Reduced Laser Power Research Articles

Effect of laser power during laser powder bed fusion on microstructure of joining interface between Tungsten and AISI 316L steel

This study investigates the deposition of tungsten (W) onto a 316L steel substrate by laser powder bed fusion (L-PBF), to optimize process parameters and analyze the interface between W and 316L. To obtain high-density W structure (98.89%), the optimal laser power was 350 W, and scan speed was 500 mm/s, but these parameters cause significant dilution of W in the W-316L interface; as a result, Fe7W6 intermetallics form, despite L-PBF being a non-equilibrium solidification process. These intermetallics which are brittle could degrade joint strength. By reducing laser power below 250 W, the dilution of W can be mitigated, and potentially minimize formation of intermetallics and increase joint stability for advanced manufacturing applications.

Self-enhanced regulation of stable organic radicals with polypeptide nanoparticles for mild second near-infrared phototheranostics

Stable organic radicals have emerged as a promising option to enhance fluorescence quantum yield (QY), gaining traction in medical treatment due to their unique electronic transitions from the ground state (D0) to the doublet excited state (D1). We synthesized a stable dicyanomethyl radical with a NIR-II fluorescence QY of 0.86 %, surpassing many NIR-II organic dyes. Subsequently, amphiphilic polymer-encapsulated nanoparticles (NPs) containing the radical were created, achieving a NIR-II fluorescence QY of 0.32 %, facilitating high-contrast bio-imaging. These CNPPs exhibit self-enhanced photothermal properties, elevating photothermal conversion efficiency (PCE) from 43.5 % to 57.5 % under 915 nm laser irradiation. This advancement enables more efficient photothermal therapy (PTT) with lower dye concentrations and reduced laser power, enhancing both feasibility and safety. Through regular fractionated mild photothermal therapy, we observed the release of damage-associated molecular patterns (DAMPs) and an increase in cytokine expression, culminating in combined mild phototherapy (m-PTT)-mediated immunogenic cell death (ICD). Consequently, we developed an immunostimulatory tumor vaccine, showcasing a novel approach for refining photothermal agents (PTA) and optimizing the PTT process.

Optimising the manufacturing of a β-Ti alloy produced via direct energy deposition using small dataset machine learning

Successful additive manufacturing involves the optimisation of numerous process parameters that significantly influence product quality and manufacturing success. One commonly used criteria based on a collection of parameters is the global energy distribution (GED). This parameter encapsulates the energy input onto the surface of a build, and is a function of the laser power, laser scanning speed and laser spot size. This study uses machine learning to develop a model for predicting manufacturing layer height and grain size based on GED constituent process parameters. For both layer height and grain size, an artificial neural network (ANN) reduced error over the data set compared with multi linear regression. Layer height predictions using ANN achieved an R2 of 0.97 and a root mean square error (RMSE) of 0.03 mm, while grain size predictions resulted in an R2 of 0.85 and an RMSE of 9.68 μm. Grain refinement was observed when reducing laser power and increasing laser scanning speed. This observation was successfully replicated in another α + β Ti alloy. The findings and developed models show why reproducibility is difficult when solely considering GED, as each of the constituent parameters influence these individual responses to varying magnitudes.

New Scheme of MEMS-Based LiDAR by Synchronized Dual-Laser Beams for Detection Range Enhancement.

A new scheme presents MEMS-based LiDAR with synchronized dual-laser beams for detection range enhancement and precise point-cloud data without using higher laser power. The novel MEMS-based LiDAR module uses the principal laser light to build point-cloud data. In addition, an auxiliary laser light amplifies the single-noise ratio to enhance the detection range. This LiDAR module exhibits the field of view (FOV), angular resolution, and maximum detection distance of 45° (H) × 25° (V), 0.11° (H) × 0.11° (V), and 124 m, respectively. The maximum detection distance is enhanced by 16% from 107 m to 124 m with a laser power of 1 W and an additional auxiliary laser power of 0.355 W. Furthermore, the simulation results show that the maximum detection distance can be up to 300 m with laser power of 8 W and only 6 W if the auxiliary laser light of 2.84 W is used, which is 35.5% of the laser power. This result indicates that the synchronized dual-laser beams can achieve long detection distance and reduce laser power 30%, hence saving on the overall laser system costs. Therefore, the proposed LiDAR module can be applied for a long detection range in autonomous vehicles without requiring higher laser power if it utilizes an auxiliary laser light.

