Effects Of Pulsed Nd Research Articles

Effects of pulsed Nd:YAG laser kernel irradiation on maize (Zea mays L.): Insights into germination, gas exchange, photosynthetic pigments, and morphological modifications

Energy has always been the most concerned topic worldwide due to its large consumption. Among various types of energies, light has amazing characteristics and have interesting effects on living organisms. Interest is increasing in the use of laser kernel treatment as an environment friendly physical technique for better results in agronomic crops, but the work is still in progress. The present study was conducted with the aim to examine the application of range of Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) pulsed laser exposures (200, 400, 600, 800, 1000, 1200, 1400 J/cm2) as pre-sowing kernel treatment on seedling survival rate, leaf photosynthetic activity in relation with photosynthetic pigments and visual morphological effects at seedling to maturity stage. Results showed that the low laser exposure (200, 400 and 600 J/cm2) improved the photosynthetic activity in parallel with improvement in chlorophyll a, chlorophyll b, total chlorophyll, carotenoids as well as morphological traits. Kernel treatments with higher laser fluences (800, 1000, 1200 and 1400 J/cm2) showed irregular responses in studied attributes examined at the individual plant level. At 800 and 1000 J/cm2 improvements were found in some plants but at higher doses clear negative impacts were recorded on studied attributes. In conclusion, the lower doses of Nd:YAG pulsed laser fluences are found beneficial for induction of improvement in maize plants for better growth but higher doses were found toxic ones. In future further studies are needed to check the impacts of low laser doses on yield related attributes under field conditions and the high doses might also be used to create variants with beneficial characteristics if possible.

The Heat, Plasma, and Laser Treatments Characteristics of Hydroxyapatite Coatings

In this work, the study of thermal treatment by laser, plasma glow discharge, and tubular furnace on Ti-6Al-4V alloy coated with hydroxyapatite (HA) by methods of dip coating and electrophoretic deposition. The effect of pulsed Nd:YAG laser , oxygen plasma and tubular furnace treatments on structure, morphology and corrosion resistance of HA coating –Ti6Al4V alloy samples were thermal reported. The samples were tested by optical microscope, XRD, SEM, and the corrosion characteristic with open circuit potential (OCP) and polarization curve (Tafel). The results showed that the samples thermal reported by tubular furnace were the best where the corrosion rate was reduced to 3.567×10-4 mm/y for the dip-coated samples and 7.221×10-4 mm/y for the electrophoretically deposited samples compared with 9.396×10-3mm/y for uncoated sample. It was found that the heat, laser and plasma treatment enhanced the structure and corrosion resistance properties of the HA coating on Ti6Al4V substrate for use in biomedical applications. This research demonstrates a new low-cost approach to produce high corrosion resistance biocompatible materials.

Comparison of the Efficiency of High-Intensity Laser Therapy and Transcutaneous Electrical Nerve Stimulation Therapy in Patients With Symptomatic Temporomandibular Joint Disc Displacement With Reduction

Many different treatment modalities have been tried in the treatment of temporomandibular joint (TMJ) disorders and different results have been reported. The aim of the study was to investigate and compare the effects of high-intensity laser therapy (HILT) and transcutaneous electrical nerve stimulation (TENS) therapy on the treatment of patients with TMJ disc displacement with reduction(DDWR). Researchers conducted a prospective, single-blind, controlled clinical trial on patients with TMJ disc disease at a university's oral and maxillofacial surgery clinic. One hundred two patients were randomized into 3 groups (HILT, TENS and control group). The patients were evaluated in terms of maximum mouth opening (MMO), assisted MMO, Visual Analog Scale (VAS) (pain), and VAS (function). In addition, the disability status of the patients with the Jaw Functional Limitation Scale-20 (JFLS-20) and the quality-of-life with the Oral Health Impact Profile (OHIP-14) was evaluated. At the start of the trial, in terms of socio-demographic characteristics, no significant differences existed between the groups. Significant improvements were seen in pain (VAS), MMO, total JFLS-20 and total OHIP-14 scores in the HILT and TENS groups compared to the control group. At week 4, the VAS pain score decreased significantly in the HILT group compared to the TENS group (48 and 25%, respectively), while the MMO was significantly increased (24 and 10%, respectively). In addition, there was a significant improvement in both the total JFLS-20 score and the total OHIP-14 score at weeks 4 and 12 in the HILT group compared to the TENS group (P < .05). It was observed that the healing effect of pulsed Nd: YAG laser therapy was significantly higher than TENS in patients with DDWR. Therefore, HILT should be a priority option over TENS therapy in patients with disc displacement.

