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| 2. |
- Basu, A., et al.
(författare)
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Laser surface hardening of austempered (bainitic) ball bearing steel
- 2007
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Ingår i: Scripta Materialia. - 1359-6462 .- 1872-8456. ; 56:10, s. 887-890
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Tidskriftsartikel (refereegranskat)abstract
- This study concerns laser surface hardening (LSH) of austempered SAE 52100 steel to enhance hardness and wear resistance. Following LSH with selected laser parameters, surface microstructure and mechanical properties were evaluated by optical/scanning electron microscopy, X-ray diffraction, hardness measurement and wear studies, and thermal profile modeling. The results suggest that LSH could develop residual compressive stress and high hardness and wear resistance in this steel without affecting the bainitic core. © 2007 Acta Materialia Inc.
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| 3. |
- Rajasekaran, B., et al.
(författare)
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Effect of detonation gun sprayed Cu-Ni-In coating on plain fatigue and fretting fatigue behaviour of Al-Mg-Si alloy
- 2006
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Ingår i: Surface & Coatings Technology. - 0257-8972 .- 1879-3347. ; 201:3-4, s. 1548-1558
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Tidskriftsartikel (refereegranskat)abstract
- Detonation gun spray technique was employed to coat Al-Mg-Si alloy (AA 6063) specimens with Cu-Ni-In powder. Coated samples were characterized with reference to the microstructure, porosity, residual stresses, microhardness and surface roughness. Plain fatigue (without fretting) and fretting fatigue tests were carried out at room temperature on uncoated and coated specimens. The detonation gun spray process resulted in a dense coating of almost uniform deposition with low porosity (0.3%) and good adhesion between the substrate and the coating. Under plain fatigue loading 40 mu m thick coated samples exhibited superior lives compared with uncoated and 100 mu m thick coated specimens due to the presence of higher surface compressive residual stress in the former. Delamination-induced failure resulted in inferior lives of 100 mu m thick coated specimens. Under fretting fatigue deformation 40 mu m thick coated specimens exhibited superior lives compared with 100 mu m thick coated samples owing to higher compressive residual stress at the surface and better interfacial adhesion. At 120 MPa stress level 40 pm thick coated specimens exhibited superior fretting fatigue life compared with uncoated sample and at stress levels above 120 MPa the converse was true. This was attributed to interface cracking at higher stress levels. (c) 2006 Elsevier B.V. All rights reserved.
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| 4. |
- Rajasekaran, B., et al.
(författare)
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Effect of grinding on plain fatigue and fretting fatigue behaviour of detonation gun sprayed Cu-Ni-In coating on Al-Mg-Si alloy
- 2009
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Ingår i: International Journal of Fatigue. - 0142-1123 .- 1879-3452. ; 31:4, s. 791-796
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Tidskriftsartikel (refereegranskat)abstract
- Uniaxial plain fatigue and fretting fatigue tests were carried out on detonation gun sprayed Cu-Ni-In coating on Al-Mg-Si alloy samples, The samples in three conditions were considered: uncoated, as- coated and ground after coating. Ground coated specimens exhibited superior plain fatigue and fretting fatigue lives compared with uncoated and as-coated specimens. The life enhancement has been discussed in terms of surface finish and residual compressive stresses at the surface. (C) 2008 Elsevier Ltd. All rights reserved.
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| 5. |
- Rajasekaran, B., et al.
(författare)
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Effect of microarc oxidised layer thickness on plain fatigue and fretting fatigue behaviour of Al-Mg-Si alloy
- 2008
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Ingår i: International Journal of Fatigue. - 0142-1123 .- 1879-3452. ; 30:7, s. 1259-1266
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to investigate the performance of microarc oxide coatings of two different thicknesses (40 and 100 mu m) on Al-Mg-Si alloy samples under plain fatigue and fretting Fatigue loadings. Tensile residual stress present in the substrate of 40 mu m thick coated samples induced early crack initiation in the substrate and so their plain fatigue lives were shorter than those of untreated specimens. Presence of more pores and tensile surface residual stress in 100 mu m thick coated samples caused early crack initiation at the surface leading to their inferior plain fatigue lives compared with 40 mu m thick coated samples. While the differences between the lives of coated and uncoated specimens were significant under plain fatigue loading, this was not the case under fretting fatigue loading. This may be attributed to relatively higher surface hardness of coated specimens. The performance of 40 mu m thick coated samples was better than that of 100 mu m thick coated specimens under both plain fatigue and fretting fatigue loadings. (C) 2007 Elsevier Ltd. All rights reserved.