Melt pool monitoring and process optimisation of directed energy deposition via coaxial thermal imaging

In Laser-based Directed Energy Deposition of metal powder, the use of optimised parameters allows the deposition of defect-free material, while diverging from these optimised parameters can typically result in high porosity, high dilution or different track geometry. One of the main challenges when building complex geometries is that the geometrical and thermal conditions of the deposition are constantly changing, which requires to adjust the process parameters during the production. In order to facilitate this process, sensors such as thermal cameras can be used to extract data from the process and adapt the parameters to keep the process stable despite external disturbances. In this research, different signals extracted from a coaxial thermal camera are investigated and compared for process optimisation. To investigate such possibilities, five overlapped tracks are deposited at constant laser powers in order to extract average pixel values as well as the melt pool area, length, width and orientation. The behaviour of each track deposition is modelled as a function of the laser power, and these models are used to calculate and test laser power reduction strategies based on different signals. The results show that the melt pool area is the most relevant signal to use for an efficient process control, resulting in a stable process with only ±1.6 % of signal variation from track to track.

Fabricating process-electrochemical property correlation of laser-scribed graphene and smartphone-based electrochemical platform for portable and sensitive biosensing

Laser-scribed graphene (LSG), a promising electrode material has attracted special research interest in recent years. Here, the fabricating process-electrochemical property correlation of laser-scribed graphene (LSG) devices was discussed emphatically and a pertinent optimization was performed to achieve better electroanalytical performance. Experiment results indicated that the laser scribing technique possessed great process latitude and reducing laser power and scribing speed facilitated fabricating high-quality graphene electrodes. Benefiting from its binder-free 3D porous network structure and high active/geometric area ratio, the optimized LSG electrode was superior to the screen-printed carbon electrode (SPCE) on electrochemical performance in the [Fe(CN)6]3-/4- redox system. Integrating the LSG electrode with a homemade hand-held detector, a portable electrochemical sensing platform with smartphone readout was developed. It realized a specific detection of H2O2 (linear range: 0.02–3.4 mM, sensitivity: 24.56 μA mM−1 cm−2), glucose (linear range: 0.04–4.0 mM, sensitivity: 16.35 μA mM−1 cm−2) by directly decorating biological enzymes without artificial redox mediator and featured a satisfactory comprehensive performance. The constructed immunosensor for tumor necrosis factor-α exhibited a wide linear range (2–500 pg mL−1) and a 4.3-fold enhancement in sensitivity compared with that of SPCE. With satisfactory selectivity, reproducibility, and sensitivity, the developed smartphone-based electrochemical sensing platform held great promise in accurate detection on the spot. This work also provided a significant reference for tailoring binder-free carbonaceous electrode materials toward the desired application.

Improved imaging and preservation of lysosome dynamics using silver nanoparticle-enhanced fluorescence.

The dynamics of living cells can be studied by live-cell fluorescence microscopy. However, this requires the use of excessive light energy to obtain good signal-to-noise ratio, which can then photobleach fluorochromes, and more worrisomely, lead to phototoxicity. Upon light excitation, noble metal nanoparticles such as silver nanoparticles (AgNPs) generate plasmons, which can then amplify excitation in direct proximity of the nanoparticle's surface and couple to the oscillating dipole of nearby radiating fluorophores, modifying their rate of emission and thus, enhancing their fluorescence. Here, we show that AgNPs fed to cells to accumulate within lysosomes enhanced the fluorescence of lysosome-targeted Alexa488-conjugated dextran, BODIPY-cholesterol, and DQ-BSA. Moreover, AgNP increased the fluorescence of GFP fused to the cytosolic tail of LAMP1, showing that metal enhanced fluorescence can occur across the lysosomal membrane. The inclusion of AgNPs in lysosomes did not disturb lysosomal properties such as lysosomal pH, degradative capacity, autophagy and autophagic flux, and membrane integrity, though AgNP seemed to increase basal lysosome tubulation. Importantly, by using AgNP, we could track lysosome motility with reduced laser power without damaging and altering lysosome dynamics. Overall, AgNP-enhanced fluorescence may be a useful tool to study the dynamics of the endo-lysosomal pathway while minimizing phototoxicity.

Super-Low-Dose Functional and Molecular Photoacoustic Microscopy.