Hot cracking in autogenous welding of 6061-T6 aluminum alloy by rectangular pulsed Nd:YAG laser beam

Due to high hot crack susceptibility of Al-Mg-Si alloys, autogenous welding by rectangular pulsed laser beam has not been generally successful in the removal of cracks. In this research, the effect of pulsed Nd:YAG laser parameters and preheating on the creation of hot cracks in the 6061-T6 aluminum alloy was investigated. The sample that was fabricated by the laser parameters including 1 Hz, 0.12 mm/s, 10 ms, and without preheating exhibited the highest cooling rate and the smallest dendrite arm spacing but no hot crack was observed. The tensile test specimens of this sample fractured at a point far from the weld metal and a decrease in the precipitation of silicon and magnesium in the inter-dendritic space and the reduction of thermal stresses resulted in the elimination of hot cracks. However, according to macro-scale models for the creation of hot cracks, preheating decreased the tensile stresses in the BTR (brittle temperature range), but increasing the preheating temperature led to increasing rather than decreasing the hot crack length. In this case, the formation of hydrogen porosity, the segregation of silicon and magnesium, and the creation of low melting point compounds were the important parameters affecting the hot crack initiation and growth.

Laser annealing enhanced the photophysical performance of Pt/n-PSi/ZnO/Pt-based photodetectors

Herein, the effect of pulsed Nd:YAG laser irradiation at different fluencies in air at room temperature on the performance of n-PSi/ZnO-based UV MSM photodetector was demonstrated. Thermal and photon energies were coupled to synthesize n-PSi/ZnO NCs heterojunctions. The porous silicon (PSi) films with nano-sized pore arrays were first prepared via photoelectrochemical etching (PECE) of n-type silicon wafers with 45 mA/cm2 current density for a duration of 30 min. This was followed by radio frequency sputtering (RFS) of ZnO on PSi at 700 °C and irradiating with a Nd: YAG laser pulses with laser fluence of 40 mJ/cm2. X-ray diffraction analysis indicates the formation of ZnO wurtzite hexagonal crystal structure of n-PSi/ZnO NCs, where the crystallite size decreases (96–29 nm) with number of pulses. Field emission electron scanning microscopy and atomic force microscopy reveal porous nanostructure, arrays of nearly spherically shape particles homogeneously distributed on the entire surface where roughness increases (84–139 nm) with number of pulses.Photoluminescence spectroscopy reveals intrinsic band-to-band transition, donor-acceptor pair emission and quenching of the broadband intensity related to improved of crystallinity, meanwhile the band gap energy of the n-PSi/ZnO NCs is found to decrease (3.26 – 3.13 V). The Nd:YAG laser annealing demonstrate a positive effect on the properties of n-PSi/ZnO NCs photodetector, exhibiting very high sensitivity (3772.92) and very short rise and recovery times (0.30 s and 0.26 s).

Pulsed ND:YAG laser combined with progressive pressure release in the treatment of cervical myofascial pain syndrome: a randomized control trial.

[Purpose] To investigate the effect of pulsed Nd:YAG laser combined with the progressive pressure release technique (PPRT) and exercises in the treatment of myofascial trigger points (MTrPs) in patients with myofascial pain syndrome (MPS). [Participants and Methods] A total of 50 patients with MTrPs in the upper trapezius muscle participated in the study. The patients were randomly assigned to two groups and treated with laser plus PPRT (Laser + PPRT group) or placebo laser and exercises (PL + PPRT group). The laser was applied for eight MTrPs with a 50 J/point. PPRT was applied for 30 seconds for each point. Exercises included strengthening and stretching exercises applied three times per week for four weeks. A visual analogue scale (VAS) and pressure pain threshold (PPT) were used to measure pain and pain threshold, respectively. A cervical range of motion device (CROM) was used to measure the cervical range of motion. [Results] Both treatment groups showed significant improvement in CROM, PPT, and VAS post-treatment with a more significant effect in the Laser + PPRT group compared to the PL + PPRT group. [Conclusion] PPRT and exercises alone or that in combination with laser therapy were effective in the treatment of active MTrPs in patients with MPS.

Pulsed Nd:YAG laser: effects on pain, postural stability, and weight-bearing pattern in children with hemophilic ankle arthropathy.

