High Power Diode Laser Surface Research Articles

Multi-objective optimization of high power diode laser surface hardening process of AISI 410 by means of RSM and desirability approach

In this research, laser surface hardening of AISI 410 was carried out by a high power diode laser based on Response Surface Method (RSM). Laser power, scanning speed, and focal plane position were evaluated as input process changeable while geometry dimensions of hardened zone (i.e., Depth and width of hardness), maximum hardness, Microhardness deviation (MHD) from base material in depth, and ferrite phase percentage in the microstructure were evaluated as process output Results. The effect of input parameters on the response variations were studied by statistical investigation. Results indicated that by increasing the laser power and decreasing other parameters, higher surface hardness with significant penetration, and least ferrite percentage would be reached by means of the desirability function approach. By using experimental tests, validation of optimized results was performed. In this research in the optimum conditions, the maximum hardness, maximum depth of hardness and minimum ferrite percentage were achieved 670 Vickers, 2.2 mm and 0.45%, respectively.

Microstructural and Mechanical Properties Examination of High-Power Diode Laser-Treated R260 Grade Rail Steels Under Different Processing Temperatures

In the present study, high-power diode laser surface treatment was implemented to R260 grade steel with three different processing temperatures (1100 °C, 1200 °C, and 1300 °C) at the laser power of 1750 W and scanning speed of 6 mm/s, in order to identify the effect of various processing temperatures on the mechanical performance. According to the test results, the laser-treated sample at 1300 °C showed much better mechanical performance among the other laser-treated samples. It was found that the laser-treated sample at 1300 °C had about 3 times more surface hardness, a 43 pct increase in yield strength, and a 53 pct increase in toughness value compared to the untreated sample. Microstructural investigations showed that this surface treatment did not only generate a martensitic structure with a certain depth but also provided the formation of a fine pearlitic structure contributing to an increase in the mechanical properties. As a conclusion, it was found that the processing temperature is one of the critical factors affecting the mechanical properties in the laser hardening process. Moreover, the results demonstrated that this treatment method might be an alternative method to enhance the mechanical properties of existing rail steels online without the need for rail disassembly, reducing operational costs.

High power diode laser surface hardening of AISI 4130; statistical modelling and optimization

Laser surface hardening of AISI 4130 carbon steel was conducted with a high power diode laser using Response Surface Methodology. Scanning speed, laser power and focal plane position were considered as the input process variables and cross sectional geometry of the hardened area, average micro-hardness and the ferrite phase percentage were considered as process responses. The effect of parameters on the responses variations were investigated using analysis of variance. Microstructure evaluation of the laser hardened zone was performed using optical and field emission scanning electron microscopy. Results indicated that by increasing the laser power and decreasing the scanning speed and focal plane position, higher surface hardness with more penetration in depth, higher average micro-hardness and minimum ferrite percentage will be achieved. Finally, the process was optimized by desire ability approach based on the applied statistical analyses. Minimum value of percentage of the ferrite and maximum value of the other responses are considered as optimization criteria. The recommended optimized results were validated using the experimental tests. The results show that the hardness of the diode laser hardening process is 3 times of the hardness of the base metal. Laser-overlapping scanning is performed in the optimum setting and effect of overlapping percentage is investigated.

Effect of Graphite Coating on Microstructure and Corrosion Properties of High Power Diode Laser Surface Melting of 7075 Aluminum Alloy

Effect of Graphite Coating on Microstructure and Corrosion Properties of High Power Diode Laser Surface Melting of 7075 Aluminum Alloy

The Effect of Laser Surface Treatment on Structure and Mechanical Properties Aluminium Alloy ENAC-AlMg9

Abstract In this work, the influence of a high power diode laser surface treatment on the structure and properties of aluminium alloy has been determined. The aim of this study was to improve the mechanical and tribological properties of the surface layer of the aluminium alloy by simultaneously melting and feeding tungsten carbide particles into the molten pool. During the process was used high-power diode laser HPDL. In order to remelt the aluminium alloy surface the HPDL laser of 1.8, 2.0 and 2.2 kW laser beam power has been used. The linear laser scan rate of the beam was set 0.5 cm/s. In order to protect the liquid metal during laser treatment was used argon. As a base material was used aluminium alloy ENAC-AlMg9. To improve the surface mechanical and wear properties of the applied aluminium alloy was used biphasic tungsten carbide WC/W2C. The size of alloying powder was in the range 110-210 µm. The ceramic powder was introduced in the remelting zone by a gravity feeder at a constant rate of 8 g/m.

