Laser Surface Heat Treatment Research Articles

Strength-Ductility Mechanism of CoCrFeMnNi High-Entropy Alloys with Inverse Gradient-Grained Structures.

The microstructures and mechanical properties of equiatomic CoCrFeMnNi high-entropy alloys (HEAs) treated with various processing parameters of laser surface heat treatment are studied in this paper. The typical inverse gradient-grained structure, which is composed of a hard central layer and a soft surface layer, can be obtained by laser surface heat treatment. A much narrower gradient layer leads to the highest yield strength by sacrificing ductility when the surface temperature of the laser-irradiated region remains at ~850 °C, whereas the fully recrystallized microstructure, which exists from the top surface layer to the ~1.05 mm depth layer, increases the ductility but decreases the yield strength as the maximum heating temperature rises to ~1050 °C. Significantly, the superior strength-ductility combination can be acquired by controlling the surface temperature of a laser-irradiated surface at ~1000 °C with a scanning speed of ~4 mm/s due to the effect of hetero-deformation-induced strengthening and hardening, as well as the enhanced interaction between dislocation and nanotwins by the hierarchical nanotwins. Therefore, retaining the partial recrystallized microstructure with a relatively high microhardness in the central layer, promoting the generation of hierarchical nanotwins, and increasing the volume proportion of gradient layer can effectively facilitate the inverse gradient-grained CoCrFeMnNi HEAs to exhibit a desirable strength-ductility synergy.

Effects of fiber laser treatment on properties of Ti-64 alloy

Titanium (Ti) is a metal used extensively in aerospace, automotive industry and medical implants due to its exceptional combination of strength, corrosion resistance, and biocompatibility. The researchers have shown a lot of interest in exploring the areas for further enhancement of properties of Titanium alloy and to widen the range of applications. In current years, laser treatment has gained attention as an attractive method to modify the surface properties of these alloys, aiming to enhance their mechanical, chemical, and biological attributes. This study systematically examines the impact of various laser parameters, such as scan speed, and laser power, on the microstructural changes, mechanical properties, corrosion resistance, and surface wettability of titanium alloys. In the present research, laser treatment was performed on Ti alloy to study its effect on surface properties by Fiber laser heat treatment (LHT). The Ti-64 alloy (Ti-6Al-4 V) was selected LHT carried out and the surface integrity of the Ti alloy was analyzed before and after the laser process. The fiber laser of power 1600 W with a scanning speed of 7 mm/s and frequency 5000 Hz was used and nitrogen was used as shielding gas with a pressure of 10 bar. Micro Vickers hardness test, Optical Microstructure and Immersive Corrosion test have been carried out to scrutinize the impact of the laser surface heat treatment process. In the microstructure, the coarsened alpha phase in the matrix of the beta phase was transformed into an elongated alpha phase after laser treatment, increasing the grain boundary and hence the hardness. It was noticed that there was a 9 % increase in the hardness of Ti alloy after LHT in comparison with before LHT. The corrosion resistance of Ti alloy was enhanced significantly after LHT.

Wear Resistance Improvement of Alloy Steel Using Laser Surface Treatment

Laser surface heat treatment has been accepted as an effective technique of surface hardening of steels because of the converging of the laser beam by the lens on a tiny spot with a diameter near the value of the laser wavelength, laser surface heat treatment has been an effective way to improve the surface properties of. There are many applications in the industrial of the laser technique. This concentrated a lot of energy into a tiny area, resulting in a lot of heat compared to traditional heating methods. Wear resistance is a surface phenomenon, although it is influenced by elements such as surface hardening, surface condition, and microstructure. In this research, the aNd-YAG laser was used to treat the surface of alloy steel in order to investigate the effects of irradiation on the microstructure, metal surface hardening, and wear resistance. Low surface roughness and increased surface microhardness have been achieved due to the laser pulse indicated (900 Hv). The wear resistance was discovered to be higher due to laser treatment with the selected conditions.

