Experimental Investigation of Laser Surface Transformation Hardening of 4340 Steel Spur Gears

Borki, Al Khader; Ouafi, Abderrazak El; Chebak, Ahmed

doi:10.3390/jmmp3030072

Cited by 6 publications

(1 citation statement)

References 27 publications

(15 reference statements)

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“…Laser surface hardening is a process to increase the hardness of the surface layer and introduce the compressive residual stress, which further improve the wear resistance as well as fatigue strength of a hardenable steel. After decades of investigations, laser hardening has been well used in the industry, for example in spur gears [8] and splined shafts [9].…”

Section: Introductionmentioning

confidence: 99%

Process Signature for Laser Hardening

Frerichs

Lübben

et al. 2021

Metals

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During many manufacturing processes for surface treatment of steel components heat will be exchanged between the environment and the workpiece. The heat exchange commonly leads to temperature gradients within the surface near area of the workpiece, which involve mechanical strains inside the material. If the corresponding stresses exceed locally the yield strength of the material residual stresses can remain after the process. If the temperature increase is high enough additionally phase transformation to austenite occurs and may lead further on due to a fast cooling to the very hard phase martensite. This investigation focuses on the correlation between concrete thermal loads such as temperature and temperature gradients and resulting modifications such as changes of the residual stress, the microstructure, and the hardness respectively. Within this consideration the thermal loads are the causes of the modifications and will be called internal material loads. The correlations between the generated internal material loads and the material modifications will be called Process Signature. The idea is that Process Signatures provide the possibility to engineer the workpiece surface layer and its functional properties in a knowledge-based way. This contribution presents some Process Signature components for a thermally dominated process with phase transformation: laser hardening. The target quantities of the modifications are the change of the residual stress state at the surface and the position of the 1st zero-crossing of the residual stress curve. Based on Finite Element simulations the internal thermal loadings during laser hardening are considered. The investigations identify for the considered target quantities the maximal temperature, the maximal temperature gradient, and the heating time as important parameters of the thermal loads.

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Section: Introductionmentioning

confidence: 99%

Process Signature for Laser Hardening

Frerichs

Lübben

et al. 2021

Metals

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Effects of laser process parameters on the hardness profile of AISI 4340 cylindrical samples: statistical and experimental analyses

Bensalem

Barka

Karganroudi

et al. 2022

Int J Adv Manuf Technol

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In the present paper, continuous Nd:YAG laser hardening of cylindrical AISI 4340 steel specimens was studied using experimental and statistical analyses. Three Laser parameters namely laser power, laser feed speed, and sample rotation speed were selected to evaluate their in uence on the depth of the hardened zone, and the maximum surface hardness. Mathematical models were developed as a function of these three parameters and the analysis of variance (ANOVA) was used to conduct the statistical study. Microhardness measurements revealed three distinct regions in the heat-affected zone (HAZ) of all samples. The hardened zone (Z 1 ) near the surface with the highest value of hardness, the hardness loss zone (Z 2 ) where hardness started to decrease, and the overheated zone (Z 3 ) adjacent to the core with hardness values that were less than the base metal. Based on experimental measurements, a maximum surface hardness of 60.8 HRC was attained. Furthermore, the maximum depth of the hardened zone was observed as 500 µm. The microstructures of laserhardened samples were studied using optical and scanning electron (SEM) microscopies. The hardened region seemed to have hard martensitic microstructure. By comparing the predicted and measured data for maximum microhardness values it was revealed that the models represent the experimental values with correlations close to 100%.

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