Hemophilic ankle arthropathy features joint pain, impaired postural control, and abnormal weight-bearing pattern. This study was designed to investigate the effects of pulsed Nd:YAG laser on pain, postural stability, and weight-bearing pattern in children with hemophilic ankle arthropathy. Forty children diagnosed with hemophilia type A (age, 8-16 years) were randomly allocated to either the treatment group (n = 20) who received a three-phase active therapy with pulsed Nd:YAG laser thrice/week (total energy was 1500 J) plus a physical exercise program for four consecutive weeks, or the placebo group (n = 20) who received placebo laser plus the physical exercise program. Pain, postural control (i.e., directional control [DC], endpoint excursion [EE], center-of-gravity movement velocity [CoG-MV], and maximum excursion [MXE]), and weight-bearing pattern (i.e., pressure peaks of the hindfoot [PP-HF] and forefoot [PP-FF], and the foot contact area [FCA]) were assessed pre- and post-treatment. The treatment group showed greater improvement in pain (P = .004), DC (P = .02), EE (P = .003), and CoG-MV (P = .003) compared to the placebo group. However, there was no statistically significant difference between both groups regarding the MXE (P = .15). In addition, the treatment group achieved favorable improvements in PP-HF (P = .003), PP-FF (P = .027), and FCA (P = .002) relative to the placebo group. Pulsed Nd:YAG laser is a potentially effective therapy for pain relief, postural control enhancement, and weight-bearing pattern adjustment in children with hemophilic ankle arthropathy.

The effect of pulsed Nd:YAG laser welding parameters on defects of Kovar to AISI 304L dissimilar joint

Kovar, due to its close thermal expansion coefficient to glass, can be used as a mediating alloy in joint of glass to metals such as AISI 304L. In the present research, the effect of parameters of pulsed laser on dissimilar welding of Kovar to AISI 304L has been investigated. For observation and investigation of the results, metallography, Energy dispersive X-ray spectroscopy (EDS) and microhardness tests have been used. Results obtained from microstructural examinations, indicated the existence of solidification crack and lack of complete mixing in the weld metal. According to the results, the heat input must have an optimum value equaling approximately 19.1 J/mm. At higher levels such as 32.6 J/mm, the TCL (total crack length) value reached 760 μm. Increasing the heat input lead to increasing thermal stresses and formation of crack in the weld metal. On the other hand, at heat input levels less than the value of 15 J/mm, cracks are eliminated and non-mixing is clearly observable because sufficient time is not provided for mixing and, then, solidification for the weld metal. The weld metal hardness is also higher than the base metals due to the fine dendrite structure and the presence of hardening elements.

Long-Term Effect of Pulsed Nd:YAG Laser in the Treatment of Patients with Rotator Cuff Tendinopathy: A Randomized Controlled Trial.

The purpose of the present study was to investigate the long-term effect of pulsed Nd:YAG laser on the treatment of rotator cuff tendinopathy. Sixty patients with rotator cuff tendinopathy participated and completed the study. The mean age was 50.2 ± 3.6 years. Participants were randomly assigned to one of two groups: the control group and the treatment group. Both groups were treated with an exercise program, in addition to the pulsed Nd:YAG laser received by the treatment group and the "sham" laser received by the control group, both for three sessions per week for 4 weeks. Outcome measures included pain, assessed by the visual analog scale, and range of motion (ROM), assessed using a traditional goniometer, while the shoulder pain and disability index were used to evaluate the functional recovery of the shoulder joint. Evaluation was carried out before treatment, immediately after treatment, 3 months posttreatment, and 6 months posttreatment. Statistical analyses were used to investigate the effect of interventions and to compare the study groups' pretreatment, posttreatment, and at follow-up points. The significance level was set to p < 0.05. Pain was significantly decreased after treatment and at follow-up points, while ROM and shoulder functions were significantly improved after treatment and at follow-up intervals in both groups. The improvement was more significant in the treatment group than in the control group posttreatment and at follow-up intervals. Pulsed Nd:YAG laser combined with an exercise program seems to be more effective in the treatment of patients with rotator cuff tendinopathy than a sham laser with exercises.

Long-Term Effect of Pulsed Nd:YAG Laser in the Treatment of Children with Juvenile Rheumatoid Arthritis: A Randomized Controlled Trial.