Photoacoustic microscopy can image many biological molecules and nano-agents in vivo via low-scattering ultrasonic sensing. Insufficient sensitivity is a long-standing obstacle for imaging low-absorbing chromophores with less photobleaching or toxicity, reduced perturbation to delicate organs, and more choices of low-power lasers. Here, the photoacoustic probe design is collaboratively optimized and a spectral-spatial filter is implemented. A multi-spectral super-low-dose photoacoustic microscopy (SLD-PAM) is presented that improves the sensitivity by ≈33 times. SLD-PAM can visualize microvessels and quantify oxygen saturation in vivo with ≈1% of the maximum permissible exposure, dramatically reducing potential phototoxicity or perturbation to normal tissue function, especially in imaging of delicate tissues, such as the eye and the brain. Capitalizing on the high sensitivity, direct imaging of deoxyhemoglobin concentration is achieved without spectral unmixing, avoiding wavelength-dependent errors and computational noises. With reduced laser power, SLD-PAM can reduce photobleaching by ≈85%. It isalso demonstrated that SLD-PAM achieves similar molecular imaging quality using 80% fewer contrast agents. Therefore, SLD-PAM enables the use of a broader range of low-absorbing nano-agents, small molecules, and genetically encoded biomarkers, as well as more types of low-power light sources in wide spectra. It isbelieved that SLD-PAM offers a powerful tool for anatomical, functional, and molecular imaging.

Annular laser metal deposition of Ti-6Al-4V alloy in a semi-open environment: Process optimization, microstructure and mechanical properties

Laser metal deposition (LMD) in open environment is beneficial for the forming of large parts or the online repairing of damaged components. A major challenge in successful deposition of active materials is oxidation. The surface chromatic aberration is adopted to represent the oxidized discoloration. In this paper, response surface methodology (RSM) is used to obtain the process parameters of a single layer of Ti-6Al-4V alloy with low surface chromatic aberration in a semi-open environment, based on annular laser metal deposition (ALMD) process. The results show that low surface chromatic aberration is achieved by appropriately reducing laser power, and increasing powder feeding rate and shielding flow rate. There is good agreement between the predicted and experimental values. The desirability approach is employed for determining the optimal processing window to obtain the deposited layer less than surface chromatic aberration threshold of 5.09 based on oxygen concentration analysis. Furthermore, the microstructure and mechanical properties are investigated. The yield strength of 907 MPa and elongation of 6.5% are achieved at the optimum parameter settings. This study establishes a methodology towards successful deposition of Ti-6Al-4V alloy in a semi-open environment.

Shock-Augmented Ignition Approach to Laser Inertial Fusion

Shock ignition enables high gain at low implosion velocity, reducing ablative Rayleigh-Taylor instability growth, which can degrade conventional direct drive. With this method, driving a strong shock requires high laser power and intensity, resulting in inefficiencies in the drive and the generation of hot electrons that can preheat the fuel. A new "shock-augmented ignition" pulse shape is described that, by preconditioning the ablation plasma before launching a strong shock, enables the shock ignition of thermonuclear fuel, but importantly, with substantially reduced laser power and intensity requirements. The reduced intensity requirement with respect to shock ignition limits laser-plasma instabilities, such as stimulated Raman and Brillouin scatter, reducing the risk of hot-electron preheat and restoring the laser coupling advantages of conventional direct drive. Simulations indicate that, due to the reduced power requirements, high gain (∼100) ignition of large-scale direct drive implosions (outer radius ∼1750 μm, deuterium-tritium ice thickness ∼165 μm) may be possible within the power and energy limits of existing facilities such as the National Ignition Facility. Moreover, this concept extends to indirect drive implosions, which exhibit substantial yield increases at reduced implosion velocity. Shock-augmented ignition expands the viable design space of laser inertial fusion.

