Effect Of Laser Surface Treatment Research Articles

Laser surface treatment to improve mechanical properties of cast titanium

Objective The aim of this study was to investigate the effect of laser surface treatment on the mechanical properties of cast titanium and to compare with those of the Co–Cr alloy. Methods Dumbbell-shaped cast specimens were prepared for commercially pure titanium (grade 2) and Co–Cr alloy. The cast titanium specimens were laser-treated on the surface using a dental Nd:YAG laser machine at 240 V and 300 V. After laser treatment, tensile testing was conducted to obtain the tensile strength, percent elongation and modulus of elasticity. The hardness depth profile was made from the cast subsurface (25 μm) to 1500 μm in depth using the cross-sections of the cast rods with the same diameter as the dumbbell. The data were statistically analyzed by ANOVA/post hoc tests ( p < 0.05). Results The highest tensile strength was obtained for the titanium specimens laser-treated with 300 V followed by the 240 V and the control specimens. The laser-treated titanium specimens with 300 V showed a tensile strength equivalent to the Co–Cr alloy. Although the highest modulus of elasticity was found for the specimens laser-treated with 240 V, there were no significant differences in elastic modulus among 240 V, 300 V and Co–Cr. The laser-treated groups showed significantly lower hardness at the subsurface of 25 μm and maintained their hardness until the depth of 400 μm. The hardness of the control group was very high at 25 μm depth, and dramatically decreased until the 200 μm depth. Conclusion The results of tensile testing and hardness depth-profiling indicated that the laser treatment significantly improved the mechanical properties of cast titanium by improving the surface integrity of the cast surface contamination.

Corrosion Control of Friction Stir Welded Aluminium Airframe Alloy

In the present study, microstructure and its influence on corrosion behaviour of friction stir welded aluminium airframe alloy have been investigated. Further, the effect of laser surface treatment on the microstructure and the corrosion behaviour was also assessed. The welded AA2024 alloy showed the expected zones associated with friction stir welding. Corrosion testing showed that modified microstructure reduced its corrosion resistance to localized corrosion, with the regions immediately outside TMAZ being most susceptible to corrosion. Laser treatment resulted in a melted near-surface layer, up to 5 (m thick, where normal constituent particles are absent. Scrutiny of the melted near-surface layer revealed continuous segregation bands, approximately 10 nm thick, containing mainly copper. Corrosion testing showed that laser treatment increases the short term resistance to localized corrosion due to the removal constituent particles. However, prolonged testing revealed corrosion within the melted near-surface layer and delamination of the melted near-surface layer from underlying bulk alloy. The corrosion is associated with copper rich segregation bands that promote local microgalvanic action.

Effect of laser surface treatment on corrosion and wear resistance of ACM720 Mg alloy

A creep resistant Mg alloy ACM720 was subjected to laser surface treatment using Nd:YAG laser equipped with a fiber optics beam delivery system in argon atmosphere. This treatment was found to be beneficial for the corrosion and wear resistance of the alloy. Long-term linear polarization resistance and Electrochemical Impedance Spectroscopy measurements confirmed that the polarization resistance values of laser surface treated alloy were twice as high as that for the untreated alloy. The improved corrosion resistance was attributed to the absence of the second phase Al 2Ca at the grain boundary, microstructural refinement and extended solid solubility, particularly of Al, in α-Mg matrix owing to rapid solidification. The laser treatment also increased surface hardness two times and reduced the wear rate considerably due to grain refinement and solid solution strengthening.

Effect of Laser Surface Treatment on Microstructure and Properties of MRI 230D Mg Alloy

A creep resistant Mg alloy MRI 230D was subjected to laser surface treatment using Nd:YAG laser equipped with a fiber optics beam delivery system in argon atmosphere. The laser surface treatment produced a fine dendritic microstructure and this treatment was beneficial for the corrosion and wear resistance of the alloy. Long-term linear polarisation resistance and Electrochemical Impedance Spectroscopy measurements confirmed that the polarisation resistance values of laser treated material were twice as high as that for the untreated material. This improved behaviour was due to the finer and more homogenous microstructure of the laser treated surface. The laser treatment also increased surface hardness two times and reduced the wear rate by 25% due to grain refinement and solid solution strengthening.