High power diode laser surface melting of SUS 420F steel: investigations on the microstructural, and mechanical properties

This research work deals with studies on the laser surface melting (LSM) of SUS 420F plastic mould steel by a high power diode laser (HPDL). The laser treated samples were investigated by optical microscopy, high resolution scanning electron microscopy (HRSEM) and X-ray diffractometry (XRD), and the hardness profiles of the laser surface melting layers were evaluated by a Vickers hardness tester. The plastic mould steel, on surface melting with HPDL contains columnar dendrite and fine martensite microstructure with residual austenite phases. The microstructure transformed from columnar dendrite to randomly oriented ones, as the power was increased from 2 to 3 kW. XRD phase analysis confirmed the formation of martensite and M23C6 carbide phases at near surface regions of laser treated steel. The high power laser treatment increased the hardness to around 700 HV and wear resistance of the steel was also found to be increased.

Laser Surface Treatment of Hydro and Thermal Power Plant Components and Their Coatings: A Review and Recent Findings

High-power diode laser (HPDL) surface modification of hydro and thermal power plant components is of the utmost importance to minimize their damages occurring due to cavitation erosion, water droplet erosion, and particle erosion (CE, WDE, and PE). Special emphasis is given on the HPDL surface treatment of martensitic and precipitate-hardened stainless steels, Ti6Al4V alloy, plasma ion nitro-carburized layers, high pressure high velocity oxy-fuel and twin-wire arc sprayed coatings. WDE test results of all these materials and coatings in ‘untreated’ and ‘HPDL- treated at 1550 °C’ conditions, up to 8.55 million cycles, are already available. Their WDE testing was further continued up to 10.43 million cycles. The X20Cr13 and X10CrNiMoV1222, the most common martensitic stainless steels used in hydro and thermal power plants, were HPDL surface treated at higher temperature (1650 °C) and their WDE test results were also obtained up to 10.43 million cycles. It is observed that the increased HPDL surface temperature from 1550 to 1650 °C has resulted in significant improvement in their WDE resistances because of increased martensitic (ά) phase at higher temperature. After conducting long-range WDE tests, the correlation of CE, WDE, and PE resistances of these materials and protective coatings with their mechanical properties such as fracture toughness and microhardness product, ultimate resilience, modified resilience, and ultimate modified resilience has been reviewed and discussed. One of the edges of a 500 MW low pressure steam turbine moving blade (X10CrNiMoV1222 stainless steel) was HPDL surface treated at 1550 °C and its radii of curvatures and deflections were measured. These were compared with the data available earlier from a flat rectangular sample of similar composition and identical HPDL surface temperature.

Numerical and experimental study of the temperature field evolution of Mg alloy during high power diode laser surface melting

During the laser surface melting (LSM) of AZ31B Mg alloy, obtaining desired temperature field distribution is essential for production goal and reliable service performance. In this study, a 3D finite element model was developed to analyze the thermal characteristics during the diode laser surface melting of Mg alloy with different process parameters. The simulation visually predicts the great temperature gradient and fast cooling speed during LSM. The microstructure of the fusion zone was observed to validate the accuracy of the simulation. Verification experiment based on infrared temperature measurement (ITM) was applied. By comparing the maximum temperature values, the average heating and cooling rate and the dimension of the melt pool with various laser powers and scanning speed, the simulation results are in good agreement with the experimental measurements.

Influence of the HPDL Surface Treatment of the X40CrMoV5-1 Tool Steel on Wear Resistance

The paper presents the effect of alloying with WC and TaC powders on structure and mechanical properties of the X40CrMoV5-1 steel surface layer using the HPDL (High Power Diode Laser). The metallographic investigations on light microscope show that during alloying the X40CrMoV5-1 hot work tool steel with the WC and TaC powder the obtained run face is characteristic of the high roughness, multiple pores, irregularity, and flashes at the borders. The changes of the surface layers hardness formed as a result of alloying with ceramic powders containing carbides are accompanied with the increased tribological properties. The microstructure of the alloyed layers which were formed on the surface of the investigated hot work steel was examined using optical microscope. The tribological wear relationships using pin-on-disc test were specified for surface layers subject to laser treatment, determining the friction coefficient, and mass loss of the investigated surfaces.

