Effect Of Laser Heat Treatment Research Articles

The Effect of Laser Heat Treatment and Severe Shot Peening on Laser Powder Bed Fusion Manufactured AISI 316L Stainless Steel

In this study the effect of laser heat treatment (LHT) and severe shot peening (SSP) on laser powder bed fusion manufactured AISI 316L stainless steel is investigated. The effect of LHT and SSP on the hardness of the surface of the PBF-LB 316L is studied performing microhardness measurements. Microstructure is evaluated in the EBSD investigation. The residual stresses will be measured to determine the influence of LHT and SSP. The effects of LHT and SSP on tensile and bending fatigue strength will be evaluated. LHT altered the microstructure 200 µm from the surface. The grain structure on the surface was more ordered and no substructure or local strains were present. Finer grain features adjacent to the sample surface were found, which are most likely caused by effective recrystallization and fast cooling. The grain morphology was left relatively unchanged when SSP was applied on LHT surface. However, local deformation has occurred on the surface, and clear orientation gradient within grains is seen. LHT had no effect on the hardness. SSP increased the surface hardness by 205%. LHT decreased the yield or tensile strength of the PBF-LB 316L. Residual stress measurements showed that SSP induced a high compressive stress in the PBF-LB 316L. LHT and SSP significantly improved the fatigue strength of the PBF-LB manufactured 316L.

Effect of Laser Heat Treatment on Mechanical Property of NiW/Ni Coating Electrodeposited on Copper Substrate

Effect of Laser Heat Treatment on Mechanical Property of NiW/Ni Coating Electrodeposited on Copper Substrate

Effect of laser heat treatment on AlxTi1-xN-based PVD coatings, deposited on carbon and tool steel substrates

This paper highlights the effect of laser heat treatment on the adhesion and sliding wear of physical vapour deposited (PVD) multilayer AlxTi1-xN and nanocomposite AlxTi1-xN/α-Si3N4 coatings on carbon (C45E, preliminarily bulk hardened) and tool steel (Vanadis® 6, preliminarily bulk hardened and tempered), as well as substrate steel microstructure and hardness. The hardened zone in carbon steel generally comprises martensite and retained austenite. The hardened zone in tool steel contains martensite and retained austenite, as well as M7C3 (M = Fe, Cr) and MC (M = Fe, V) carbides. Laser heat treatment increased the average surface hardness of the carbon steel by 1.5–3.1 times and that of the tool steel by 1.1–1.2 times. The critical adhesion loads Lc1 and Lc2 enlarged by 1.22.6 times and by 1.2–1.3 times, respectively, in the case of the coatings deposited on the carbon steel. However, only slightly positive or no changes in the critical adhesion loads were observed for the tool steel case. The scratch crack propagation resistance (CPRs) of the coatings increased by 1.1–4.8 times, being more pronounced for the carbon steel substrate. The improvement of adhesion was assumed to be the result of the increased hardness (H) to Young's modulus (E) H/E and H3/E2 ratios of the substrate steel. Wear resistance of the coatings improved by 1.3–1.7 times. Scuffing and surface fatigue wear were the principle wear mechanisms in all the cases. However, the first mechanism was more remarkable for laser heat treated samples, and the second for the samples that remained untreated by laser. Apart from the above-mentioned increment of H/E and H3/E2 ratios, the improvement of wear resistance was explained by the increased CPRs values of the coatings and by the presumed precipitation of the AlN phase within them.