The aim of this study was to evaluate the long-term impact of a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser [high-intensity laser therapy (HILT)] in the treatment of juvenile rheumatoid arthritis (JRA). A sample of 30 children participated in this study (15 in the laser group and 15 in the placebo group), with a mean age of 10.53 ± 1.25 years. Children who were randomly assigned to the laser group received HILT thrice per week for 4 weeks, plus the exercise program. HILT scanned each knee with 600 J in two phases and 15 J to 10 points for a total of 750 J for each knee. The placebo laser group received placebo HILT plus the same exercise program. The outcomes measured in this study were the pain level by the visual analog scale (VAS) and gait parameters by the GAITRite® system. Statistical analysis was performed by ANOVA with repeated measures to compare the differences between the baseline, post-treatment, and 12-week follow-up measurements for both groups. The level of significance was set at p < 0.05. The VAS results significantly decreased post-treatment in the laser group relative to the placebo group and were still improved at the 12-week follow-up. Gait parameters significantly increased in the laser group after 4 weeks of treatment and after 12 weeks compared to the placebo group. HILT, when combined with an exercise program, appears to be more effective in children with JRA than a placebo laser procedure with exercises.

Effects of Pulsed Nd:YAG Laser Welding Parameters on Penetration and Microstructure Characterization of a DP1000 Steel Butt Joint

Of particular importance and interest are the effects of pulsed Nd:YAG laser beam welding parameters on penetration and microstructure characterization of DP1000 butt joint, which is widely used in the automotive industry nowadays. Some key experimental technologies including pre-welding sample preparation and optimization design of sample fixture for a sufficient shielding gas flow are performed to ensure consistent and stable testing. The weld quality can be influenced by several process factors, such as laser beam power, pulse duration, overlap, spot diameter, pulse type, and welding velocity. The results indicate that these key process parameters have a significant effect on the weld penetration. Meanwhile, the fusion zone of butt joints exhibits obviously greater hardness than the base metal and heat affected zone of butt joints. Additionally, the volume fraction of martensite of dual-phase steel plays a considerable effect on the hardness and the change of microstructure characterization of the weld joint.

Efficacy of pulsed Nd:YAG laser in the treatment of patients with knee osteoarthritis: a randomized controlled trial.

The purpose of this study was to investigate the effects of pulsed Nd:YAG laser plus glucosamine/chondroitin sulfate (GCS) in patients with knee osteoarthritis (KOA) by examining changes in pain and knee function, as well as synovial thickness (ST) and femoral cartilage thickness (FCT). Sixty-seven male patients participated, with a mean (SD) age of 53.85 (4.39) years, weight of 84.01 (4.70) kg, height of 171.51 (3.96) cm, and BMI of 28.56 (1.22). Group 1 was treated with high-intensity laser therapy (HILT), GCS, and exercises (HILT + GCS + EX). Group 2 was treated with GCS plus exercises (GCS + EX), and group 3 received placebo laser plus exercises (PL + EX). The outcomes measured were pain level and functional disability using the visual analog scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), respectively. ST and FCT were measured by ultrasound examination. Statistical analyses were performed to compare differences between baseline and after 6weeks of treatment and then after 3months of follow-up. Statistical significance was set at p < 0.05. VAS and WOMAC were significantly decreased in all groups after 6weeks, with nonsignificant differences between 6weeks and 3months of follow-up. ST was significantly decreased in the HILT + GCS + EX group posttreatment, with nonsignificant decreases in the GCS + EX and PL + EX groups, as well as nonsignificant differences to FCT in all groups. Overall, pulsed Nd:YAG laser combined with GCS and exercises was more effective than GCS + EX and exercises alone in the treatment of KOA patients.

Effect of pulsed Nd:YAG laser re-melting on chromium surface alloyed AA6061-T6 aluminum

In this work, in situ formation of Al–Cr intermetallic compound on the surface of AA6061-T6 aluminum pre-placed chromium powder via pulsed Nd:YAG laser surface alloying was investigated. The effect of laser re-melting on microstructure and hardness of the treated layers was examined. Laser re-melting resulted in a significant reduction in the presence of cracks, pores, and undissolved Cr-rich particles along with a more uniform distribution of intermetallic compounds. The results showed that the alloyed layers mainly consisted of fine Al7Cr and Al4Cr intermetallic compounds in an α-Al solid solution matrix with cellular and dendritic morphologies. Hardness profiles along cross section and top surface of the alloyed layers indicated that laser re-melting enhanced homogeneity and increased the hardness value to more than six times of that of the base material.