A Comparative Study of High-Power Diode Laser and CO2 Laser Surface Hardening of AISI 1045 Steel

The study investigates laser surface hardening in the AISI 1045 steel using two different types of industrial laser: a high-power diode laser (HPDL) and a CO2 laser, respectively. The effect of process parameters such as beam power, travel speed on structure, case depth, and microhardness was examined. In most cases, a heat-affected zone (HAZ) formed below the surface; a substantial increase in surface hardness was achieved. In addition, big differences were found between the hardened specimens after HPDL surface hardening and CO2 laser surface hardening. For HPDL, depths of the HAZ were almost equal in total HAZ o, without surface melting. For CO2 laser, the depths changed a lot in the HAZ, with surface melting in the center. To better understand the difference of laser hardening results when use these two types of laser, numerical (ANSYS) analysis of the heat conduction involved in the process was also studied. For HPDL method, a rectangular beam spot and uniform energy distribution across the spot were assumed, while for CO2 laser, a circular beam spot and Gaussian energy distribution were assumed. The results showed that the energy distribution variety altered the thermal cycles of the HAZ dramatically. The rectangular HPDL laser beam spot with uniform energy distribution is much more feasible for laser surface hardening.

High-Power Diode Laser-Treated 13Cr4Ni Stainless Steel for Hydro Turbines

The cast martensitic chromium nickel stainless steels such as 13Cr4Ni, 16Cr5Ni, and 17Cr4Ni PH have found wide application in hydro turbines. These steels have adequate corrosion resistance with good mechanical properties because of chromium content of more than 12%. The 13Cr4Ni stainless steel is most widely used among these steels; however, lacks silt, cavitation, and water impingement erosion resistances (SER, CER, and WIER). This article deals with characterizing 13Cr4Ni stainless steel for silt, cavitation, and water impingement erosion; and studying its improved SER, CER, and WIER behavior after high-power diode laser (HPDL) surface treatment. The WIER and CER have improved significantly after laser treatment, whereas there is a marginal improvement in SER. The main reason for improved WIER and CER is due to its increased surface hardness and formation of fine-grained microstructure after HPDL surface treatment. CER and WIER of HPDL-treated 13Cr4Ni stainless steel samples have been evaluated as per ASTM G32-2003 and ASTM G73-1978, respectively; and these were correlated with microstructure and mechanical properties such as ultimate tensile strength, modified ultimate resilience, and microhardness. The erosion damage mechanism, compared on the basis of scanning electron micrographs and mechanical properties, is discussed and reported in this article.

High Power Diode Laser-Treated HP-HVOF and Twin Wire Arc-Sprayed Coatings for Fossil Fuel Power Plants

This article deals with high power diode laser (HPDL) surface modification of twin wire arc-sprayed (TWAS) and high pressure high velocity oxy-fuel (HP-HVOF) coatings to combat solid particle erosion occurring in fossil fuel power plants. To overcome solid particle impact wear above 673 K, Cr3C2-NiCr-, Cr3C2-CoNiCrAlY-, and WC-CrC-Ni-based HVOF coatings are used. WC-CoCr-based HVOF coatings are generally used below 673 K. Twin wire arc (TWA) spraying of Tafa 140 MXC and SHS 7170 cored wires is used for a wide range of applications for a temperature up to 1073 K. Laser surface modification of high chromium stainless steels for steam valve components and LPST blades is carried out regularly. TWA spraying using SHS 7170 cored wire, HP-HVOF coating using WC-CoCr powder, Ti6Al4V alloy, and high chromium stainless steels (X20Cr13, AISI 410, X10CrNiMoV1222, 13Cr4Ni, 17Cr4Ni) were selected in the present study. Using robotically controlled parameters, HPDL surface treatments of TWAS-coated high strength X10CrNiMoV1222 stainless steel and HP-HVOF-coated AISI 410 stainless steel samples were carried out and these were compared with HPDL-treated high chromium stainless steels and titanium alloy for high energy particle impact wear (HEPIW) resistance. The HPDL surface treatment of the coatings has improved the HEPIW resistance manifold. The improvement in HPDL-treated stainless steels and titanium alloys is marginal and it is not comparable with that of HPDL-treated coatings. These coatings were also compared with “as-sprayed” coatings for fracture toughness, microhardness, microstructure, and phase analyses. The HEPIW resistance has a strong relationship with the product of fracture toughness and microhardness of the HPDL-treated HP-HVOF and TWAS SHS 7170 coatings. This development opens up a possibility of using HPDL surface treatments in specialized areas where the problem of HEPIW is very severe. The HEPIW resistance of HPDL-treated high chromium stainless steels and titanium alloys, HPDL-treated TWAS SHS 7170 and HP-HVOF coatings, and their micrographs and X-ray diffraction analysis is reported in this article.