Synthesis and characterization g‐C3N4‐doped PMMA polymeric nanocomposites films for electronic and optoelectronic applications

AbstractSolution casting was used to synthesis polymethyl methacrylate (PMMA) nanocomposites with graphitic carbon nitride (g‐C3N4) nanoparticles in various percentages (0.033, 0.166, 0.33, 1.665, and 3.3 wt%). XRD patterns confirmed the amorphous nature of PMMA/C3N4 nanocomposites. Optical constants are obtained at room temperature in the 200–2500 nm wavelength range. The optical band gaps of PMMA/C3N4 doped films, both direct and indirect, are measured and have values change from 4.8 to 2.32 eV for and changes from 5 to 3.7 eV for . The refractive index values of the materials were also calculated using Moss, Reddy, Anani, and Kumar‐Singh relationships with average values vary from (2.109 to 2.529) and vary from 2.155 to 2.32 for indirect and direct transition, respectively. The dielectric constant, dielectric loss, and AC electrical conductivity at RT and the g‐C3N4 doping level was examined as frequency variables from 100 to 1 MHz. In consideration of Jonscher's universal power law, the variation of σAC with frequency was examined. The addition of C3N4 appears to raise the σAC of the studied films, making them attractive for semiconductor applications. According to the optical limiting results, the samples doped with g‐C3N4 are severely attenuated for the laser beam of 638.2 nm. PMMA doped with g‐C3N4 is a viable contender for electronic and optoelectronic applications, particularly laser power reduction.

Determination of the polymer composition of mid-twentieth century purses by Raman spectroscopy

A database was constructed of 134 reference plastic samples and their Raman spectra to aid in the rapid and accurate identification of the polymer composition of mid-twentieth century plastic purses and their component parts from the Plastics Artifacts Collection at Syracuse University Libraries. Work began by making and testing the database, which led to the determination that matching artifact spectra to reference sample spectra worked well for artifact spectra having signal-to-noise ratios down to 30:1. This finding allowed for using reduced laser power as necessary to protect delicate and pigmented artifacts. These studies enabled the definitive chemical identification of seven selected artifacts, showing that the majority are composed of single plastics including polystyrene, poly(methyl methacrylate), or cellulose acetate. However, it was discovered that one of the purses was composed of both poly(methyl methacrylate) and cellulose acetate. The compositions of three artifacts of unknown composition were discovered, corrections to the existing records were made for three other artifacts, and the composition of one artifact was confirmed. This decisive study will contribute to the archival processing and preservation of these artifacts.

Effects of scanning pattern and laser power reduction in stainless Steel 316L additive manufactured by direct laser metal deposition

The major purpose of this study is to investigate two strategies for additive manufacturing processes of SS316L using the direct laser metal deposition method (DLMD). In additive manufacturing (AM), the influence of scanning patterns was the first strategy, and the other strategy was the effects of laser power reduction in various layers. The experiments used a semiconductor diode laser with a coaxial nozzle head. The goal of this study was to determine how these two techniques influenced the properties of additive-produced components. Geometrical metrics such as width, height, and penetration, as well as particle size, and microhardness profiles, were assessed in the macrosection of the fabricated wall samples. The sample’s height stability was also investigated. The results revealed that the scanning pattern significantly affects all aspects of additive-manufactured components. The results indicated that higher stability is achieved when using a unidirectional scanning sequence. The average particle size of specimens obtained using the unidirectional and bidirectional scanning patterns was 8.6 and 9.69 μm, respectively. The pattern of particle size variation in the samples demonstrates that the LMD walls in the beginning and end are larger than in the samples at the center, the microhardness fluctuation pattern is in the opposite direction of particle size. The width of the samples was also found to decrease as the laser power was reduced from the substrate upward.

Understanding Stellite-6 coating prepared by laser cladding: Convection and columnar-to-equiaxed transition

In the Stellite-6 coating prepared by laser cladding technology, temperature gradient and solidification rate play a critical role in grain growth. The columnar-to-equiaxed transformation behavior significantly affects the properties of the coating. In this paper, a finite element model including the changes of convection and temperature field in the melt pool was established, and the effects of laser power on the geometric characteristics and columnar-to-equiaxed transformation behavior of the coating were analyzed. The results show that the laser power significantly improve the convection intensity of metal liquid, which increased the width, depth and dilution ratio of the coating. In the solidification process of melt pool, convection gradually changed from diffusion around the coating to reflux to the top of the coating. Lower temperature gradient and higher solidification rate were conducive to the growth of equiaxed crystals. The microhardness of equiaxed crystal region was higher than that of columnar crystal region. Reducing laser power could accelerate the CET behavior of melt pool and improve the mechanical properties of coating.