Structure, Texture and Magnetic Properties of Laser-Welded Ultrathin Fe–Co–V Foils

This research aims to investigate the effect of pulsed Nd:YAG laser micro-welding on the microstructure, texture and magnetic properties of ultra-thin Fe–Co-7.15 wt% V magnetic alloy. Optical microscopy, scanning electron microscopy and electron backscattered diffraction techniques were used to study the microstructural evolutions. Also, vibrating sample magnetometry was used to characterize the magnetic properties. The results showed that the fractions of low Σ coincidence site lattice boundaries in the fusion zone are higher than those of the base metal. The welded samples experience a significant decrease in their magnetic properties. It was found that the formation of new fiber texture in the fusion zone and grain coarsening are the most important factors affecting the magnetic properties.

Systematic Review of the Adjunctive Use of Diode and Nd:YAG Lasers for Nonsurgical Periodontal Instrumentation

The aims of this study were (1) to conduct a literature search and systematically evaluate the additional therapeutic effects of pulsed Nd:YAG or diode laser use in patients with periodontitis, (2) to assess evidence supporting the additional benefit of laser-mediated periodontal treatment in conjunction with scaling and root planning (SRP) (not as monotherapy), and (3) to interpret the evidence presented in retrieved publications. Opinions about the additional use of diode lasers in the nonsurgical treatment of plaque-induced periodontal lesions are conflicting. The April 2011 American Academy of Periodontology's "Statement on the Efficacy of Lasers in the Non-Surgical Treatment of Inflammatory Periodontal Disease" asserted that the use of a laser as monotherapy or in addition to nonsurgical periodontal instrumentation conveyed no advantage. After initial screening, 23/77 potentially relevant articles and abstracts identified through electronic and manual searches of the MEDLINE(®)/PubMed database and the Cochrane Central Register of Controlled Trials (1990-2012) were included in this review. A meta-analysis could be performed. The results indicate that Nd:YAG or diode laser, used in an adjunctive capacity to SRP, may provide some additional benefit, in 6 month studies, compared with mechanical debridement. The results show the adjunctive benefits that diode laser treatment can provide when it is used as an adjunct to nonsurgical periodontal treatment in adults with chronic periodontitis. Further long-term, well-designed, parallel randomized clinical trials are needed to assess the effectiveness of the adjunctive use of the diode laser, as well as the appropriate dosimetry and laser settings.

Effect of Pulsed Nd:YAG Laser in the Treatment of Neuropathic Foot Ulcers in Children with Spina Bifida: A Randomized Controlled Study

This study assessed the effects of pulsed Nd:YAG laser treatment of neuropathic foot ulcers in children with spina bifida. Children with spina bifida face increased risk for developing neuropathic foot ulcers. In a randomized controlled trial, 39 children and adolescents (ages 6-15 years) with spina bifida and stage III neuropathic foot ulcers were randomly assigned to the laser group or the placebo laser group. The former received pulsed Nd:YAG laser treatments (i.e., total energy of 300-350 J during three sessions/week) plus standard wound care, and the latter received sham laser treatments plus standard wound care. Wound size and wound appearance were assessed for all patients at the beginning of the treatment, after 5 weeks, and after 10 weeks. The decrease in wound surface area at 5 and 10 weeks post- treatment was significantly greater in the laser group (i.e., 2.44 ± 0.33 and 0.29 ± 0.25 cm(2), respectively) than in the placebo group (i.e., 3.81 ± 0.18 and 3.24 ± 0.44 cm(2), respectively). Also, the decrease in the total score for the Pressure Sore Status Tool (PSST) at 5 and 10 weeks post-treatment was significantly different for the laser group (i.e., 32.76 ± 2.30 and 17.52 ± 1.66, respectively) than for the placebo group (i.e., 46.50 ± 2.12 and 38.11 ± 3.17, respectively). Treatment with pulsed neodymium:yttrium aluminum garnet (Nd:YAG) laser combined with standard wound care decreases wound size and improves wound appearance for stage III neuropathic foot ulcers in children with spina bifida.

Effects of Pulsed Nd:YAG Laser on Tensile Bond Strength and Caries Resistance of Human Enamel

