Thermal cracking behavior of multi-layer LAFAD coatings on nitrided die steels in liquid aluminum processing

Kulkarni, K; Srivastava, Amit Kumar; Shivpuri, Rajiv; Bhattacharya, R. S.; Dixit, Satish; Bhat, Deepak

doi:10.1016/s0257-8972(01)01452-9

Cited by 23 publications

(9 citation statements)

References 3 publications

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“…At accumulated fluences per trace above 540 J/cm 2 almost the whole spot diameter is molten, a crater appears in the center of the traces, and it can be observed the presence of a laser generated plasma when the traces are performed. 19,20 Then, the formation of larger cracks under these conditions could be attributed to: ͑1͒ the stress developed by a thicker heat affected layer and ͑2͒ the growth of initially small cracks by submitting the material to successive thermal cycles. Although the effects of a single laser trace have been described above, the result of overlapping them is considerably different and it strongly depends on the degree of overlapping.…”

Section: Resultsmentioning

confidence: 99%

Laser surface processing of titanium in air: Influence of scan traces overlapping

Pino

Serra

Morenza

2003

Journal of Laser Applications

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Laser surface treatments of titanium in air have been performed through a pulsed Nd:yttrium–aluminum–garnet (λ=1.064 μm) laser. Several samples have been obtained modifying the laser scan velocity and partial overlapping of consecutive traces, in order to study the influence of these parameters on the surface morphology. Scanning electron microscopy and profilometry measurements have revealed different surface morphologies depending on the physical processes involved in the treatments. The surfaces are melted in all cases and present a different crack configuration depending on the melting regime. In addition, at low scan velocities, the presence of a laser generated plasma results in a periodic groove structure that evolve to a flat and porous surface when the distance between traces is decreased.

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Section: Resultsmentioning

confidence: 99%

Laser surface processing of titanium in air: Influence of scan traces overlapping

Pino

Serra

Morenza

2003

Journal of Laser Applications

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“…Furthermore, in the light of the enhanced crack initiation shown by monolayer coatings, 4,9 better TF properties seem to be attainable using multilayered coatings. 5 The surface of the sample showed evident traces of delamination after 360 cycles. The initiation of thermal cracks exposes the steel to rapid oxidation which, in turn, promotes the loss of interface adhesion and spalling of the coating (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…On the other side, multilayer coating were claimed to show much better resistance to thermal cracking due to the higher crack arrest fracture toughness related to the high number of interfaces. 5 After short TF cycling (120 cycles) the use of gas nitriding also gave poor results, showing more numerous and deeper cracks than plain tool steel. In 300-500 mm deep nitrided cases cracks easily propagated throughout the entire diffusion layer of nitrided and duplex coated samples, confirming results obtained by other authors.…”

Section: Introductionmentioning

confidence: 99%

“…6 Indeed, heat checking was much less pronounced in shallow nitrided samples (100-150 mm case depth) and plasma nitrided samples, showing a more homogeneous microstructure than gas nitrided ones. 5,7 Spies et al 8 ascribed the better TF resistance of nitrided H11 and H13 than plain steel to the higher tempering resistance and hot yield strength of nitrided layers.…”

Section: Introductionmentioning

confidence: 99%

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Influence of heat treatment and surface engineering on thermal fatigue behaviour of tool steel

Pellizzari

Ugues

Cipolloni

2013

International Heat Treatment and Surface Engineering

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Thermal fatigue (TF) is a common problem in many tool steel components. It is caused by thermal cycling in presence of internal constraints. The resulting thermomechanical stresses induce thermal cracking (heat checking). A laboratory test was developed to reproduce TF damage on a laboratory scale, under oxidizing conditions. Two different test configurations were used to induce unidirectional and bidirectional cracking. Nitriding impairs TF resistance of plain steel due to the easier propagation of cracks through the diffusion layer. The efficacy of PVD coatings is dependent on their oxidation resistance and microstructure. The higher oxidation resistance of AlCrN/AlTiN than CrN results in delayed crack initiation. TF resistance is increased if the coating is free of defects and the interface adhesion is good.

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“…Hence, the thicker and dense compound layers of LPN treated specimens showed the better thermal fatigue properties was proved. In addition, crack propagation is retarded when the cracks encounter a material with sufficiently high toughness, 22,23) a thicker compound layer will make the surface more hard and brittle. 24) Non-homogeneous areas such as porous areas or cracks in the compound layer are pathways connected between the test environment and substrate through the nitrocarburized layer.…”

Section: Discussionmentioning

confidence: 99%

Thermal Fatigue Behavior of Nitrocarburized and Low Pressure Nitrided Modified JIS SKD61 Hot Work Mold Steel

Yeh

Chiu

et al. 2013

Mater. Trans.

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A novel method using induction heating equipment was employed to investigate the thermal fatigue behaviors of two hot-work steels, JIS SKD61 and modified JIS SKD61, vacuum hardened treated to 45 HRC. Selected specimens, austenitized at 1298 K for 25 min, gas quenched to room temperature and tempered at 873 K, were salt bath nitrocarburized at 843 K for 80 min and low pressure nitrided at 813 K for 6 h, respectively. Microstructure, microhardness, X-ray diffraction and thermal fatigue tests were conducted. The results show that the thermal fatigue properties of the 898 K tempered specimen were better than those of other treated specimens. The reason is that the hardened processes would give high tensile strength, which improved the tool material thermal fatigue resistance. The thermal fatigue properties of modified JIS SKD61 specimen, including mean crack length and crack distribution density, were better than those of JIS SKD61 specimen. Low pressure nitriding treatment with a homogeneous nitrided layer could better maintain thermal fatigue resistance than the nitrocarburized steel.

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Thermal cracking behavior of multi-layer LAFAD coatings on nitrided die steels in liquid aluminum processing

Cited by 23 publications

References 3 publications

Laser surface processing of titanium in air: Influence of scan traces overlapping

Laser surface processing of titanium in air: Influence of scan traces overlapping

Influence of heat treatment and surface engineering on thermal fatigue behaviour of tool steel

Thermal Fatigue Behavior of Nitrocarburized and Low Pressure Nitrided Modified JIS SKD61 Hot Work Mold Steel

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