SELECTIVE SURFACE HARDENING OF GEAR MECHANISM SHAFT BY ROBOTIC LASER 3D SYSTEM

A robot-based laser 3D hardening method is proposed as a finishing operation to increase the wear resistance of the metal end-products. The laser hardening process of the surface layer of the products by changing its structure is one of the most effective methods of selective surface hardening. Thermal hardening of metals and alloys by laser radiation is based on local heating of a surface area under the influence of radiation and subsequent cooling of this surface area at a supercritical speed due to heat removal into the inner layers of the metal. The used robot-based laser 3D system (FANUC industrial robot and SCANLAB scanning optics) allows processing the surfaces of any complexity and geometry, including the shafts of the gear mechanism of the seed drill. It was found that the development and improvement of the technological process of manufacturing steel shafts of the gearbox of the seed drill is an urgent technological problem due to the rapid retirement of the shaft, which leads to the expenditure of time and money for its replacement. The most heavily loaded sections of the shaft were pre-estimated using the SolidWorks Simulation software package. A high-power TruDisk 8002 solid-state disk laser with a maximum laser power of 8 kW and a wavelength of laser radiation of 1030 nm is used for high-quality laser surface treatment of the AISI 1066 steel shaft of the gear mechanism. The laser surface heat treatment was carried out using a constant power strategy (continuous mode), varying the laser power in the range of 1.35–2.25 kW. Based on the Fe-Mn two-component state diagram, the critical points of the temperature of complete austenization of the studied steel were previously predicted taking into account the chemical composition of the material. Additionally, the energy density values of the laser beam with a diameter of 1 mm on the working surface was estimated. The results showed that the surface hardness of the shaft was about 2.5 times higher compared to the untreated surface. The working ranges of laser heat treatment parameters of the gearbox shaft were established to increase the hardening intensity (100–150%) of the responsible areas.

Laser Surface Hardening of Graphite Cast Iron

Two types of graphite cast iron are evaluated. The effect of laser surface hardening is compared using metallographic analysis of the microstructure and measurement of hardness profile. Conditions of the hardening were the same for both analyzed materials. The alloys that were compared are: cast iron with lamellar graphite EN GJL-200 and cast iron with nodular graphite EN GJS-700 CuNi. Microstructure of tested cast irons was pearlitic-ferritic. Laser surface heat treatment caused formation of martensitic layer. The depth and structural compositions of hardened layers do differ. In the case of gray cast iron the higher hardened depth was achieved and in the case of ductile cast iron the higher hardness was observed.

Effect of laser remelting and heat treatment on microstructure and wear resistance of 2A97 Al-Li alloy

Effects of laser surface remelting and heat treatment on microstructure and wear resistance of 2A97 Al-Li alloy were studied. The results show that hardening layer with fine grain and small size eutectic phase is easily prepared by laser remelting technique with rapid solidification characteristics. The cross section of molten pool after laser remelting is mainly composed of fine equiaxed grains (about 10 μm in size) close to fusion line, elongated columnar grains and coarse equiaxed grains on top of molten pool. Divorced eutectic phase Al2Cu is formed at grain boundary, and T2 phase (Al6CuLi3) with five times symmetric axis is observed. Fine grain strengthening and solution strengthening are main reasons for higher microhardness (105 HV) of remelting sample than that of matrix (85 HV). Hardness and wear resistance of remelting alloy are improved significantly by simple heat treatment. After 520 °C/1.5 h + 175 °C/24 h, discontinuous Al2Cu eutectic phase is no longer reticular distribution, and the size is greatly reduced. δ' phase (Al3Li), T1 phase (Al2CuLi) and σ (Al5Cu6Mg2) phase are precipitated during aging. Due to precipitation of reinforcements, microhardness of laser remelted Al-Li Alloy is increased from 105 HV to 142 HV, and elastic modulus is increased from 79.734 GPa to 91.962 GPa. The wear forms of Al-Li alloy are mainly abrasive wear and adhesive wear. Simple heat treatment significantly improves wear resistance of remelted Al-Li alloy, and wear rate is only 39.62 % of matrix.

DLC coating over pre-oxidized and textured Ti6Al4V for superior adhesion and tribo-performance of hip implant

Superior surface characteristics, tribological performance and adhesion strength are critical for DLC coated surface in hip implant. Incorporating laser surface texturing and heat treatment before DLC deposition can improve surface properties by inducing oxygen diffusion and phase formation. Therefore, oriented crosshatch textures were fabricated over Ti6Al4V surface using Nd:YAG laser. Textured surface was heat treated followed by DLC coating deposition with Cr interlayer. Effect of heat treatment over DLC coating morphology, adhesion strength and surface characteristics was analyzed. Phase formation and bonding behavior at the coating interlayer were characterized and correlated with adhesion strength. Bio-tribological performance of modified surface was evaluated under elliptical sliding contact to replicate hip implant articulation. Increased surface roughness, better wettability and enhanced graphitic characteristics were associated with DLC coating with prior heat treatment. With heat treatment, Cr2O3 and TiO2 phase formation with superior bonding at interlayer demonstrated improved adhesion strength including deformation resistance. Textured, heat treated and DLC coated surface showed relatively increased compressive residual stress with HF1 quality adhesion. The synergic effect of surface texturing and DLC coating achieved lowest friction. Qualitative wear analysis using Raman spectroscopy reveals beneficial effect of heat treatment before DLC coating for long term hip implant application.