Effect of Laser Heat Treatment on the Mechanical Performance and Microstructural Evolution of AISI 1045 Steel-2017-T4 Aluminum Alloy Joints during Rotary Friction Welding

This paper evaluates the influence of laser power on the rotary friction welding (RFW) process to improve the mechanical performance and microstructural evolution of AISI 1045 steel and 2017-T4 aluminum alloy joints. As part of this evaluation, the absolute chemical determination of these materials was precisely measured using a GDOES bulk analysis. The application of laser power during friction welding is known as laser-assisted friction welding. To evaluate the effect of the energy from the laser on the rotary joining process of steel-aluminum, a laser-assisted rotary friction welding process was set up, and a design of experiments (DOE) applied. First, a DOE consisting of two factors at two levels was used to evaluate the effect of friction pressure and rotational speed on the hardness and tensile strength of the weldment. Then, a mixed DOE of three factors at two and three levels was implemented to investigate the effect laser heat treatment has on the process. It was concluded that the application of a laser heat treatment plays a significant role in the resulting mechanical performance and microstructural evolution of RFW steel-aluminum joints. Increasing both the ultimate tensile strength and the thickness of the Al(Fe, Cu) interface reaction layer between the joined materials.

Effect of Laser Strengthening on Electrochemical Corrosion of AA6082 Aluminum Alloy

In this study, the surface of 6082 aluminum alloy was machined by laser heat treatment, and the microstructure and properties of the affected zone of laser surface were discussed by scanning electron microscope (SEM). The experimental results show that the laser treatment has an obvious second phase fine grain strengthening effect on the surface of aluminum alloy. The local hardness of the surface laser action zone has been improved obviously. Combined with the polarization curve data and microscopic corrosion morphology, with the addition of laser, the corrosion resistance mechanism of aluminum alloy has been well optimized, and the number and continuity of pitting pits on the surface of aluminum alloy have been restrained. The intergranular corrosion and the maximum corrosion depth behavior decreased under the corrosion of Cl−. The comprehensive properties of aluminum alloy surface have been effectively optimized under the action of laser heat treatment.the effect of laser heat treatment on the corrosion resistance and the surface mechanical properties of AA6082 aluminum alloy was investigated.

Effect of Laser Heat-Treatment and Laser Nitriding on the Microstructural Evolutions and Wear Behaviors of AISI P21 Mold Steel

Laser heat-treatment and laser nitriding were conducted on an AISI P21 mold steel using a high-power diode laser with laser energy densities of 90 and 1125 J/mm2, respectively. No change in surface hardness was observed after laser heat-treatment. In contrast, a relatively larger surface hardness was measured after laser nitriding (i.e., 536 HV) compared with that of the base metal (i.e., 409 HV). The TEM and electron energy loss spectroscopy (EELS) analyses revealed that laser nitriding induced to develop AlN precipitates up to a depth of 15 μm from the surface, resulting in surface hardening. The laser-nitrided P21 exhibited a superior wear resistance compared with that of the base metal and laser heat-treated P21 in the pin-on-disk tribotests. After 100 m of a sliding distance of the pin-on-disk test, the total wear loss of the base metal was measured to be 0.74 mm3, and it decreased to 0.60 mm3 for the laser-nitrided P21. The base metal and laser heat-treated P21 showed similar wear behaviors. The larger wear resistance of the laser-nitrided P21 was attributed to the AlN precipitate-induced surface hardening.

Effect of laser heat treatment on structure and wear resistance of cobalt stellite

The structure and wear resistance of Stellite 6 alloy were studied before and after laser heat treatment. A significant refinement of the microstructure after the heat treatment is noted, the hardness the alloy changed slightly. An increase of wear resistance in shock-abrasive wear at angles of attack of 60-90° as well as metal-to-metal wear with presence of an abrasive layer is shown.

Electrochemical assessment of laser heat treatment of an Al–Zn–Mg–Cu alloy

AbstractThe effect of laser heat treatment on the corrosion properties of the 7075 aluminum alloy was studied electrochemically. Laser retrogression and re‐aging (LRRA) is proposed to replace the retrogression treatment of retrogression and re‐aging. Transmission electron microscopy was used to analyze the microstructure of the alloy. The corrosion of the alloy treated using different LRRA parameters was analyzed by scanning electron microscopy. Using the polarization and electrochemical impedance spectroscopy measurements, it was concluded that the best corrosion resistance was obtained by the alloy treated at 2 mm/s with a laser power of 650 W. The spacing between the precipitate‐free zone and grain boundary precipitates increased. It is proved that the laser process can effectively improve the corrosion resistance of the 7075 alloy.