Modeling and prediction of surface roughness and dimensional accuracy in SLS 3D printing of PVA/CB composite using the central composite design

Surface roughness and dimensional accuracy can be controlled by selecting the appropriate values for 3D printing variables. This paper investigates the effects of selective laser sintering (SLS) 3D printing main process variables and their interactions on surface roughness and dimensional accuracy. It also presents how to develop mathematical models to predict surface roughness and dimensional accuracy using a central composite design. It shows how to determine the appropriate values for the process variables to reach the desired surface roughness and dimensional accuracy separately and simultaneously. The analysis of variance is utilized to verify the adequacy of the developed models. Further, there is still a need for developing materials and composites for use with SLS technology. The combination of polyvinyl alcohol (PVA) and carbon black (CB) powder was used to print the PVA/CB composite specimens. In order to do this study, a desktop SLS 3D printer has been built. It is found that laser power, scan spacing, laser speed, and layer thickness significantly affect the surface roughness and dimensional accuracy. Also, the effects of interactions between process variables are considerable and should be determined in the surface roughness and dimensional accuracy models. The nonlinear behavior of some variables and their interactions on surface roughness are explained using the energy density plots. According to the results in the studied domains, reducing layer thickness, laser speed, and scan spacing tend to decrease the surface roughness. However, laser power reduction increases the surface roughness.

Distance-aware Approximate Nanophotonic Interconnect

The energy consumption of manycore architectures is dominated by data movement, which calls for energy-efficient and high-bandwidth interconnects. To overcome the bandwidth limitation of electrical interconnects, integrated optics appear as a promising technology. However, it suffers from high power overhead related to low laser efficiency, which calls for the use of techniques and methods to improve its energy costs. Besides, approximate computing is emerging as an efficient method to reduce energy consumption and improve execution speed of embedded computing systems. It relies on allowing accuracy reduction on data at the cost of tolerable application output error. In this context, the work presented in this article exploits both features by defining approximate communications for error-tolerant applications. We propose a method to design realistic and scalable nanophotonic interconnect supporting approximate data transmission and power adaption according to the communication distance to improve the energy efficiency. For this purpose, the data can be sent by mixing low optical power signal and truncation for the Least Significant Bits (LSB) of the floating-point numbers, while the overall power is adapted according to the communication distance. We define two ranges of communications, short and long, which require only four power levels. This reduces area and power overhead to control the laser output power. A transmission model allows estimating the laser power according to the targeted BER and the number of truncated bits, while the optical network interface allows configuring, at runtime, the number of approximated and truncated bits and the laser output powers. We explore the energy efficiency provided by each communication scheme, and we investigate the error resilience of the benchmarks over several approximation and truncation schemes. The simulation results of ApproxBench applications show that, compared to an interconnect involving only robust communications, approximations in the optical transmission led to up to 53% laser power reduction with a limited degradation at the application level with less than 9% of output error. Finally, we show that our solution is scalable and leads to 10% reduction in the total energy consumption, 35× reduction in the laser driver size, and 10× reduction in the laser controller compared to state-of-the-art solution.

Comparative study of filament-fed and blown powder-based laser additive manufacturing for transparent magnesium aluminate spinel ceramics

Magnesium aluminate spinel is of great interest as a transparent ceramic for its excellent mechanical properties and excellent optical transmittance. Additive manufacturing of this desirable material presents several benefits over traditional manufacturing methods, including reduced fabrication time and cost and the potential to fabricate structures with complex geometries and internal cooling networks. Despite the many benefits, the challenges hindering this technology must be overcome. A primary challenge with powder-based laser additive manufacturing of transparent ceramics is a trade-off between densification and cracking. The fabrication of transparent ceramics requires nearly full densification since pores act as light scattering centers. Even relatively small percentages of porosity render ceramics translucent or opaque. Previous studies on powder-based laser direct deposition of spinel ceramics have shown that densification to transparency is possible with high-laser power deposition. While high-laser powers are beneficial for densification, it also produces high thermal gradients that result in significant crack formation. Cracks hinder mechanical properties and transparency, limiting possible applications. Thus, we propose a filament-based deposition strategy to reduce laser power requirements. Filament-fed laser direct deposition, instead of blown powder, dramatically reduced the amount of gas porosity within the melt. Hence, highly densified, transparent, spinel ceramics were fabricated. Through decreased laser power requirements for high densification, cracking was largely reduced. This paper provides a comprehensive comparison between filament- and powder-based laser direct deposition by analyzing important sample characteristics, including porosity, cracking, grain size, and their controlling mechanisms. This paper also presents a laser direct deposition and postprocessing method to manufacture predensified spinel filaments.