Improving corrosion and wear performance of HVOF-sprayed Inconel 625 and WC-Inconel 625 coatings by high power diode laser treatments

This paper reports an investigation of the effects of laser surface treatment on the corrosion and wear performance for Inconel 625, and Inconel 625-based WC HVOF-sprayed MMC coatings. Examination of the laser-treated surface was conducted in terms of microstructural morphology, chemical composition and phase analysis. Corrosion resistance using potentiodynamic polarisation in 3.5% NaCl solution and dry sliding wear behavior of the various coatings before and after laser treatment was evaluated. The results indicated that significant improvement of corrosion and wear resistance can be achieved after laser treatment as a result of the elimination of discrete splat-structure, microcrevice and porosity, and also the reduction of microgalvanic driving force between the WC and the metal matrix. In addition, the formation of faceted dendritic structure of the WC phase was considered to be beneficial for the wear performance.

Review of Various Surface Treatment Techniques on Titanium Alloys and Their Protective Effects against Corrosion

This paper attempts at a review of the recent developments on the improvement of surface corrosion in titanium alloys and composites by various surface treatment techniques. The surface treatment techniques include different types of laser surface coating, plasma enhanced vapour deposition, high intensity plasma beam coating, cathodic are deposition and reactive magnetron sputtering. Also the effect of laser surface treatment on Ti-TiB composite and its corrosion resistance properties were reviewed. The possibility of laser surface modification of Ti-TiB composite surface for enhancement of corrosion properties was also reviewed and discussed.

The effects of pulsed Nd:YAG laser irradiation on surface energy of copper

The effect of laser surface treatment on the surface energy of copper plate was investigated in terms of the surface microstructure analysis and theoretical computation in this paper. The surfaces of the copper plates were treated by Nd:YAG pulsed laser with different powers. The microstructures of the treated copper plates were analyzed by optical microscopy and X-ray diffraction (XRD), and the wetting experiment was performed to evaluate the variation of surface energy. The results showed that the surface microstructure and the corresponding surface energy of copper, changed with the variation of the laser power. The experimental results further explained by XRD results and theoretical calculation, demonstrated that the surface energy changed when the crystal structure in the surface layer was re-oriented in a preferred orientation after laser irradiation.

The effects of XeCl laser etching of Ni–Cr alloy on bond strengths to composite resin: a comparison with sandblasting procedures

The aim of this study was to determine the effect of laser surface treatment of Ni-Cr alloy on the tensile bond strength of a proprietary composite resin (Panavia 21) in comparison with a conventional sandblasting technique. Eighty cylinders of Ni-Cr were randomly allocated into the following groups: Group I-sandblasting only; Group II-low laser fluence (3.0 J/cm(2)); Group III-medium laser fluence (4.0 J/cm(2)); Group IV-high laser fluence (4.9 J/cm(2)); Group V-sandblasting in combination with medium laser fluence (4.0 J/cm(2)). Specimens within groups were bonded into pairs with resin cement as per manufacturer's instructions. They were then de-bonded using a tensile test. The mean de-bond strengths (SD) were: Group I-13.1 (4.2)MPa; Group II-17.6 (5.8)MPa; Group III-25.7 (11.8)MPa; Group IV-22.6 (6.6)MPa; Group V-41.8 (13.2)MPa. A statistically significant improvement (Bonferroni, p<0.05) in bond strength was found for the specimens which had been both lased and sandblasted (Group V) compared to all other groups, including those which were only sandblasted. Laser pre-treatment of Ni-Cr alloy increases bond strength to composite resin compared with sandblasting; laser pre-treatment in combination with sandblasting further increases the de-bond strengths.