Effect of laser heat treatment on bending property of laser welded joints of low-alloy ultra-high strength steel

This paper investigates the effect of laser heat treatment on the bending property of low-alloy ultrahigh strength steel laser-welded joints. A laser rectangular spot is used for local heat treatment. The results indicate that the back bending angle of joints can be improved from 30° to over 90° with a joint efficiency of 76%. With the increase of laser power and scanning times and the decrease of scanning speed, the heat treatment temperature at the back of the joint increases gradually. The peak temperature under different parameters changes from 450 to 700 °C, at which tempering takes place. This is consistent with the microstructural evolution from original lath martensite of weld metal and heat-affected zone to tempered martensite after laser heat treatment. The hardness between weld and softened zone is similar under the same parameters. Analysis of variance reveals that the hardness is mainly influenced by the peak temperature instead of heating time. The weld hardness decreases gradually with the increase of the peak temperature, and hardness less than 35.0 HRC is obtained when that temperature is over 600 °C. The weld hardness is closely related with the bending property of joints. When the hardness is less than 35.0 HRC, a bending angle over 90° can be achieved. This is because laser tempering makes the hardness of joints uniform, consequently improving the bending performance of the joints.

Effect of Laser Heat Treatment on the Microstructure and Properties of Alloy 800H

The effects of laser heat treatment on the microstructure and properties of alloy 800H were investigated. The fracture morphology, elemental changes, and phase composition of the specimens were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffractometry (XRD). The results show that the long-lasting life of the specimen after laser heat treatment increased by 28.6%, and the elongation after fracture increased by 20.7%. The macroscopic morphology of the fracture specimen exhibited obvious ductile fracture morphology, and the changes in the elemental content and grain size significantly affected the ductility and toughness of the alloy. This study has certain guiding significance for the optimization of the heat treatment process of this type of alloy.

Effect of Laser Heat-treatment on WC-CoFe Coated Surface by HVOF

The microstructure, hardness, and wear behaviors of a High Velocity Oxygen Fuel(HVOF) sprayed WC-CoFe coating are comparatively investigated before and after laser heat treatments of the coating surface. During the spraying, the binder metal is melted and a small portion of WC is decomposed to W2C. A porous coating is formed by evolution of carbon oxide gases formed by the reaction of the free carbon and the sprayed oxygen gas. The laser heat treatment eliminates the porosity and provides a more densified microstructure. After laser heat treatment, the porosity in the coating layer decreases from 1.7% to 1.2 and the coating thickness decreases from 150 μm to 100 μm. The surface hardness increases from 1440 Hv to 1117 Hv. In the wear test, the friction coefficient of coating decreases from 0.45 to 0.32 and the wear resistance is improved by the laser heat treatment. The improvement is likely due to the formation of oxide tribofilms.

Effects of laser heat treatment combined with ultrasonic impact treatment on the surface topography and hardness of carbon steel AISI 1045

The surface layers of medium-carbon steel AISI 1045 were hardened by laser heat treatment (LHT) and by ultrasonic impact treatment (UIT) applied separately and in different sequences. The advantages of the two latter combined laser-ultrasonic hardening and finishing methods (the LHT + UIT and UIT + LHT combined treatments) are also analyzed in this work. The laser transformation hardening process was implemented using a 1 kW solid-state fiber laser with scanning optics and a proportional integral derivative (PID) closed-loop temperature control. The ultrasonic strain hardening process was carried out by means of a 0.3 kW ultrasonic generator and an ultrasonic oscillatory system, which contained a piezoceramic transducer, step-like horn and the impact head with seven cylindrical pins. The single-path processes were studied. The separately applied LHT and UIT process were firstly analyzed using a response surface method (RSM) and the analysis of variance (ANOVA). The effects of the heating temperature (1050–1300 °C) and the specimen feed rate (40–140 mm/min) used at the LHT process on the features of the hardened zone and surface hardness/microhardness of subsurface layer were assessed. The effects of the vibration amplitude of ultrasonic horn (15–18 μm) and treatment duration (60–240 s) at UIT on the surface roughness/waviness and hardness were also investigated. The experimental plan is based on a miscellaneous design matrix method. The quadratic regression equations for predicting the studied output parameters were developed and the optimum regimes of the LHT and UIT processes were determined based on the highest surface hardness and minimum roughness/waviness. Then, the influences of the combined treatments on the surface topography and hardness were analyzed and compared to those of single LHT and single UIT processes. Results show that the combined treatments provide more than triple increase in the surface hardness in comparison with that of the initial state, as well as formation a regular microrelief with minimum surface roughness.