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| 6. |
- Rajasekaran, B., et al.
(författare)
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Influence of detonation gun sprayed alumina coating on AA 6063 samples under cyclic loading with and without fretting
- 2008
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Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 41:4, s. 315-322
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Tidskriftsartikel (refereegranskat)abstract
- The influence of detonation gun sprayed alumina coating on Al-Mg-Si alloy (AA 6063) test samples subjected to cyclic loading with and without fretting was studied in the present work. Coated samples were grounded to have coatings of two different thickness values, 40 and 100 mu m. Both 40- and 100-mu m-thick coated specimens experienced almost the same but slightly higher friction force compared with uncoated samples. Under plain fatigue loading, 100 pm coated specimens exhibited inferior lives due to the presence of lower surface compressive residual stress compared with uncoated and 40-mu m-thick coated samples. Under fretting fatigue loading, uncoated specimens exhibited inferior lives compared with coated samples owing to the very low hardness of the uncoated specimens (80 against 1020 HV0.2). The reason for the superior fretting fatigue lives of 40-mu m-thick coated samples compared with 100-mu m-thick coated samples was the presence of relatively higher surface compressive residual stress in 40-pm-thick coated specimens. (c) 2007 Elsevier Ltd. All rights reserved.
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| 7. |
- Rajasekaran, B., et al.
(författare)
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Performance of plasma sprayed and detonation gun sprayed Cu-Ni-In coatings on Ti-6Al-4V under plain fatigue and fretting fatigue loading
- 2008
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Ingår i: Materials Science & Engineering. - 0921-5093 .- 1873-4936. ; 479:1-2, s. 83-92
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Tidskriftsartikel (refereegranskat)abstract
- Cu-Ni-In powder was coated on Ti-6Al-4V fatigue test samples using plasma spray and detonation gun (D-gun) spray processes. Coatings were characterized in terms of microstructure, porosity, microhardness, residual stresses and surface roughness. Uniaxial plain fatigue and fretting tests were carried out at room temperature on uncoated and coated specimens. D-gun sprayed coating was dense with lower porosity compared with the plasma sprayed coating. D-gun sprayed coating was harder than the plasma sprayed coating and substrate because of its higher density and cohesive strength. Surfaces were very rough in both the coatings. While D-gun sprayed coating surface had higher compressive residual stresses, plasma sprayed coating surface exhibited lower values of compressive residual stresses and even tensile residual stresses. The ill effect of surface roughness was overcome by the beneficial influence of higher compressive residual stresses on the surface and higher surface hardness and so the D-gun sprayed samples exhibited superior plain fatigue lives compared with uncoated specimens. Though the plasma sprayed samples had relatively lower hardness, higher surface roughness and almost similar values of residual stresses on the surface compared with the uncoated specimens, they exhibited longer plain fatigue lives. This may be attributed to the layered structure of the coating. Though D-gun sprayed samples experienced higher friction forces, they exhibited superior fretting fatigue lives due to the presence of higher compressive residual stresses, higher surface hardness and higher surface roughness compared with uncoated specimens. The very rough surface of plasma sprayed samples enhanced their fretting fatigue lives compared with the uncoated samples. Higher surface hardness and higher compressive residual stress of the D-gun sprayed specimens were responsible for their superior fretting fatigue lives compared with the plasma sprayed specimens. (c) 2007 Elsevier B.V. All rights reserved.
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| 8. |
- Raman, S. G. S., et al.
