Effects of plasma nitriding and nitrocarburizing thermochemical treatments and surface texture on surface damage evolution of hot stamping punches

Abstract

Surface texture of stamping tools affects the performance of the tool, tool life, and surface quality of the stamped product. In this work, punch samples were machined after heat treatment by milling and turning strategies in super finish processes and part of the punches were submitted either to plasma nitriding or nitrocarburizing treatment before the experiments using hot stamping of washers, which were made in two stages. Based on roughness results, for non-treated punches, most of the milled punches presented more intense surface damage than turned punches after hot stamping process, possibly due to the marks left by machining processes, affecting mechanical obstacles to wear evolution and lubricant retention on punch surface. For nitrided punches, surface damage was less intense than it was on non-treated punches. Parallel contours strategy and turning upward strategy presented less intense surface damage after the hot stamping process. For nitrocarburized punches, surface damage was less intense than it was to non-treated punches, mainly for milling strategies. SEM images of nitrided and nitrocarburized punches suggested alveolar corrosion occurrence during hot stamping process for circular upward strategy.