10 kW rectangular laser beam generation with incoherent space combiner

In this paper, we report an incoherent space laser beam combiner for rectangular beam combination with 18 fiber-transmitted semiconductor lasers at 972 nm wavelength. The coupled thermo-mechanical properties of all the optical lenses in the combiner were analyzed to evaluate the long-term reliability of the combiner subjected to beyond 10 kW high-power laser irradiation. An experiment-based numerical model was developed on the basis of the multi-beam laser volumetric heat source, and the performance of lenses irradiated by 10 kW combined laser for 1000 s was studied with finite element method (FEM). The maximum temperature among all lenses was 427.27 K which is much lower than the softening point temperature of fused silica material made of lenses. And the 0.1 aperture number corresponding to the maximum thermal deformation of 4.53 µm is much smaller than the conventional optical lens processing tolerance. The maximal stress of 12.73 MPa is far less than the yield stress of 4.5 GPa for the material. The manufactured laser beam combiner realized a highest output power of 10.641 kW at a power combination efficiency of 98.5%, a combination length of 200 mm and a rectangular focal beam spot of 30 mm × 10 mm. Our method provides a valuable choice for realizing fast and flexible laser surface heat treatment.

Tribological Performance of Crosshatch Pattern Textured and Heat Treated Dual Engineered Ti6Al4V Surface under Bio-Lubricated Line Contact Configuration

This study combines the laser surface texturing technology and heat treatment process to fabricate a dual surface engineered Ti6Al4V consisting of micro-groove crosshatch pattern texture covered with hard TiO2 oxide coating to reduced friction and improve the wear resistance at the bio-lubricated interface. Crosshatch texture with 25 μm width, 5 μm depth at 25% area density were fabricated using nanosecond Nd:YAG laser over Ti6Al4V surface and then heat treated at 600 °C for 48 hours. XRD result showed rutile TiO2 phase formation along with the presence of anatase TiO2, Al2O3 and Ti3O minor phases whereas, the surface hardness was increased to 1538±41 HV. Bio-tribology experiments were carried out for 45 and 90 o oriented micro-groove crosshatch textures, with and without heat treatment, under partially replicating hip implant articulation. Results demonstrated 60% friction reduction corresponding to the 45 o oriented crosshatch texture with heat treatment. Further, the worn-out surface morphology showed reduced wear damage and good wear debris entrapment inside the micro-grooves.

Improved oxygen diffusion and overall surface characteristics using combined laser surface texturing and heat treatment process of Ti6Al4V

The combination of laser surface texturing and heat treatment process was barely investigated in the past, particularly for improved surface characteristics of Ti6Al4V. Hereby, the important role of laser scanning and post heat treatment in improving the oxygen diffusion depth and overall surface characteristics was analyzed. Polished Ti6Al4V surface was scanned using Nd:YAG nanosecond laser and analyzed for the oxygen pickup, phase change and hardness variation. The laser textured surface was heat treated to grow oxide coating over textured surface. In comparison with heat treated surface, the synergic effect of laser scanning and heat treatment improved the surface hardness by 15% and raised the TiO 2 rutile phase fraction from 0.36 to 0.73. The dual engineered Ti6Al4V surface was found to have superior HF1 quality adhesion strength along with the presence of low magnitude tensile residual stress. The increase in oxygen diffusion depth, diffusion coefficient and TiO 2 rutile phase fraction due to synergic effect of laser scanning and heat treatment were associated to the Ti 2 O 3 and C doping assisted anatase to rutile transformation mechanism. • Laser scanning is responsible for oxygen and carbon pickup and forms Ti2O3 phase at the Ti6Al4V surface. • Combination of LST and heat treatment improves rutile phase fraction, surface hardness and adhesion. • Oxygen diffusion depth and diffusion coefficient increase using laser texturing with heat treatment process. • Anatase to rutile transformation is prominent mechanism in laser textured with heat treated Ti6Al4V surface.

