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Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel

In mold making, the mold surface roughness directly affects the surface roughness of the produced part. To achieve surface roughness below 0.8 μm, the cost of surface finish is high and time-consuming. One alternative to the different grinding and polishing steps is laser polishing (LP). This study...

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Autores principales: Meylan, Bastian, Calderon, Ivan, Wasmer, Kilian
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9658362/
https://www.ncbi.nlm.nih.gov/pubmed/36363339
http://dx.doi.org/10.3390/ma15217746
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author Meylan, Bastian
Calderon, Ivan
Wasmer, Kilian
author_facet Meylan, Bastian
Calderon, Ivan
Wasmer, Kilian
author_sort Meylan, Bastian
collection PubMed
description In mold making, the mold surface roughness directly affects the surface roughness of the produced part. To achieve surface roughness below 0.8 μm, the cost of surface finish is high and time-consuming. One alternative to the different grinding and polishing steps is laser polishing (LP). This study investigates and models the LP of tool steel (X38CrMoV5-1-DIN 1.2343), typical for the mold industry, having an initial rough surface obtained by electrical discharge machining. The microstructures of the re-melted layer and heat-affected zone due to the LP process were also studied. Four parameters: the laser spot size, velocity, maximum melt pool temperature and overlapping were investigated via a design of experiments (DoE) approach, specifically a factorial design. The responses were line roughness (Ra), surface roughness (Sa), and waviness (Wa). The surface topography was measured before and after the LP process by white light profilometer or confocal microscopy. DoE results showed that the selected factors interact in a complex manner, including the interactions, and depend on the responses. The DoE analysis of the results revealed that the roughness is mainly affected by the velocity, temperature and overlap. Based on a first DoE model, an optimization of the parameters was performed and allowed to find optimum parameters for the LP of the rough samples. The optimum conditions to minimize the roughness are a spot size of 0.9 mm, a velocity of 50 mm/s, a temperature of 2080 °C and an overlap of 90%. By using these parameters, the roughness could be reduced by a factor of almost 8 from 3.8 µm to approximately 0.5 µm. Observations of the microstructure reveal that the re-melted layer consists of columnar grains of residual austenite. This can be explained by the carbon intake of the electro-machined surface that helps stabilize the austenitic phase.
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spelling pubmed-96583622022-11-15 Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel Meylan, Bastian Calderon, Ivan Wasmer, Kilian Materials (Basel) Article In mold making, the mold surface roughness directly affects the surface roughness of the produced part. To achieve surface roughness below 0.8 μm, the cost of surface finish is high and time-consuming. One alternative to the different grinding and polishing steps is laser polishing (LP). This study investigates and models the LP of tool steel (X38CrMoV5-1-DIN 1.2343), typical for the mold industry, having an initial rough surface obtained by electrical discharge machining. The microstructures of the re-melted layer and heat-affected zone due to the LP process were also studied. Four parameters: the laser spot size, velocity, maximum melt pool temperature and overlapping were investigated via a design of experiments (DoE) approach, specifically a factorial design. The responses were line roughness (Ra), surface roughness (Sa), and waviness (Wa). The surface topography was measured before and after the LP process by white light profilometer or confocal microscopy. DoE results showed that the selected factors interact in a complex manner, including the interactions, and depend on the responses. The DoE analysis of the results revealed that the roughness is mainly affected by the velocity, temperature and overlap. Based on a first DoE model, an optimization of the parameters was performed and allowed to find optimum parameters for the LP of the rough samples. The optimum conditions to minimize the roughness are a spot size of 0.9 mm, a velocity of 50 mm/s, a temperature of 2080 °C and an overlap of 90%. By using these parameters, the roughness could be reduced by a factor of almost 8 from 3.8 µm to approximately 0.5 µm. Observations of the microstructure reveal that the re-melted layer consists of columnar grains of residual austenite. This can be explained by the carbon intake of the electro-machined surface that helps stabilize the austenitic phase. MDPI 2022-11-03 /pmc/articles/PMC9658362/ /pubmed/36363339 http://dx.doi.org/10.3390/ma15217746 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Meylan, Bastian
Calderon, Ivan
Wasmer, Kilian
Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel
title Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel
title_full Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel
title_fullStr Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel
title_full_unstemmed Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel
title_short Optimization of Process Parameters for the Laser Polishing of Hardened Tool Steel
title_sort optimization of process parameters for the laser polishing of hardened tool steel
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9658362/
https://www.ncbi.nlm.nih.gov/pubmed/36363339
http://dx.doi.org/10.3390/ma15217746
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