Influence of EDM pulse energy on the surface integrity of martensitic steels

Rebelo, J.C; Dias, Alfredo M. P. G.; Kremer, Daniel; Lebrun, J. L.

doi:10.1016/s0924-0136(98)00082-x

Cited by 187 publications

(106 citation statements)

References 6 publications

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“…All dimensions in mm. The surface of the dog bones produced by EDM is expected to be fairly rough and to contain faults, notably a thin, brittle, hard layer (called the white layer) and a heat affected zone of up to 250 μm as observed in [21][22][23]. To minimise the influence of the surface defects and the altered grain structure after the wire EDM process, the flat surfaces of the dog bones have been polished using sand paper with very fine particles.…”

Section: Tensile Testing Of Miniature Specimensmentioning

confidence: 99%

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

Bally

Waele

Verleysen

et al. 2015

SCAD

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Abstract:Welding is a widely adopted industrial process used for joining components. A fusion weld has a highly heterogeneous microstructure and characterisation of strength heterogeneity is difficult because of the potentially large variations over a limited distance. Hardness mapping and miniature tensile tests are two distinct approaches to this problem. This paper reports on the possibilities and limitations of both techniques. Hardness mapping is a well-documented procedure as opposed to miniature tensile testing, where the dimensions of the dogbone shaped specimens are smaller than what standards prescribe. A particular challenge is the measurement of strains in such small specimens. The authors have achieved this measurement by means of Digital Image Correlation (DIC). To that end, a sufficiently fine speckling method has been developed.Keywords: heterogeneity; hardness mapping; miniature tensile testing; DIC INTRODUCTIONWelding is one of the most common joining methods due to its generally high production speed and low associated costs. It is often associated with flexibility, integrity and reliability [1]. An example application showing the economic importance of welding is pipeline installation. Costs associated to fusion welding are estimated to make up 20% of the total cost of pipe laying. These include aligning the pipe sections, cleaning and grinding, welding, checking the weld for flaws and coating the weld [2].Notwithstanding the economical appeal of welding, the localized application of heat and melting results in a high susceptibility to material discontinuities, flaws and residual stresses, whose presence may lead to structural failure and lifetime reduction. The prediction of weld flaw acceptability ('structural integrity') is hampered by the potential presence of strongly heterogeneous microstructures. Modern day weld flaw assessment ignores this heterogeneity by assuming a homogeneous weld. As such, a generally accepted method to characterise weld heterogeneity does not yet exist. STATE OF THE ARTHeterogeneity is inherent to fusion welds, because in order to melt the weld metal and fuse it with the base metal, heat has to be locally applied. For thicker sections, weldments are created in several passes (deposition of multiple layers), resulting in a variety of zones undergoing a succession of particular heat cycles. The heat cycle determines what the microstructure transforms into, each structure having a different stress-strain response. Not only the weld metal is heterogeneous due to this, but the heat affected zone (HAZ) of the base metal (heated but non-melted metal in close vicinity of the weld) also transforms.Many conventional steel welds show a hardened HAZ due to the occurrence of stronger microstructures. In contrast, a broad range of high strength low alloy steels obtain their properties from a fine grain size, resulting from a specific heat treatment, often combined with mechanical deformation. These steels may show a softened HAZ due to grain coarsening. To quantify variations ...

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Section: Tensile Testing Of Miniature Specimensmentioning

confidence: 99%

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

Bally

Waele

Verleysen

et al. 2015

SCAD

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“…The remaining melt solidifies to form an undulating terrain. The pockmarks which can be observed on surfaces are formed by entrapped gases escaping from the deposited material [12].…”

Section: Surface Topographymentioning

confidence: 99%

“…The intermediate layer is a heat-affected zone, where the heat is not high enough to cause melting, but is sufficiently high to induce micro-structural transformation in the material [12]. The depth of the recast layer and the heat-affected zone is determined by the heat sinking ability of the material and the power used for the cut.…”

Section: Affected Layersmentioning

confidence: 99%

Metallurgical alterations in the surface of steel cavities machined by EDM

et al. 2013

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The electrical discharge machining (EDM) is a process characterized by high thermal demands, which tend to cause metallurgical changes in the surface of the workpiece [1][2]. This work aims to conduct a discussion of metallurgical changes in the surface of cavities obtained by the process of EDM in the machining of steel. Several variables were employed, such as cavity depth, electrode geometry and technological parameters of the process. Thus, the goal was to identify the different metallurgical changes that can occur in the machined surfaces. The evaluation of these changes was made from metallographic analysis, measurements of microhardness and of the depth of the layer affected by process. The results of this work identified several metallurgical changes such as formation of white layer, hardness variation and change of microstructure. The occurrence of microcracks also was observed, especially in severe conditions. The greatest variations in results were caused by the change of technological parameters. However, the variation in cavity depth and the change of the electrode geometry also showed influence on the results.

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“…But sometimes, improper parameters setting during rough cutting operation may deteriorate the work surface very severely, which may not be improved considerably after one or more trim cuts (Juhr et al, 2004). Several studies have been conducted on EDM/WEDM to analyse the surface characteristics of the eroded work surfaces (Kruth et al, 1995;Kahng & Rajurkar, 1997;Rebelo et al, 1998;Lee & Li, 2003;Boujelbene et al, 2009;Veldhuis et al, 2010). All these studies explored the effect of process parameters on depth of recast layer and heat affected zone.…”

Section: Fig 1 Representation Of Wedm Processmentioning

confidence: 99%

Study of unmachined area in intricate machining after rough cut in WEDM

Jangra¹

2012

IJIEC

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Wire electrical discharge machining (WEDM) is well known process for generating intricate and complex profiles in hard metal matrix composites. But damaged surface layer with poor surface integrity is a major disadvantage of WEDM. Beside poor damaged surface layer, after rough/first cut in WEDM, some surface area remains unmachined on work surface during intricate machining such as in die cutting. This paper presents a study on unmachined surface area named as surface projection, in die cutting after rough cut in WEDM. Using scanning electron microscope images, length of unmachined surface projections have been determined. In order to minimize these surface projections from small cavities having complex geometries, trim cutting operation is the best alternative. Results show that using more than one trim cut with appropriate wire offset value, surface projections can be minimized, successfully.

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Influence of EDM pulse energy on the surface integrity of martensitic steels

Cited by 187 publications

References 6 publications

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

Metallurgical alterations in the surface of steel cavities machined by EDM

Study of unmachined area in intricate machining after rough cut in WEDM

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