Effect of Laser Surface Heat Treatment on Wear and Hardness Resistance of Metal Matrix Composite from (Al- 6061+ SiC Particles)

In this paper, the effect of laser surface heat treatment on wear resistance and hardness of an aluminum alloy Al-6061 as a base material with different ratios of SiC particles as an additive was studied. The composite material was prepared from Al-6061 aluminum alloy and particles with a granular size of (10-70) μm with different weight ratios (15%, 12%, 9%, 6%, 3%), where the stirred plumbing technique was used to ensure An increase in the wettability of SiC particles in the base alloy fuse and the possibility of distributing it uniformly. The laser surface heat treatment of the composite material prepared using the Neodymium - YAG laser was performed with a power of 1J, a wavelength of 1.06 μm, a pulse time of 5 m sec, and a distance of 30 cm between the exit area of the laser from the system and the piece to be thermally treated. The results showed an improvement in the mechanical properties of the prepared composite material (hardness, wear resistance) after performing the surface heat treatment by laser. The increase in the hardness amount was 12.9% when adding 15% of particles to the base alloy. The results showed that the wear rate value decreases with increasing the added percentages of SiC particles. The results also showed that the surface heat treatment of the laser led to an improvement in the wear resistance of the prepared composite material and for all the added ratios of SiC particles at different loading pressures used and in close proportions. Also, the prepared samples were photographed using a regular optical microscope before and after the laser surface heat treatment.

Manufactural Investigations on Dissimilar Laser Cladding and Post-Clad Heat Treatment Processes of Heat-Resistant Ni Alloy on Cu Substrate

Hardness of dissimilar laser clad samples of NiCrBSi alloy on a Cu substrate was investigated, with the aim of optimizing the manufacturing process for high-durability continuous casting molds for steelmaking. The performance of the clads is compared with that of samples prepared by thermal spray coating, and an optimal process is proposed. Dissimilar laser cladding between NiCrBSi alloy and Cu was achieved with a hardness of ~450 HV using a high-power diode laser, and no cracks and pores were observed. Post-clad heat treatment performed below the melting point of the Cu substrate (1357 K) using a furnace (1223 K for 500 min) resulted in a decrease in the hardness to 142 HV, which was attributed to the dilution of the alloy with the soft Cu substrate and changes to the microstructure; the solidification microstructure was almost homogenized during the heat treatment, and secondary boride phases were formed and almost dissolved in the matrix phase. Laser surface heat treatment of the clad metal at 1323 K resulted in a decrease in the hardness (to 359 HV near the surface), with a heat treatment depth of ~1.3 mm. In contrast, the hardness of the as-sprayed coatings was 730–750 HV, which drastically increased to ~1200 HV after laser fusing because of the formation of finely distributed secondary phases. Therefore, to achieve high-durability continuous casting mold components, minimization of Cu dilution is preferentially recommended for the laser cladding of NiCrBSi alloy on Cu substrate. Furthermore, when it is difficult to minimize the Cu dilution during the laser cladding, thermal spraying in conjunction with laser fusing treatment appears to be sufficiently applicable for high-durability continuous casting molds.

Temperature evolution, phase ratio and corrosion resistance of duplex stainless steels treated by laser surface heat treatment

• Laser surface heat treatment (LSHT) was performed on duplex stainless steels 2304, 2205, and 2507. • The effect of laser spot size and cooling time t 12/8 was investigated by numerical simulation and microstructure analysis. • LSHT obtained the peak temperature, the t 12/8 and the effective depth as 1350 °C, 8.9 s and 1.5 mm respectively. • Austenite percentage increased from 2%, 5%, and 38% to 27%, 36% and 55 % respectively for 2304, 2205, and 2507. • LSHT increased the corrosion pitting temperature from 13, 42 and 66 °C to 19, 52 and 76 °C respectively for 2304, 2205, and 2507. Duplex stainless steels (DSS) are promising materials due to excellent corrosion resistance and good mechanical properties. However, the corrosion resistance of DSS welded joints deteriorates unavoidably due to the unbalanced phase ratio, namely a low austenite percentage resulted from the welding thermal cycle. Laser surface heat treatment (LSHT) exhibits tremendous advantages to restore the corrosion resistance especially regarding efficiency and flexibility. By adjusting laser energy input, including laser power and spot size, different LSHT conditions were applied to DSS 2304, 2205 and 2507, whose austenite content were deliberately decreased to a very low percentage. The temperature evolution during the LSHT was calculated out by finite element analysis. Critical pitting temperature (CPT) was measured to evaluate the corrosion resistance. A long length of laser spot and a slow scanning speed were beneficial for increasing the austenite percentage during the LSHT. With the length of laser spot as 100 mm and the scan speed as 2 mm/s, the laser power was adjusted to obtain a target peak temperature of 1350 ℃, which provided a cooling time t 12/8 as 8.9 s and an effective action depth as 1.5 mm. For DSS 2304 and 2205, the austenite percentage increased from 2% and 5% in deteriorated samples to 28 % and 56 % after the LSHT; the CPT increased from 12.5 and 42.3 ℃ to 19.2 and 51.8 ℃ respectively. DSS 2507 remained the highest austenite percentage after the same deterioration and exhibited the best corrosion resistance under all the used conditions. The influence of LSHT processing parameters and material compositions on the phase transformation and the corrosion resistance was discussed accordingly.

