISI 304 stainless steel layer on the mild steel substrate. The cladding parameters like welding voltage and feed rate have been varied to identify the deposited AISI 304 stainless steel bead profile and factors affecting the bead deposition on the mild steel substrate. Microscopic and EDS analysis confirms the successful deposition of the stainless steel layer on the mild steel substrate. The GMAW parameters like welding voltage and wire feed rate (WFR) govern the AISI 304 clad bead quality like clad profile, heat affected zone (HAZ), and clad penetration. A numerical model has also been developed using a double ellipsoidal heat source to identify the effect of welding parameters on the clad bead. The developed numerical model identifies the temperature distribution along with the clad bead profile and the model is identical with the experimental results. The experimental results showed that a non-uniform weld bead formation has been observed at lower voltage (14 V) and low WFR (3 m/min). The clad bead quality has improved with an increase in the welding voltage (16 V & 18 V) and wire feed rate (5 m/min & 7 m/min). However, cladding at a high wire feed rate (7 m/min) results in low dilution of the clad material with the substrate.

Process Variable Optimization of Cold Metal Transfer Technique in Cladding of Stellite-6 on AISI 316 L Alloy Using Grey Relational Analysis (GRA)

In this work, an attempt was made to identify the optimised parameter combination in cold metal transfer (CMT) cladding process of AISI 316 L austenitic stainless steel. cladding process was carried out using stellite 6 filler wire. Experiments were carried out based on L31 central composite design (CCD). Cladding was done with current, Voltage, torch angle and travel speed as input parameters. Quality of the clad was analysed by measuring depth of penetration, weld area, hardness of the clad surface, corrosion rate and clad interface thickness. Grey relation analysis was used to identify the optimised parameter combination. Trial number 18 was identified as the optimised parameter combination. The optimised input parameters are Welding Current 200 Amps, Voltage 19 V, Torch Angle 70⁰ and Welding Speed 150 m/min. ANOVA was used to identify the most influencing parameters on the overall multi-objective function and it was understood that the combined effect of torch angle, travel speed had a significant influence on the clad quality. Further investigation was carried out through an optimised set of parameters. The cladding experiment was conducted and their surface was investigated through clad profile, hardness of the cladded area, interface thickness of cladding region and corrosion rate.

Parametric investigation and optimization for CO2 laser cladding of AlFeCoCrNiCu powder on AISI 316

Abstract The purpose of the current investigation is to analyze the effect of the operating parameters of laser-assisted cladding process on clad height, clad depth, clad width and the percentage dilution in a cladding of AlFeCuCrCoNi high-entropy powder on SS-316 through CO2 laser and to optimize the cladding process parameters for optimum dilution. The experiments were designed by the full factorial method and analyzed by ANOVA. The analysis results indicate that dilution is most influenced by scanning speed followed by the powder feed rate. The outcomes of the single clad profile in terms of dilution, microhardness, composition and the microstructures produced in various cladding conditions are investigated briefly, and through which the optimum set of laser cladding operating parameters for maximum hardness of the clad material is determined. The optimum cladding conditions in the experimental range were obtained at 4 g/min powder feeding rate, 500 mm/min laser scanning speed and 1.1 kW laser beam power through multi-response optimization. Furthermore, the multi-track coating with 60% overlapping ratio was deposited using optimized parameters. The wear behavior of multi-track coating was determined using pin on disk wear apparatus with applied load of 20 N, sliding speed of 300 RPM and test duration of 15 min. The pin on disk wear test results indicates that the friction coefficient of SS-316 is larger than that of high-entropy alloy cladded SS-316. The wear resistivity of SS-316 improved by 40.35% after laser-assisted high-entropy alloy coating, which confirms that the laser cladding layer plays an essential role in enhancing the wear resistance capability of austenite steel.

Implementation of fluorophoshate laser glass for short length active fiber at 1.5 μm

We successfully fabricated a short-length active fiber based on fluorophosphate (FP) laser glass by the rod-in-tube technique and fiber drawing process. The base FP laser glass composition, 20Al(PO3)3-40BaF2-40SrF2 was used for making glass fiber with appropriate core and clad profiles. The physical, thermal, optical, and spectroscopic properties of core and clad materials were optimized in order to implement FP laser glass for active glass fiber fabrication. The difference of refractive index and the glass transition temperature between core and clad glass ingots was obtained to be close to 0.004 and 6 °C, respectively. The spectroscopic properties of FP laser glasses were also derived. The gain and gain coefficient of the indigenously fabricated glass fiber were measured to be 10.29 dB and 0.60 dB/cm at 1550 nm from a 17 cm bare fiber, respectively. The results direct that the short length active fiber based on FP laser glass could be useful for compact all-optical fiber amplifier at 1.5 μm.

