Laser interference patterned ta-C-coated dry forming tools

Abstract

Purpose This study aims to introduce a strategy that permits well-defined contact areas in forming tools for improving both wear and friction properties by a selective laser treatment of a hydrogen-free diamond-like carbon layer (DLC), for substituting lubrication in forming processes. The need of lubricant substitution in forming processes is given because, besides the positive technological aspects, lubrication leads to numerous negative economic and ecological effects such as lubricant appliance and removal costs as well as its disposal. Design/methodology/approach Hydrogen-free DLCs with an sp³-ratio of 60-70 per cent are deposited on steel surfaces and subsequently micro-structured using direct laser interference patterning (DLIP). To find the optimal structure parameters for reducing friction and wear, line-like and cross-like patterns with three different structure sizes were fabricated onto the DLC layer. Tribological measurements are performed with a ball-on-disk tribometer on the differently DLIP-structured surfaces and compared to polished steel and unstructured DLC reference surfaces. Findings A reduction of the coefficient of friction, from 0.18 to 0.11, is observed for the laser-structured DLC surfaces, reaching values comparable to lubricated and polished steel surfaces, with a friction coefficient of 0.10. Originality/value Using DLIP, it was possible to show how this method can reduce friction on DLC-coated specimens. The observed characteristics are relevant to improve the tribological performance of forming processes, without usage of lubrication.