Microstructure and selected properties of Monel 400 alloy after laser heat treatment and laser boriding using diode laser

This study concentrates on describing effects of laser heat treatment of Monel 400 and laser alloying its surface with boron. Surfaces without and with initial boron layers of two different thicknesses (100 and 200 μm) were processed using diode laser. Laser beam power density was constant and equal to 178.3 kW/cm2. To determine the influence of laser beam scanning velocity on final properties of treated surfaces, laser beam scanning velocity was set on four different values: 5, 25, 50, and 75 m/min. Microstructures of pure Monel 400 and Monel 400 alloyed with 100 μm boron content are composed of dendrites. Areas laser alloyed with 200 μm boron layer contain mainly nickel borides. Boron addition in Monel 400 surface results in microhardness increase in which the level depends on boron content and the laser beam scanning velocity. Increasing the thickness of initial boron layer and speeding up the laser beam lead to obtain higher microhardness. On the other hand, areas laser alloyed with 200 μm boron layer using laser beam scanning velocity equal to 75 m/min contain deep cracks which propagate from the surface through the produced layer. Furthermore, it was found that the depths of laser heat-treated areas depend significantly on the boron content. As the result of differences in thermal properties between Monel 400 and boron, depth of re-melted zones in some conditions does not lower with increasing laser beam scanning velocity.

Modelling of the effects of laser modification of gas-nitrided layer

Purpose: The effects of laser processing parameters on the dimensions of simple laser tracks, produced on the previously nitrided layer, were analysed. Design/methodology/approach: Gas nitriding is one of the most commonly used thermochemical treatment, resulting in many advantageous properties: high hardness, enhanced corrosion resistance, improved wear resistance and fatigue strength. However, an unfavourable increase in the thickness of compound zone (e + g’) close to the surface was observed after conventional gas nitriding. This was the reason for undesirable embrittlement and flaking of the layer. Therefore, a controlled gas nitriding was intensively developed, reducing the percentage of the most brittle e (Fe2-3N) iron nitrides. In this study, the hybrid surface layer was produced. The controlled gas-nitriding was followed by laser heat treatment (LHT). Laser modification was carried out using various laser beam powers and scanning rates. The dimensions of laser tracks (i.e. depths and widths of re-melted zone and heat-affected zone) were measured. Numerical methods were used in order to formulate a mathematical model. Findings: Laser processing parameters (laser beam power and scanning rate) influenced the microstructure obtained. The microstructure of laser modified nitrided steel with re-melting consisted of re-melted zone (MZ), heat-affected zone (HAZ), nitrided layer without visible effects of laser treatment and the substrate. The use of laser beam power of 0.26 kW resulted in only a partial re-melting of the compound zone. The two characteristic values of laser beam power were estimated. P0MZ corresponded to the laser beam power at which the re-melted zone disappeared (i.e. width and depth of MZ were equal to 0). P0HAZ was a value of laser beam power at which the effects of laser irradiation were invisible in microstructure (i.e. width and depth of HAZ were equal to 0). The model was proposed in order to predict the effects of LHT on microstructure. Research limitations/implications: The presented model was limited to the scanning rates in the range of 2.24-3.84 m/min. In the future research, this range should be exceeded, especially, taking into account the lower values of scanning rate. Practical implications: The presented model could be used in order to control the microstructure and properties of hybrid surface layers, obtained as a consequence of the controlled gas-nitriding and LHT. Originality/value: his work is related to the new conception of laser modification of nitrided layers. Such a treatment provided the hybrid layers of new advantageous properties.