A Simple and Accurate 3D Numerical Model for Laser Cladding

ABSTRACTA simple numerical model has been proposed for laser cladding. The model does not involve complex techniques such as cell addition, moving mesh, or prescribing a clad profile with a certain polynomial function. Instead, a mass function has been introduced to register the clad mass deposition on substrate, and from which the clad-track height can be estimated. The model takes several operational parameters, laser power, laser-head speed, and clad powder feeding rate, into consideration and predicts clad-track geometry, dilution, and substrate temperature. Experiments using two different combinations of substrate and clad powder materials to lay single and multiple clad tracks were conducted to provide data for model validation. The results show that the present model returns good agreement with experimental clad profiles for single and multiple tracks.

Material and residual stress considerations associated with the autofrettage of weld clad components

A fatigue-resistant cladding concept confirms the presence of compressive residual stresses in a cylinder weld clad with 17–4 PH stainless steel while tensile residual stresses exist in an Inconel 625 clad layer. In this study, autofrettage of an Inconel 625 thick-walled clad cylinder is investigated with modified residual stress distributions obtained indicating that tensile residual stresses throughout the clad layer are transformed to compressive in nature, discontinuity stresses at the clad/substrate interface are almost entirely eliminated and compressive residual stresses exist to a depth of around 18 mm. An alternative clad material, 17–4 PH stainless steel, is investigated resulting in compressive residual stresses in the clad layer without the need for autofrettage. The complexity of modelling a martensitic stainless steel is discussed and sensitivity studies undertaken to illustrate the influence of coefficient of thermal expansion on resulting residual stresses. Strain hardening effects and the assumption of an idealised interface are discussed. Contour method measurements prove that discontinuity stresses are reduced in reality due to alloying and diffusion effects, highlighting also the need for further characterisation of 17–4 PH. Additional considerations such as the weld clad profile and process parameters are briefly discussed.

Effects of pulse duration and overlapping factor on melting ratio in preplaced pulsed Nd:YAG laser cladding

Melting ratio is known as a suitable factor to illustrate the effects of process parameters on the clad profile in order to provide a proper process design. However, the definition of melting ratio based on continuous irradiation of energy does not accommodate for pulse parameters. Hence, in order to study the effects of pulse parameters, such as pulse duration and overlapping factor, the definition of melting ratio is restated for pulsed laser process based on energy density concept. Carbon steel was cladded with Stellite 6 by scanning a 400W pulsed Nd:YAG laser over a preplaced layer of powder paste. The results show that the trends of clad profiles variations can be explained using the restated definition. The results also show two different ranges for the effects of pulse duration and overlapping factor on melting ratio.

Numerical Simulation of Multi-Track Laser Cladding Process

Multi-track laser cladding is necessary in the forming of parts. The overlap between neighbor tracks plays an important role, which determines the quality and surface smoothness of the clad layer. In this paper, numerical simulation of the multi-track laser cladding process is studied. The heat source of laser spot is applied by updating the profile of clad region and the location of the moving laser spot. The clad profile of overlapped track was obtained, from which the surface roughness was analyzed by the variation of overlap ratio. Meanwhile, experiments were carried out to evaluate the effect of overlap ratio. The simulated and the experimental results are in good agreement; both show that there is an optimal overlap ratio to achieve best surface roughness.

Laser Clad Geometry: Experimental Observation and Geometric Modeling

In this paper, a new analytical method of laser clad geometric simulation was developed. The effects of laser process parameters such as laser power, scanning speed, and powder feed rate on estimating clad geometry were investigated in this approach. A series of cladding was prepared by 1 kW diode pumping solid-state laser, to characterize the cross-section image of the clad by optical microscope. The clad profile was fitted by pitch arc and line in AutoCAD, with results displaying the arc-like upper profile of the clad. The theoretical results are discussed and compared with experimental data. The simulation based on the mass conservation is capable of predicting the clad width and depth with reasonable accuracy at medium powder feed rate.