(författare)
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Influence of substrate material on plain fatigue and fretting fatigue behavior of detonation gun sprayed Cu-Ni-In coating
- 2007
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Ingår i: Journal of thermal spray technology (Print). - 1059-9630 .- 1544-1016. ; 16:4, s. 571-579
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Tidskriftsartikel (refereegranskat)abstract
- Cu-Ni-In coating was formulated on two substrate materials-Ti-alloy (Ti-6Al-4V) and Al-alloy (AA 6063) fatigue test specimens using detonation gun (D-gun) spray process. Coating on both substrates was dense with low porosity, high hardness, and high surface roughness. Relatively higher surface compressive residual stress was present at the coating on Ti-alloy specimens. In case of the coating on Al-alloy samples, tensile residual stress was also present in some places. Uniaxial plain fatigue and fretting fatigue experiments were conducted on uncoated and coated specimens. The detrimental effect of life reduction due to fretting was relatively larger in the Al-alloy compared to the Ti-alloy. While Cu-Ni-In coating was found to be beneficial on the Ti-alloy, it was deleterious on the Al-alloy substrate under both plain fatigue and fretting fatigue loading. The results were explained in terms of differences in the values of surface hardness, surface roughness, surface residual stress, and friction stress.
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| 9. |
- Thawari, G., et al.
(författare)
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Influence of process parameters during pulsed Nd : YAG laser cutting of nickel-base superalloys
- 2005
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Ingår i: Journal of Materials Processing Technology. - 0924-0136 .- 1873-4774. ; 170:1-2, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- Although CO2 lasers have been widely employed for commercial sheet metal cutting operations, increased recognition of the processing benefits afforded by pulsed Nd:YAG lasers has recently fuelled interest in the latter. Pulsed Nd:YAG laser cutting differs from conventional continuous wave laser cutting as it involves overlapping of a series of individual spots generated by each pulse. In this paper, a typical cutting regime for pulsed Nd:YAG laser cutting of 1 mm thick Hastelloy-X sheet has been constructed and explained in terms of extent of spot overlap. The characteristics of single holes drilled employing the same process parameters as those employed for cutting were investigated and correlated with the obtained processing regime. Additionally, the influence of key process parameters like pulse duration on the shift in the constructed processing regime was investigated. Cut quality attributes like kerf width, cut edge kerf profile and surface roughness were also studied and their dependence on process parameters has been discussed. © 2005 Elsevier B.V. All rights reserved.
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| 10. |
- Bandyopadhyay, S., et al.
(författare)
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A statistical approach to determine process parameter impact in Nd : YAG laser drilling of IN718 and Ti-6Al-4V sheets
- 2005
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Ingår i: Optics and lasers in engineering. - 0143-8166 .- 1873-0302. ; 43:2, s. 163-182
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Tidskriftsartikel (refereegranskat)abstract
- The numerous unique advantages afforded by pulsed Nd:YAG laser systems have led to their increasing utility for producing high aspect ratio holes in a wide range of materials. Notwithstanding the growing industrial acceptance of the technique, the increasingly tighter geometrical tolerances and more stringent hole quality requirements of modern industrial components demand that "defects" such as taper, recast, spatter etc., in laser-drilled holes are minimized. Process parameters like pulse energy, pulse repetition rate, pulse duration, focal position, nozzle standoff, type of gas and gas pressure of the assist gas are known to significantly influence hole quality during laser drilling. The present study reports the use of Taguchi design of experiments technique to study the effects of the above process variables on the quality of the drilled holes and ascertain optimum processing conditions. Minimum taper in the drilled hole was considered as the desired target response. The entire study was conducted in three phases:(a) screening experiments, to identify process variables that critically influence taper in laser drilled holes, (b) Optimization experiments, to ascertain the set of parameters that would yield minimum taper and (c) validation trials, to assess the validity of the experimental procedures and results. Results indicate that laser drilling with focal position on the surface of the material being drilled and employing low level values of pulse duration and pulse energy represents the ideal conditions to achieve minimum taper in laser-drilled holes. Thorough assessment of results also reveals that the laser-drilling process, optimized considering taper in the drilled hole as the target response, leads to very significant improvements in respect of other hole quality attributes of interest such as spatter and recast as well. © 2004 Elsevier Ltd. All rights reserved.
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