Influence of Laser Power on the Hardening of Ti6Al4V Low-Pressure Steam Turbine Blade Material for Enhancing Water Droplet Erosion Resistance

To overcome water droplet erosion of Ti6Al4V alloy blade material used in low-pressure steam turbine (LPST) of high-rating nuclear and super critical thermal power plants, high-power diode laser (HPDL) surface treatment at two temperatures corresponding to two different power levels was carried out. During incubation as well as under prolonged erosion testing, the HPDL surface treatment of this alloy has enhanced its resistance significantly. This is due to the formation of fine-grained martensitic (ά) phase due to rapid heating and cooling associated with laser treatment. The droplet erosion test results after HPDL surface treatment on this alloy, SEM, XRD analysis, and residual stresses developed due to HPDL surface treatment are given in this paper.

Enhanced Droplet Erosion Resistance of Laser Treated Nano Structured TWAS and Plasma Ion Nitro-Carburized Coatings for High Rating Steam Turbine Components

This article deals with surface modification of twin wire arc sprayed (TWAS) and plasma ion nitro-carburized X10CrNiMoV1222 steel using high power diode laser (HPDL) to overcome water droplet erosion occurring in low pressure steam turbine (LPST) bypass valves and LPST moving blades used in high rating conventional, critical, and super critical thermal power plants. The materials commonly used for high rating steam turbines blading are X10CrNiMoV1222 steel and Ti6Al4V titanium alloy. The HPDL surface treatment on TWAS coated X10CrNiMoV1222 steel as well as on plasma ion nitro-carburized steel has improved water droplet resistance manifolds. This may be due to combination of increased hardness and toughness as well as the formation of fine grained structure due to rapid heating and cooling rates associated with the laser surface treatment. The water droplet erosion test results along with their damage mechanism are reported in this article.

High Power Diode Laser Surface Treatment to Minimize Droplet Erosion of Low Pressure Steam Turbine Moving Blades

This article deals with the high power diode laser (HPDL) surface treatment to overcome water droplet erosion of Low Pressure Steam Turbine (LPST) moving blades used in high rating conventional, critical and super critical thermal power plants. The materials generally used in these steam turbines are titanium alloy (Ti6Al4V), precipitate hardened stainless steel (17Cr-4Ni PH), X20Cr13 and X10CrNiMoV1222 steels. During incubation period as well as under prolonged testing, the HPDL surface treatment of these materials except for 17Cr-4Ni PH steel has enhanced the droplet erosion resistance significantly. This is due to increased hardness and formation of fine-grained martensitic phase due to rapid heating and cooling rates associated with laser treatment. The droplet erosion results of HPDL laser surface treatment of all these materials and their analysis form the main part of the article.

Effect of high power diode laser surface melting on wear resistance of magnesium alloys

In the present work, an attempt has been made to improve the surface hardness and wear properties of magnesium alloys AZ31 and AZ61 through solid solution hardening and refinement of microstructures using a 1.5 kW high power diode laser (HPDL) as a heat generating source. One millimetre thick uniform overlapping melt tracks were produced on Mg alloy samples. Laser-melted samples were subjected to a two-body abrasive wear test using a modified pin-on-disc set up. The hardness and wear resistance of laser-melted samples were found far better than the as-received Mg alloy substrates. Scanning electron microscopy was used to examine microstructure of the laser-melted layers and the worn surface morphology. Fine microstructures were observed with an average grain size of less than 5 μm.