Vision-based clad height measurement

The laser deposition process is useful for part creation, repair, and hard facing. To maintain consistent clad height in the presence of process uncertainties measurement and control is required. This work presents a vision-based clad height measurement technique that utilizes a CCD camera and a line laser to measure the complete clad profile. Unique line detection and spur trimming algorithms are presented that extract measurement data efficiently. The effectiveness of the measurement approach is validated through examples.

Formation of cross-sectional profile of a clad bead in coaxial laser cladding

In order to determine a cross-sectional profile of a clad bead in coaxial laser cladding, its formation mechanism is investigated theoretically and experimentally. In laser cladding, every point at the back edge of a melt pool is contributed to a cross-sectional profile of the clad bead to be formed, and points at the same pool edge but on different cross sections are located at different cross-sectional profiles of the clad bead. A cross-sectional profile of a clad bead is composed of points of intersection between the cross section and a series of pool edges. Model of the cross-sectional clad profile in single-pass coaxial laser cladding is developed. A 500 W CO 2 laser is used in the experiment. The experimental result agrees well with the calculated cross-sectional clad profile.

Design considerations of depressed clad W-shaped single mode dispersion compensating fibers

Dispersion compensating fibers (DCFs) are being widely used as dispersion compensation techniques because of its superior characteristics. This work reports the theoretical modelling of a single mode DCF having W-shaped shallow as well as deeply depressed clad profile. The DCFs have been designed and optimized by suitable adjusting different fiber parameters such as, central relative index difference (Δ+), inner core radius (a), depression depth parameter (ρ), normalized end position of the depressed clad (p), etc. at a given spot size (W¯). The figure of merit (FOM) characteristics including the bend loss as well as other losses associated with fiber manufacturing technique have been thoroughly investigated. Performances of these DCFs for recent wavelength division multiplexing (WDM) transmission system have also been discussed. By adjusting different fiber parameters, the effective core area (Aeff) of the above DCFs can be controlled to minimize the effect of non-linearities on them.

Study on cross-section clad profile in coaxial single-pass cladding with a low-power laser

In this paper, a model of cross-section clad profile on the substrate in coaxial single-pass cladding with a low-power laser was studied. The static model of powder mass concentration distribution at cold-stream conditions was defined as a Gaussian function. In coaxial single-pass cladding with a low-power laser, since the influence of surface tension, gravity and gas flow on the clad bead could be neglected, the cross-section profile of the clad bead deposited by a low-power laser on the substrate was dominated by the powder concentration at each point on the pool and the time when the material was liquid at this point. The height of each point on the cross-section clad profile was defined as a definite integration of a Gaussian function from the moment at which the melt pool was just arriving at the point to the moment at which the point left the melt pool. In the presented experiment, powder of Steel 63 (at 0.63 wt% C) was deposited on a substrate of Steel 20 (at 0.20 wt% C) at the laser power of 135 W. The experimental results testified the model.

Solidification model of laser cladding with wire feeding technique

The object of this study is to investigate the solidification problem in laser cladding with the wire feeding technique. The solidification phenomenon of laser cladding was analyzed by numerical simulation and experimental visualization. Good agreement has been obtained for 304 stainless steel wires cladding on round tubes and it transpires that there were three basic modes of clad profiles: thinning, thickening, and wavering of the clad thickness at different velocity settings between the feeding wire and the substrate in laser wire cladding.

Modelling the geometry of a moving laser melt pool and deposition track via energy and mass balances

The additive manufacturing technique of laser direct metal deposition allows multiple tracks of full density metallic material to be built to form complex parts for rapid tooling and manufacture. Practical results and theoretical models have shown that the geometries of the tracks are governed by multiple factors. Original work with single layer cladding identified three basic clad profiles but, so far, models of multiple layer, powder-feed deposition have been based on only two of them. At higher powder mass flow rates, experimental results have shown that a layer's width can become greater than the melt pool width at the substrate surface, but previous analytical models have not been able to accommodate this. In this paper, a model based on this third profile is established and experimentally verified. The model concentrates on mathematical analysis of the melt pool and establishes mass and energy balances based on one-dimensional heat conduction to the substrate. Deposition track limits are considered as arcs of circles rather than of ellipses, as used in most established models, reflecting the dominance of surface tension forces in the melt pool, and expressions for elongation of the melt pool with increasing traverse speed are incorporated. Trends in layer width and height with major process parameters are captured and predicted layer dimensions correspond well to the experimental values.

