Surface Integrity Analisys in the Hard Turning of Cemented Steel AISI 4317

Abstract

This work was based on the surface integrity analysis of hardened steel, AISI 4317 case carburized, quenched and tempered with 58 HRC, obtained by a turning operation executed with CBN (cubic boron nitride) tool, varying three basic cutting parameters (cutting speed, feed rate and cutting depth). The surface integrity characterization was conducted analyzing the behavior of the surface roughness R a , residual stresses and with layer presence after turning. Also, the cutting forces were measured. The experimental planning used was a central composite design. The results and data were statistically treated by the Statistica software, enabling the generation of a mathematical model, relating the dependent variables with the independent variables. The roughness values R a obtained after the experiments ranged from 0.31 to 2.8 µm, providing an indication that is possible to replace grinding process by hard turning using CBN tools that could reduce machining time and costs. The hard turning process generated compressive residual stresses profiles and white layer formation, from 1.1 to 5.1 µm, on the surface of the samples. The penetration force showed the highest values for the turning forces measurements. The lowest values for the cutting parameters represented the optimized surface integrity of the AISI 4317 steel.

Cryogenic milling and formation of nanostructured machined surface of AISI 4340

“…Pu et al [20] reported that cryogenic machining reduced the grain size of AZ31B Mg alloy from 12 µm to 31 nm and remarkably improved its functional performance, including hardness, corrosion/wear resistance, and fatigue life. Branco et al [21] mentioned the presence of annealed martensite at the machined surface generated by the thermo-mechanical effect. The phase transformation or the retempering of the welded martensite of the part was dependent on the machining parameters and was due to the rapid heating and cooling caused after the machining.…”

Estudo sobre a integridade superficial do aço ABNT 4140 após a operação de torneamento

“…Outro parâmetro considerado influente sobre a rugosidade é a velocidade de corte [6,7]; esta influência ocorre provavelmente devido à temperatura. Além de reduzir a possibilidade de surgimento da aresta postiça de corte 0, o aumento inicial da velocidade de corte eleva a temperatura e tende a diminuir a resistência ao cisalhamento do material.…”

“…Já o material e o desgaste da ferramenta provocam variações nas condições de atrito entre a ferramenta e a peça modificando a geração de calor. Em geral, o desgaste da ferramenta aumenta o atrito entre sua superfície de folga e a superfície da peça recém gerada e, consequentemente, o efeito térmico, podendo induzir tensões de tração [4,6]. O material ou revestimento da ferramenta pode ou não ser benéfico dependendo dos materiais envolvidos 0.…”