Improvement of hot forging manufacturing with PVD and DUPLEX coatings

The application of a DUPLEX treatment, which included low pressure pulsed p lasma nitriding of AISI H11 tool steel dies and PVD BALLNIT(R) FUTURA-TiN/T iAlN multilayered coating, was studied as a possible technology to improve the process of hot forging of steel components. The quality of the DUPLEX t reatment was determined by laboratory analyses of coated test plates, which were treated together with the hot forging dies. Surface roughness, Vicker s microhardness including in-depth measurements, coating thickness and adhe sion parameters determined by the REVETEST method and microanalysis (SEM an d EDS), were investigated. Performance tests were made in real working cond itions in the UNIOR hot forging industry in Zrece, Slovenia, and included t hree types of technological processes: (a) form milling of graphite electro des (to produce dies by the electrical discharge machining process with cem ented carbide cutters improved with a BALINIT(R) Diamond coating); (b) hot forging of steel components (with two step forging dies fixed in a 1650 t e ccentrically driven press, improved with the DUPLEX treatment); (c) hole pu nching in forged parts (with dies made of ASP30 tool steel and improved wit h a standard PVD TiN coating). The hole punching in forged parts and millin g of graphite electrodes were performed successfully in practice for many y ears. In hot forging, the first positive results were obtained after three experimental studies in the last two years. Optimisation of the parameters of the DUPLEX treatment is still needed before this technology can be intro duced into regular manufacturing operations for hot forged steel parts. (C) 2001 Elsevier Science B.V. All rights reserved.