Present Status and Future Directions of High Performance Cutting in Aerospace Manufacturing

Manufacturing remains the largest and most important wealth generating sector. Within this sector, material cutting is a key technology in the aerospace and automotive industries, contributing to more than C$200 billion to the economy in North America on annual basis. The demand for high productivity and high accuracy is steadily increasing, along with the increasing attention to the impact on the environment. With more than 700 companies in the aerospace sector, Canada has been ranked third globally in terms of global civil aircraft production, especially for aerostructures, providing more than C$27 billion of direct revenue annually. It is clear that improvement and optimization of metal cutting processes are essential for continuous improvement in this sector. This paper presents the recent advances in high-performance cutting technologies that are aligned with the I4.0 paradigm through featuring environmental and economical sustainability, effective digital inter-connectivity and integrated intelligence. The focus in this paper is placed on the following enabling technologies: (i) Superabrasive grinding using diamond and Cubic Boron Nitride (CBN) abrasives for grinding difficult-to-cut aerospace materials. (ii) Integrated process of laser-assisted machining (LAM) and laser surface heat treatment. (iii) New sustainable hybrid cooling using liquid nitrogen (LN2) with minimum quantity lubrication (MQL). (iv) Intelligent tool condition monitoring (TCM) to predict and prevent tool failure. (v) Virtual machining for tool geometry and cutting conditions optimization in drilling of fiber reinforced polymers (FRPs) and hybrid stacks.

Laser surface treatment of α-β titanium alloy to develop a β -rich phase with very high hardness

• Laser surface treatment results microstructural gradient in laser affected zone (LAZ). • Plasma plume detachment at higher power result in surface roughness enhancement. • Beta enrichment in LAZ with higher hardness. • Rosette structure formation. The α - β titanium alloy VT31 is used in the aerospace industry due to its high strength to weight ratio and good mechanical properties at elevated temperatures. Surface microstructure plays an important role in the mechanical behavior of the material, especially fatigue. In this work, VT3-1 α - β titanium alloy surface microstructure was modified using laser surface heat treatment. Laser surface treatment (LST) was carried out at various laser powers (100−250 W) and scanning speeds (150−500 mm/min). Laser affected zones, surfaces and sub-surfaces were characterized using different techniques. Electron backscatter diffraction (EBSD) analysis of the laser affected zone exhibits a distinct microstructure across the depth of the specimen, and it changes with laser power and scanning speed. At a lower scanning speed and high laser power (200−250 W); almost complete β -containing microstructure was developed at the surface with very high hardness. At an intermediate power (150−200 W), a β -rich surface layer with dendritic features followed by a layer of martensitic microstructure was evident. Interestingly, at high power (250 W) a distinct shiny surface with a lower surface roughness was observed. Moreover, the microstructure under this condition corresponds to an α -phase (transformed microstructure) which is typical of melted and fast cooled α - β titanium alloy. Finite element analysis of the LST was also carried out to predict thermal history based on which the extent of the laser affected zone across the depth was predicted for various processing parameters and correlated with the hardness variation.

Surface hardening characteristics of press die cast iron and plastic mold steel according to laser heat input

In this study, the surface heat treatment of mold materials was performed using a high-power laser heat source and surface hardening characteristics were investigated. Laser surface heat treatment is a hardening method in which a surface is heated using high-density energy and self-quenched through rapid cooling. Hence, the heat input during laser heat treatment is important. The heat input for the surface hardening of each material was compared, and it was found that the heat input for each mold material was different. Additionally, die cast iron has higher thermal conductivity compared to mold steel, resulting in a larger heat input during heat treatment.