This study aims to evaluate the effects of pulsed Nd:YAG laser on the tensile bond strength (TBS) of resin to human enamel and caries resistance of human enamel. A total of 201 human premolars were used in this in vitro study. A flat enamel surface greater than 4 × 4 mm in area was prepared on each specimen using a low-speed cutting machine under a water coolant. Twenty-one specimens were divided into seven groups for morphology observations with no treatment, 35% phosphoric acid etching (30 seconds), and laser irradiation (30 seconds) of pulsed Nd:YAG laser with five different laser-parameter combinations. Another 100 specimens were used for TBS testing. They were embedded in self-cured acrylic resin and randomly divided into 10 groups. After enamel surface pretreatments according to the group design, resin was applied. The TBS values were tested using a universal testing machine. The other 80 specimens were randomly divided into eight groups for acid resistance evaluation. Scanning electron microscope (SEM) results showed that the enamel surfaces treated with 1.5 W/20 Hz and 2.0 W/20 Hz showed more etching-like appearance than those with other laser-parameter combinations. The laser-parameter combinations of 1.5 W/15 Hz and 1.5 W/20 Hz were found to be efficient for the TBS test. The mean TBS value of 14.45 ± 1.67 MPa in the laser irradiated group was significantly higher than that in the untreated group (3.48 ± 0.35 MPa) but lower than that in the 35% phosphoric acid group (21.50 ± 3.02 MPa). The highest mean TBS value of 26.64 ± 5.22 MPa was identified in the combination group (laser irradiation and then acid etching). Acid resistance evaluation showed that the pulsed Nd:YAG laser was efficient in preventing enamel demineralization. The SEM results of the fractured enamel surfaces, resin/enamel interfaces, and demineralization depths were consistent with those of the TBS test and the acid resistance evaluation. Pulsed Nd:YAG laser as an enamel surface pretreatment method presents a potential clinical application, especially for the caries-susceptible population or individuals with recently bleached teeth.

Surface characterisation of ASTM F139 stainless steel marked by laser and mechanical techniques

The surfaces of implantable medical devices should present proper corrosion and mechanical resistance properties to fulfil their functions. Marking techniques are used for identification and traceability purposes but often generate surface modifications. Because surface defects affect corrosion resistance, the effects of marking processes must be investigated. This paper presents the effects of pulsed Nd:YAG laser marking techniques on the corrosion resistance of ASTM F139 austenitic stainless steel compared to that of mechanical marking techniques. The corrosion resistance was evaluated by electrochemical methods, and the surface was analysed by scanning electron microscopy with a field emission gun (SEM-FEG) coupled to an energy dispersive X-ray spectrometer. The surface characterisation showed the occurrence of microstructure variation due to the high temperatures involved in the laser melting process. Compared to the mechanical method, the laser marking technique had a deleterious effect on the resistance of ASTM F139 stainless steel to localised corrosion, increasing its susceptibility to pitting corrosion. These results were related to changes in the passive film properties, surface morphology and chemical composition.

Effects of pulsed Nd:YAG laser welding parameters and subsequent post-weld heat treatment on microstructure and hardness of AISI 420 stainless steel

Martensitic stainless steels are often used in cases where high strength and medium corrosion resistance are required. In this study, pulsed Nd:YAG laser welding of AISI 420 martensitic stainless steel is considered. Welding of samples were carried out autogenously. The spacing between samples was set to almost zero. All samples were butt welded. The effect of welding parameters such as voltage, laser beam diameter, frequency, pulse duration, and welding speed on the weld dimensions were investigated and the optimum values were obtained for the 450V voltage, 0.6mm focal diameter, 6Hz frequency, 5ms pulse duration and 1.5mm/s welding speed. Microstructure of weld pool and heat affected zone (HAZ) were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). Micro-hardness studies were also carried out. The results showed the presence of some remaining delta-ferrite in the martensitic weld structure and coarsening of M23C6 carbides in HAZ. The magnitude of hardness in the HAZ was higher than that of the weld zone. To reduce the hardness of weld and HAZ and to increase the toughness in these regions, two types of post-weld heat treatments (PWHTs) were carried out. In type 1, samples tempered for 2h. In type 2, samples austenitizied for 0.5h at 1010°C and then tempered for 2h. In order to achieve high strength and toughness, optimum temper temperatures for type 1 and 2 heat treatments were obtained for 595 and 537°C, respectively. The results showed higher toughness for type 2 than type 1.

An Investigation on the Effect of Pulsed Nd:YAG Laser Welding Parameters of Stainless Steel 1.4418

In the present study, a low average power pulsed Nd:YAG laser is used for bead-on-plate welding of low carbon steel plate. The effect of laser process parameters on the weld quality and weld bead profile, welding penetration (P), welding surface width (W) and welding pool area (A), is studied. Focal point position, welding speed, pulse duration, and energy are selected as the process variables. The formation of a keyhole and weld bead profile is found to be highly dependent on laser pulse parameters. Results show that the maximum penetration accurse when the focal point is above the surface, in pulse duration of 6 ms, welding speed of 2 mm/s and pulse energy of 16.67 J.