Augmentation of the mechanical and chemical resistance characteristics of an Al 2O 3-based refractory by means of high power diode laser surface treatment

Augmentation of the wear rate and wear life characteristics of an Al 2O 3-based refractory within both normal and corrosive (NaOH and HNO 3) environmental conditions was effected by means of high power diode laser (HPDL) surface treatment. Life assessment testing revealed that the HPDL generated glaze increased the wear life of the Al 2O 3-based refractory by 1.27–13.44 times depending upon the environmental conditions. Such improvements are attributed to the fact that after laser treatment, the microstructure of the Al 2O 3-based refractory was altered from a porous, randomly ordered structure, to a much more dense and consolidated structure that contained fewer cracks and porosities. In a world economy that is increasingly placing more importance on material conservation, a technique of this kind for delaying the unavoidable erosion (wear) and corrosion that materials such as the Al 2O 3-based refractory must face may provide an economically attractive option for contemporary engineers.

Identification of the principal elements governing the wettability characteristics of ordinary Portland cement following high power diode laser surface treatment

The elements governing modifications to the wettability characteristics of ordinary Portland cement (OPC) following high power diode laser (HPDL) surface treatment have been identified. Changes in the contact angle, θ, and hence the wettability characteristics of the OPC after HPDL treatment were attributed to: reductions in the surface roughness of the OPC; the increase in the surface O 2 content of the ceramic and the increase in the polar component of the surface energy, γ sv p. What is more, the degree of influence exerted by each element has been qualitatively ascertained and was found to differ markedly. Surface energy, by way of microstructural changes, was found to be by far the most predominant element governing the wetting characteristics of the OPC. To a much lesser extent, surface O 2 content, by way of process gas, was also seen to influence to a changes in the wettability characteristics of the OPC, whilst surface roughness was found to play a minor role in inducing changes in the wettability characteristics.

Influence of high power diode laser surface melting on the pitting corrosion resistance of type 316L stainless steel

High Power Diode Lasers (HPDL) are becoming more and more attractive for industrial materials processing because of their high efficiency, low running costs, small sizes and low weight. Surface melting experiments have been carried out on 316L steel with a 1 kW HPDL, with application to modify its pitting corrosion resistance in NaCl 0.05 M. Surface modifications have been investigated with optical microscopy for the microstructure, microprobe analysis for the chemical content and X Ray Diffraction for phase transformations and residual stresses. Heat conduction characteristics, analysed with a 2D Finite element code, have driven to a 28% calculated absorption of the laser light generating nearly 400 μm melted depth. A refinement and homogenization of structure together with δ-ferrite transformation and the dissolution of inclusions was found in the melted thickness, driving to enhanced pitting resistance (nearly + 0.2 V on the pitting potential values, and factor 2 decrease of the passive current density). This pitting resistance, investigated at different depths below the surface, was found to be little affected by the δ ferrite content (6% estimated value), and the fineness of the microstructure, but depreciated by the surface state without post-polishing. Therefore, it is believed that localized corrosion improvements can be mainly attributed to the dissolution of Al-base and Mn-base detrimental inclusions, despite the generation of up to 6% δ ferrite susceptible to drive to enhanced galvanic couplings with γ phase.

A laser-based technique for the coating of mild steel with a vitreous enamel

Marked changes in the wettability characteristics of EN8 mild steel were observed after high-power diode laser (HPDL) surface treatment of the metal. The morphological, microstructural and wetting characteristics of the steel were determined using optical microscopy, scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS) and wetting experiments by the sessile drop technique. Improvements in the wetting action of the mild steel after HPDL surface treatment were identified as being the result of: HPDL-induced melting of the mild steel surface, which brought about a reduction of the surface roughness; and a small increase in the polar component of the surface energy and an increase in the surface O 2 content of the mild steel resulting from HPDL treatment. This work has demonstrated that the use of HPDL radiation to alter the wetting characteristics of mild steel in order to facilitate improved enamelling is a real possibility.