Research On Surface Integrity Of Multi-axis Ball End Milled H13 Steel And Its Directional Effect

AISI H13 is a kind of hot work die steel which is widely used at home and abroad. Considering the severe working conditions, such as high temperature, high pressure and high impact, good surface integrity, high fatigue and wear resistance is essential for hot work dies. Multi-axis CNC Machining is an effective way widely used in aviation, aerospace, automotive, mold and other field of manufacturing. Therefore, it has important theoretical and application value to investigate the influence of multi-axis machining process on the surface integrity, fatigue performance and friction and wear properties of H13 steel.The influence mechanism of ball end milling parameters on the scallop height was analyzed. In addition, a multi-axis ball end milling H13 steel single factor experiment was conducted to study the influence of cutting tool postures, tool paths, radial depth of cut and feed per tooth on machined surface roughness, residual stress and microhardness.The mechanism and influence of metal fatigue were also analyzed. Three point bending fatigue tests were carried out to study the cutting parameters on the fatigue life using the samples obtained from five-axis ball end milling process. In addition, the typical fatigue fracture topography was analyzed macroscopically and microscopically.Influences of multi-axis milling parameters on H13 steel fatigue performance were researched. The results showed that tool paths perform an important effect on fatigue performance. A longer fatigue life is possible when the tool path is parallel to the direction of tensile force applied on the machined surface. However, fatigue life becomes poor when the two directions are perpendicular. Influences of parameters on fatigue performance are inconsistent under different tool paths. Finally, a machining process method was proposed based on the experimental investigations.Dynamic friction coefficients of the machined surfaces under different ball end milling parameters were acquired through reciprocating ball-on-disk friction tests and few conclusions can be summarized. First, friction coefficients are relatively lower and wear degree is slighter on condition that the tool path direction is perpendicular to the sliding direction. Second, the surface friction coefficients are highest when the angle between the tool path and the sliding direction equals to 45°. Last, impacts of parameters on friction coefficient are discrepant under different tool paths.