Análise Experimental do Microfresamento no Aço H13 Laminado e Manufaturado pelo Processo de Deposição por Energia Direcionada

Abstract

Micromilling is a high-precision machining technique that stands out for its ability to produce parts with complex geometries and high-quality surface finishes. However, applying this technique to materials like H13 steel, which exhibits specific hardness and wear resistance characteristics, requires a detailed analysis of cutting conditions and material behavior during the process. This study experimentally investigated the micro-milling process of H13 steel for tools, both laminated and additively manufactured using Directed Energy Deposition (DED). The laminated steel was annealed and exhibited a hardness of 188 HV. The additively manufactured material was thermally treated for stress relief to achieve a hardness of 50 HRC and then tempered and quenched to reduce the hardness to 47 HRC. The tests consisted of machining 40 µm deep micro-channels using 400 µm diameter TiAlN-coated micro-mills. A CNC machine tool with a maximum spindle speed of 60,000 rpm and a resolution of 0.1 µm was used. For all tests, the cutting depth was 10 µm, and abundant lubrication was applied using a pulsed jet at 6 bar. Three cutting speeds, 20, 31, and 50 m/min, were used. The porosity in the micro-milled material was verified, providing a better understanding of the DED process. The effect of cutting speed on surface roughness was analyzed using ANOVA. Surface roughness was measured using a contact profilometer with a resolution of 0.16 nm. Scanning electron microscope images of the machined surfaces were also analyzed. The results showed a difference in performance between the materials. Although the additively manufactured material had higher hardness, the stress relief results were very close to those of the laminated material. Furthermore, these results showed that the wear of the cutting tool edge is significantly high, especially in the conditions produced by DED, where the high energy used, and thermal treatments confer to the material a higher resistance to deformation. This results in an increase in cutting force and accelerates tool wear throughout the process. Additionally, it was observed that the hardness of conventionally laminated material, which exhibits more ductile characteristics, is reflected in elastic deformations and burr formation.