Cooled SPAD array detector for low light-dose fluorescence laser scanning microscopy

The single-photon timing and sensitivity performance and the imaging ability of asynchronous-readout single-photon avalanche diode (SPAD) array detectors have opened up enormous perspectives in fluorescence (lifetime) laser scanning microscopy (FLSM), such as super-resolution image scanning microscopy and high-information content fluorescence fluctuation spectroscopy. However, the strengths of these FLSM techniques depend on the many different characteristics of the detector, such as dark noise, photon-detection efficiency, after-pulsing probability, and optical cross talk, whose overall optimization is typically a trade-off between these characteristics. To mitigate this trade-off, we present, to our knowledge, a novel SPAD array detector with an active cooling system that substantially reduces the dark noise without significantly deteriorating any other detector characteristics. In particular, we show that lowering the temperature of the sensor to −15°C significantly improves the signal/noise ratio due to a 10-fold decrease in the dark count rate compared with room temperature. As a result, for imaging, the laser power can be decreased by more than a factor of three, which is particularly beneficial for live-cell super-resolution imaging, as demonstrated in fixed and living cells expressing green-fluorescent-protein-tagged proteins. For fluorescence fluctuation spectroscopy, together with the benefit of the reduced laser power, we show that cooling the detector is necessary to remove artifacts in the correlation function, such as spurious negative correlations observed in the hot elements of the detector, i.e., elements for which dark noise is substantially higher than the median value. Overall, this detector represents a further step toward the integration of SPAD array detectors in any FLSM system.

Feedback Control of Melt Pool Area in Selective Laser Melting Additive Manufacturing Process

Selective laser melting (SLM), a metal powder fusion additive manufacturing process, has the potential to manufacture complex components for aerospace and biomedical implants. Large-scale adaptation of these technologies is hampered due to the presence of defects such as porosity and part distortion. Nonuniform melt pool size is a major cause of these defects. The melt pool size changes due to heat from the previous powder bed tracks. In this work, the effect of heat sourced from neighbouring tracks was modelled and feedback control was designed. The objective of control is to regulate the melt pool cross-sectional area rejecting the effect of heat from neighbouring tracks within a layer of the powder bed. The SLM process’s thermal model was developed using the energy balance of lumped melt pool volume. The disturbing heat from neighbouring tracks was modelled as the initial temperature of the melt pool. Combining the thermal model with disturbance model resulted in a nonlinear model describing melt pool evolution. The PID, a classical feedback control approach, was used to minimize the effect of intertrack disturbance on the melt pool area. The controller was tuned for the desired melt pool area in a known environment. Simulation results revealed that the proposed controller regulated the desired melt pool area during the scan of multiple tracks of a powder layer within 16 milliseconds and within a length of 0.04 mm reducing laser power by 10% approximately in five tracks. This reduced the chance of pore formation. Hence, it enhances the quality of components manufactured using the SLM process, reducing defects.

Effect of Cooling Method on Formability of Laser Cladding IN718 Alloy.

The finite element model (FE) of temperature field of straight thin-walled samples in laser cladding IN718 was established, and the growth of microstructure was simulated by cellular automata (CA) method through macro-micro coupling (CA-FE). The effects of different cooling conditions on microstructure, hardness, and properties of laser-cladding layer were studied by designing cooling device. The results show that the simulation results are in good agreement with the microstructure of the cladding layer observed by the experiment. With the scanning strategy of reducing laser power layer-by-layer, the addition of water cooling device and the processing condition of 0.7 mm Z-axis lift, excellent thin-walled parts can be obtained. With the increase of cladding layers, the pool volume increases, the temperature value increases, the temperature gradient, cooling rate, solidification rate, K value gradually decrease, and eventually tend to be stable, in addition, the hardness shows a fluctuating downward trend. Under the processing conditions of layer-by-layer power reduction and water cooling device, the primary dendrite arm spacing reduced to about 8.3 μm, and the average hardness at the bottom of cladding layer increased from 260 HV to 288 HV. The yield strength and tensile strength of the tensile parts prepared under forced water cooling increased to a certain extent, while the elongation slightly decreased.