Identification of the relations between the process conditions and the forging tool wear by combined experimental and numerical investigations

Abstract

The research of the wear of a punch used to forge a cover-type forging proved a dominance of different destructive mechanisms in the particular areas of the tools. The preliminary analysis, based on many years of verified experience of the authors, showed that, in most of the working part of the forging tool, especially in flat front area, there are various degradation mechanisms, such as: thermo-mechanical fatigue, plastic deformation and material spalling, which are critical and whose share is difficult to estimate. While in the different working surface of this tool, like in radii, it can be assumed that the dominant mechanism of destruction is only abrasive wear. In both of these areas, the loss of the material was dependent on the contact conditions (the main are: stresses, temperature, friction and lubrication conditions) between the forged material and the tool, as well as the geometry of both. The obtained analysis outcomes have been confirmed for tools after forging: 6000, 9000 and 12,000 forgings; for each number of cycles, three tools were used to ensure repeatability of the operating results. The progressing geometry change of the tools as effect of material loss (determined by repeatedly by verified the 3D reverse scanning method) was presented in the form of a diagram, depending on the number of the forged elements, which resembles the classic (Lorentz) wear curve for flat front area and an almost linear wear curve for radii area with only abrasive wear. The research perfomed by means of numerical modeling confirmed that, in the last period of the tools’ operation, a drop of wear intensity is visible.