Study on the Selective Surface Modification of Injection Mold Steels by Laser Materials Processing: Relationship Between AlN Formation and Surface Hardening During Laser Nitriding

Laser surface heat treatment and laser nitriding processes were applied using selective surface modification techniques to investigate phase transformation, microstructural evolution, and surface hardening behaviors for two types of plastic injection mold steels, AISI 1045 and P21. During laser surface heat treatment, a 245% hardness increase compared to that of the base metal (290 HV) was achieved due to martensite transformation of the AISI 1045 steel. However, for the AISI P21 steel, hardness within the heat-treated zone was largely unchanged from that of the base metal (410 HV) despite being accompanied by martensite transformation. Compared to that of the base metal, this static hardness behavior of the heat treated P21 steel was due to coarsening of Cu particles induced by the laser irradiation. To overcome the static hardness behavior of P21 steel, laser nitriding was used. The laser-nitrided specimen (at 4500 J/mm heat input) was approximately 40% (577 HV) harder than the base metal (410 HV) and was highly correlated with nitride formation. Nitrogen successfully penetrated the surface of the specimen during laser irradiation and formed a nitrided layer mainly composed of an AlN phase. Thus, the surface hardening behavior of AISI P21 steel after laser nitriding could be largely attributed to the AlN phase development. Key words: plastic injection mold steels, surface modification, laser surface heat treatment, laser nitriding, nitride

Experimental Study on Effect of Laser Hardening Parameters on Carbon Steel, Non-Malleable Cast iron and X20Cr13 Materials

Laser hardening is a surface heat treatment process used to enhance tribological and mechanical properties of metals which also leads to increase in service life of the components. Material removal, wear and tear, load concentration occurs mostly at rotating and reciprocating parts. Hence it is sufficient to enhance the hardness of a component at functional areas rather than the entire component. Laser hardening process is designed to change the microstructure of metals through controlled heating and cooling to get a modified surface. The constraints of traditional surface heat treatment process such as inability to treat specific area, distortion, poor degree of controllability, requirement of a quenching medium, long cycle time can be overcome by using Laser surface heat treatment and in addition to that it can be automated. With its benefits Laser surface hardening turns out to be a cost effective and energy saving process. The presented work is an investigation of the laser surface hardening via experimental results making use of a 6 axis robotic arm and a 10KW high power diode laser system as heat source with a wavelength of 980nm on leading automotive parts such as retainer, hub, and turbine blade whose materials being non-malleable cast iron, carbon steel, X20Cr13 respectively. Process parameters such as laser power from power source, scan speed were varied to understand the influence on resulting heat treated surface and efforts were made to optimize the process parameters to attain maximum hardness for the component to enhance its working life.

Surface Treatment of AISI M2 Tool Steel by Laser Melting

Attempt was made to improve the surface hardness and wear properties of AISI M2 high speed tool steel. Laser surface melting (LSM) of tool steel was conducted with 2.2 KW Nd:YAG laser as heating source. Conventional hardening of the tool steel was applied. Characterizing the LSM, with optical and field emission scanning electron microscopy and surface hardness technique was used to evaluate the micro-hardness and mechanical behaviour of different regions of melting pool. AISI M2 tool steel is approximately HV 260, hardness after conventional treatment was 850 HV and the hardness after laser surface heat treatment is around 900 HV. It was found that there is a considerable influence of the laser power density and scanning velocity on the melted zone dimensions and the re-solidified structure. Increasing laser energy and reducing the laser scanning rate results in deeper and wider melt pool formation.

Temperature Modeling of AISI 1045 Steel during Surface Hardening Processes.

A Coupled thermo-mechanical finite element model was employed to simulate the possible effects of varying laser scanning parameters on the surface hardening process for AISI 1045 and AISI 4140 steels. We took advantage of the high-power density of laser beams to heat the surface of workpieces quickly to achieve self-quenching effects. The finite element model, along with the temperature-dependent material properties, was applied to characterize the possible quenching and tempering effects during single-track laser surface heat treatment. We verified the accuracy of the proposed model through experiments. The effects of laser surface hardening parameters, such as power variation, scanning speed, and laser spot size, on the surface temperature distribution, hardening width, and hardening depth variations during the single-track surface laser treatment process, were investigated using the proposed model. The analysis results show that laser power and scanning speed are the key parameters that affect the hardening of the material. The numerical results reveal that the proposed finite element model is able to simulate the laser surface heat treatment process and tempering effect of steel.