The effects of laser-induced modification of surface roughness of Al2O3-based ceramics on fluid contact angle

Laser surface treatment of Al 2 O 3 -based refractory ceramics, by melting and re-solidification, can be successfully applied to producing surfaces that are pore-free, homogeneous and crack-free. Such treated surfaces can lead to an increase in the corrosion and erosion resistances of the materials, due to lower permeability to corrosive species and higher surface hardness, respectively. Furthermore, the corrosion resistance can be influenced by the wetting characteristics of the treated surfaces in service environment. Therefore, it is important to investigate the effect of laser treatment of ceramic materials on the interaction of the surface with the various environmental elements. This work is concerned with an experimental investigation of the effects of laser surface treatment, by melting and re-solidification, on the fluid contact angles of Al 2 O 3 -based refractory ceramics. These effects are examined by the modification of the surface roughness characteristics induced by laser treatment. Laser-treated surfaces, both containing cracks and crack-free, are compared with untreated surfaces and the results are reported. The untreated surfaces demonstrated considerable non-uniformity in wetting, in contrast to the treated surfaces. The extent of wetting of the laser-treated surfaces containing cracks was proportional to laser power density. This is due to wetting being enhanced, among other factors, by surface roughness, which increased with power density. The crack-free surfaces were the most smooth and, thereby, exhibited the smallest extent of wettability variations. The reduction in wettability after the laser treatment (crack-free) may have an advantage for corrosion resistance.

The effect of laser surface treatment on stress corrosion cracking behaviour of 7075 aluminium alloy

Excimer surface treatment was conducted on 7075-T651 aluminium alloy with the aim of improving the alloy's resistance to stress corrosion cracking (SCC) when tested in a NaCl solution. Using a pulse energy of 8 J/cm 2, a laser-melted layer of about 8 μm thick was formed. Within the re-solidified laser-melted layer, the original grain boundaries of the wrought structure and most of the coarse constituent particles were removed. The grain boundaries of the re-solidified structure were found to be free from precipitates. The results of the SCC tests showed that after the 30-day immersion test, the untreated specimen was severely attacked with intergranular cracks that reached deep into the specimen; by contrast, no intergranular cracks were found in the laser-treated specimen. The form of corrosion attack in the laser-treated specimen took the form of corrosion pits instead. The electrochemical impedance measurements taken during the SCC test showed that the film resistance of the laser-treated specimen was always higher than that of the untreated specimen.

The effects of laser surface treatment on the corrosion properties of Ti-6Al-4V alloy in Hank's solution

The effects of laser surface treatment on the corrosion properties of Ti-6Al-4V alloy in Hank's solution

ＴｉＡｌ金属間化合物の高温酸化に及ぼすレーザー表面処理の効果

The effect of laser surface treatment on the resistance of high-temperature oxidation of TiAl intermetallic compound was studied using 500W CO2 gas laser equipment. The diameter of the laser spot was about 100μm and scanning was 95mm·s-1. Laser surface treatment formed a layer solidified by rapid quenching on the TiAl surface. The oxidation of TiAl at 1273 K in a pure O2 atmosphere, which followed the parabolic rate law, was reduced to less than half by laser surface treatment. Scale formed on the laser surface-treated TiAl after the oxidation experiment was thinner than that formed on nontreated TiAl and contained a continuous, dense Al2O3 layer. No such continuous Al2O3 layer was observed for scale formed on nontreated TiAl, indicating that, for laser surface-treated TiAl, the continuous Al2O3 layer in the scale acted as a diffusion species barrier, inhibiting scale growth.

Ｎｉ‐Ｙ合金層を被覆したＮｉの高温酸化に及ぼすレーザー表面処理の効果

Ｎｉ‐Ｙ合金層を被覆したＮｉの高温酸化に及ぼすレーザー表面処理の効果

Water droplet erosion of laser surface treated Ti6A14V

The work reports on the effect of laser surface treatments on the water droplet erosion resistance of a commercial alloy of nominal composition Ti6A14V. Use is made of a continuous wave CO 2 laser to melt the Ti6A14V in both inert and dilute nitrogen atmospheres. The gas composition of the atmosphere is set at either 100% Ar, 90% Ar + 10% N 2 or 80% Ar + 20% N 2 by volume. The successive intertrack overlap is set at either 50% or 75% of the surface width of a single melt track. The cumulative mass loss during water droplet erosion of the laser surface melted material decreases substantially relative to the untreated material for all processing conditions examined. The enhanced erosion resistance is attributed to increases in the surface layer microhardness as well as the resistance of the martensitic microstructure to the hydraulic penetration mechanism of erosion. The benefits of nitrogen alloying over surface melting in an inert environment are not substantial, but this may be attributed to pre-existing micro-cracks in the nitrogen alloyed surface layers.