Microstructure and wear resistance of gas-nitrided steel after laser modification

Purpose: The aim of this work was to study the microstructure and wear resistance of hybrid surface layers, produced by a controlled gas nitriding and laser modification. Design/methodology/approach: Nitriding is well-known method of thermo-chemical treatment, applied in order to produce surface layers of improved hardness and wear resistance. The phase composition and growth kinetics of the diffusion layer can be controlled using a gas nitriding with changeable nitriding potential. In this study, gas nitriding was carried out on 42CrMo4 steel at 570°C (843 K) for 4 hours using changeable nitriding potential in order to limit the thickness of porous e zone. Next, the nitrided layer was laser-modified using TRUMPF TLF 2600 Turbo CO2 laser. Laser tracks were arranged as the multiple tracks with scanning rate vl=2.88 m/min and overlapping of about 86% using the two laser beam powers (P): 0.21 kW and 0.26 kW. Microstructure was observed by an optical microscope. Phase composition was studied using XRD. Hardness profiles in the produced hybrid layers was determined using a Vickers method. Wera resistance tests were performed using MBT-01 tester. Findings: Gas nitriding resulted in formation of compound zone, consisting of e nitrides close to the surface and a zone, composed of e + g' nitrides. Below the white compound zone, the diffusion zone occurred with nitric sorbite and precipitates of g' nitrides. In the microstructure after laser heat treatment (LHT) of nitrided layer, the zones were observed as follows: the re-melted zone (MZ) with e nitrides, nitric martensite and non-equilibrium FeN0.056 phase, the heat-affected zone (HAZ) with nitric martensite and precipitates of g' phase and the diffusion zone (DZ) without visible effect of laser treatment. Laser beam power influenced the depth of MZ and HAZ, so the thickness of hardened zone. The hardness of MZ was slightly decreased compared to the hardness of compound zone after gas nitriding. However, the significant increase in hardness was observed in HAZ. The formation of hybrid layers advantageously influenced the tribological properties. The laser-heat treated nitrided layers were characterized by improved wear resistance compared to the only gas-nitrided layer. Research limitations/implications: The effect of LHT on the microstructure and properties of gas-nitrided layer was limited to the two laser beam powers. In the future research, this range should be exceeded, especially, taking into account the lower values of laser beam power. It will result in laser modification without re-melting. Practical implications: The selection of suitable LHT parameters could provide the hybrid layers of modified microstructure and improved wear resistance. Originality/value: This work was related to the new concept of modification of nitrided layer by laser heat treatment.

Effects of laser heat treatment of steel following diffusion chromizing

Purpose: This paper presents the findings of a study of laser heat treatment of C45 steel following diffusion chromizing. The aim of the study was to assess the effect of laser heating of steel subjected on the microstructure of its surface layer. Design/methodology/approach: Diffusion chromizing was conducted at the temperature of 1050°C for 8 hours in a LABOTHERM LH15/14 laboratory furnace. A powder mixture of the following composition was used to produce the layer: Cr2O3 with an addition of Al, kaolin and an activator – ammonium chloride NH4Cl. Diffusion chromizing of C45 steel was followed by laser heat treatment with a dual diode TRUDISK 1000 laser device. The treatment was carried out in four variants with a laser beam of 400 to 900 W. The microstructure of the surface layer was assessed with a scanning electron microscope Tescan Vega 5135. Hardness tests were carried out by the Vickers method on crosswise microsections. The chemical composition of the diffusion layer was assessed by optical emission spectrometry. Findings: The results revealed the presence of a modified surface layer following laser heat treatment in each of the variants. Research limitations/implications: This study focuses on the effect of laser heating of C45 steel subjected to diffusion chromizing on the microstructure of its top layer. Presented research are the first step of the investigation of the surface layer of steel after diffusion chromizing and laser treatment. Next one will be consisted in detailed investigation of microstructure (phases identification) of the achieved surface layer using (among other methods) X-ray diffraction. Practical implications: Laser heat treatment of C45 steel after diffusion chromizing can be applied to parts of machines and devices used in various branches of industry exposed to tribological wear and corrosion. Originality/value: The results of the experiment were affected by the composition of the powder mixture and process parameters of the diffusion chromizing and the laser treatment.