Numerical finite element investigation on laser cladding treatment of ring geometries

A laser cladding treatment using powder blown (single track) on a ring part was analyzed adopting a numerical approach, in particular the analyses of both the temperature and the stress distributions in the laser cladding process were performed through a 3D thermo-mechanical finite element (FE) model (ABAQUS/Standard). The thermal FE model was calibrated using the measured clad profile and melt pool size in the substrate; experiments were performed with a 6kW CO2 laser beam using an Al–Si alloy as substrate and a Cu-based alloy as cladding material. The aim of the thermal analysis was determining thermal cycles, variations of the dilution and of the melt pool shape during the process. The mechanical FE model allowed evaluating stress and strain distributions at the end of the treatment. All of these variables were analyzed at the clad–substrate interface as a function of processing parameters (like laser beam power, clad thickness, processing speed), boundary conditions and geometry of the treated zone.

In-time motion adjustment in laser cladding manufacturing process for improving dimensional accuracy and surface finish of the formed part

This paper presents in-time motion adjustment in laser cladding manufacturing process as a means to improve dimensional accuracy and surface finish of the built part. Defects occurring during laser cladding degrade the part quality such as dimensional accuracy and surface finish. In this paper, in-time motion adjustment strategy was presented to remedy and eliminate defects occurring during laser cladding to improve the dimensional accuracy and surface finish. Based on the relationship between the motion of laser head relative to the growing part and other parameters in effects on clad profile, the laser traverse speed, stand-off distance and laser approach orientation to the existing clad layer were adjusted by instructions from a close-loop control system in real time to remedy and eliminate defects. The results of the experiments verified the effects of in-time motion adjustment on dimensional accuracy and surface finish.

Clad profiles in edge welding using a coaxial powder filler nozzle

The powder catchment and clad profile of the edge welding were investigated by experimental and numerical approaches in this study. The clad profile on the edges joined by a coaxial powder filler nozzle with a CO 2 laser was measured and compared with the powder concentration mode, which was confirmed by powder flow visualization and numerical computations. In the numerical simulation of an impinging jet of gas-powder flow on an edge joint, the powder concentration distributed on a V groove joined by two plates was solved by FLUENT software. Based on the Gaussian mode of the powder distribution in the jet flow, a simplified mode function was proposed to estimate the clad profiles in the edge joint. Cladding experiments were performed for mild steel substrates with thicknesses of 2 and 6 mm under 1 kW CO 2 laser irradiation for 304L stainless steel powder. The results show that the concave clad profiles were generated at large incline angles and the powder catchment efficiency might increase with the joint angle and substrate thickness. Based on the analytical results of the cold powder streams impinging on the edge joint, the similarity between the clad profile and the powder concentration in the edge joint is retained only at small incline angles for thin substrates. Due to the heating effects of laser beam spot and the powder re-distribution inside the edge joint, the deviation of the clad profile between the computation and experiment is increased with the incline angle and substrate thickness.

Coaxial laser cladding on an inclined substrate

This paper describes an experimental and theoretical study of the cladding mode of coaxial laser cladding on an inclined substrate. Based on the image analysis of the powder stream and clad profile measurements in coaxial laser cladding, it was found that irregular clad profiles always formed on an inclined surface and the location of the peak profile shifted away from the clad center. This phenomenon is caused by uneven distributions of powder concentration and laser beam intensity. A modified Gaussian mode for powder stream and laser beam was proposed to estimate the clad profiles on an inclined plane under laser beam irradiation. The effects of the inclined steel substrate on the CO 2 laser beam absorption and stainless-steel powder catchment were examined experimentally. The results show that both the laser absorption and the powder catchment on the mild steel decrease with increasing the cladding angle. From the analysis of laser beam mode, the clad width is equivalent to the beam spot size on the inclined substrate. However, the clad height correlates well with the distribution of the powder concentration. The results show that the Gaussian cladding mode could be adopted in various laser cladding applications such as rapid prototyping and butt welding to predict the clad profiles precisely.

An in-process method for the inverse estimation of the powder catchment efficiency during laser cladding

An estimation of the heat loss by conduction can be obtained from measurements of the surface temperature and an overall heat balance at the clad laser interaction zone. Through an inverse calculation of the boundary temperature from observed surface temperatures the powder catchment efficiency can be estimated along with the variation in the clad height expected during laser cladding. This method shows a possible way to monitor and control the clad height and profile as required by near net shape manufacturing methods based on laser cladding.