Cavitation erosion of laser l11eltedand laser nitrided Ti–6Al–4V

AbstractThe effect of laser surface treatment on the cavitation erosion resistance of Ti–6AI–4 V is reported. Surface melting and alloying of the alloy is undertaken in a controlled atmosphere of argon, or alternatively, nitrogen diluted with argon, using a continuous wave CO2 laser. The gas composition of the atmosphere is variable, set at either 100%Ar, 90%Ar + 10%N2, or 80%Ar + 20%N2, by volume. The microstructure of the laser processed layer is martensitic when processed in pure argon and exhibits a continuous surface layer of TiN when processed in a nitrogen containing atmosphere. All material melted in an atmosphere containing nitrogen exhibits some cracking in the processed layer. The results presented demonstrate that the steady state erosion rate is significantly decreased when the material is processed in a nitrogen containing atmosphere. The enhanced erosion resistance is attributed to the nitrogen alloyed laser processed α titanium microstructure, not the continuous TiN surface layer.MST/3073

Effect of laser surface treatment on fatigue crack growth resistance in an FeMnAl austenitic steel

Laser surface treatment (LST) results in significant improvement in fatigue crack growth resistance of an FeMnAl austenitic steel. The observed benificial effect is attributed to extensive crack closure as a result of compressive residual stresses originating from LST. The structure-sensitive nature of the crack growth operative in the base microstructure at low ΔK levels (up to ∼ 40 MPa m 1 2 with LST.

Laser surface treatment and corrosion behaviour of martensitic stainless AISI 420 steel

Abstract The effect of laser surface treatment of AISI 420 steel was studied. The operation conditions of the laser treatment were optimized with regard to beam power and displacement rate in order to produce different surface microstructures. The corrosion behaviour was studied as a function of the microstructures developed in the material. Maximum hardness was observed in the non-melted and carbide-free zone which was transformed into martensite. The best corrosion behaviour was observed in completely melted areas; this behaviour is similar to that observed in the starting material which is quenched and homogeneously tempered. Heterogeneous zones exist after laser heat treatment which have to be considered for final applications.

The effect of laser surface treatments on the tribological behavior of Ti-6Al-4V

Laser surface treatments were tried with the objective of improving the tribological performance of Ti-6Al-4V. The surface treatments used were laser surface melting, laser nitriding and laser nickel alloying, which were performed using a 1.4 kW CO 2 laser. The process parameters for laser surface treatments were optimized. The microstructures produced and the compounds formed were analyzed using standard metallographic and X-ray diffraction techniques. The abrasive, erosive and sliding wear behaviors of the laser-treated surfaces were studied. It was found that, whereas laser nitriding and nickel alloying reduced abrasive wear, laser surface melting did not. The reduction in the abrasive wear rate of laser-nitrided and nickel-alloyed specimens is attributed to the formation of TiN and Ti 2Ni respectively in the molten and resolidified region. All three laser surface treatments resulted in improving the dry sliding wear resistance. This is attributed to the increased hardness as well as the formation of wear-resistant compounds in nitriding and nickel alloying. The mechanism of wear in the untreated titanium alloy was primarily ploughing but in the laser-treated cases material was removed by the formation and rupture of adhesive bonds. The increased hardness is believed to change the mechanism of sliding wear from ploughing to adhesion. It was found that the laser treatments did not have any effect on the erosion resistance of Ti-6Al-4V when impacted by coarse particles at a high velocity. The above results are supported by electron microscopy of the worn surfaces.

The Effect of Laser Surface Treatment of High-Temperature Oxidation and Corrosion Resistance of Materials and Coatings

The Effect of Laser Surface Treatment of High-Temperature Oxidation and Corrosion Resistance of Materials and Coatings