Effect of laser solution-treatment on a Ti-based shape memory alloy

Ti-based shape memory alloys are usually heat-treated to produce consistent properties for engineering applications. The objective of this study is to investigate the effects of laser heat treatment on the mechanical properties and superelasticity of Ti72Nb15Zr10Al3 alloy. Samples heat-treated with a single-mode fiber laser (1070nm) were compared with a sample conventionally heat-treated in a furnace at 800°C for 1800s. The samples that were laser heat-treated at 50W for 10s and 100W for 1s had similar mechanical properties. The deformation-induced phase transformation behavior was measured by in situ X-ray diffraction. Recrystallization and grain coarsening during laser heating were observed by high-energy X-ray diffraction. Laser heat treatment achieved the same effects as conventional heat treatment in 1/1000 of the time. Thus, laser heat treatment may be a useful method, especially for fine and precision parts.

Effects of laser heat treatment on salt spray corrosion of 1Cr5Mo heat resistant steel welding joints

The surface of 1Cr5Mo heat-resistant steel welding joint was processed with CO2 laser, and the corrosion behaviors before and after laser heat treatment (LHT) were investigated in the salt spray corrosion environments. The microstructures, phases, residual stresses and retained austenite content of 1Cr5Mo steel welding joint before and after LHT were analyzed with optical microscope and X-ray diffraction, respectively. The cracking morphologies and chemical compositions of corrosion products after salt spray corrosion were analyzed with field emission scanning electron microscopy (FESEM) and energy disperse spectroscopy (EDS), respectively, the polarization curves were measured on a PS-268A type electrochemical workstation, and the mechanism of corrosion resistance by LHT was investigated as well. The results show that the passive film of original sample is destroyed owing to the corrosive media penetrating into the subsurface, resulting in the redox reaction. The content of residual austenite in the surface and the self-corrosion potential are increased by LHT, which is contributed to improving the capability of salt spray corrosion resistance.

Effects of laser heat treatment on the fracture morphologies of X80 pipeline steel welded joints by stress corrosion

The surfaces of X80 pipeline steel welded joints were processed with a CO2 laser, and the effects of laser heat treatment (LHT) on H2S stress corrosion in the National Association of Corrosion Engineers (NACE) solution were analyzed by a slow strain rate test. The fracture morphologies and chemical components of corrosive products before and after LHT were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively, and the mechanism of LHT on stress corrosion cracking was discussed. Results showed that the fracture for welded joints was brittle in its original state, while it was transformed to a ductile fracture after LHT. The tendencies of hydrogen-induced corrosion were reduced, and the stress corrosion sensitivity index decreased from 35.2% to 25.3%, indicating that the stress corrosion resistance of X80 pipeline steel welded joints has been improved by LHT.

Effects of laser heat treatment on mechanical properties of ceramic coated steelsPart 2 – Fracture strength of laser heat treated ceramic thin film

In our previous study, we proposed a new surface modification technique by combination of ceramic coating and laser heat treatment. By applying laser heat treatment after coating, it was possible to improve the adhesive strength and substrate hardness of ceramic coated steels without compromising the film hardness. However, the effects of laser heat treatment on the fracture strength of ceramic thin films were not investigated yet. In the present research, in order to demonstrate further development of this method, the fracture strength of laser irradiated ceramic thin films (CrAlN, TiAlN and CrN) was investigated by sphere indentation testing. To prevent heat induced changes in the substrate hardness, a cemented carbide WC–Co rather than steel was used as substrate material. While the fracture strength of each film decreased significantly through furnace heat treatment, it remained almost unchanged in case of the laser irradiated films. The application of laser heat treatment for the substrate quenching after coating process can effectively prevent the fracture strength loss of ceramic thin film.