Improvement of hot-working processes with PVD coatings and duplex treatment

Optimisation of manufacturing processes in mechanical engineering which inv olve working temperatures higher than 600 degreesC and high surface loads, e.g. pressure die-casting, hot extrusion and hot forging, is today under in tensive investigation worldwide. Traditional production procedures and the enormous quantities of products in these industries are serious limitations to the introduction of any kind of improvement to moulds, tools and dies w ith PVD coatings and duplex treatment. Thus, the simulation of selected tri bo-systems is practically impossible and any performance testing of new tec hnologies must therefore be carried out in real industrial manufacturing. I n this paper we discuss the properties of surface improvements relevant to these topics, These comprise PVD CrN, TiAlN and FUTURA TiN/TiAlN multilayer coatings, and duplex treatments, including plasma nitriding (PN) and all t hree PVD coatings. We studied the applications of CrN, PN + CrN and PN + Ti AlN in aluminium pressure die-casting, CrN in hot extrusion of Al and FUTUR A and PN + FUTURA coating in hot forging of steel parts. Performance tests were carried out in various industrial plants in Slovenia. The results show that an improvement in tool or die life (cost saving) of up to several 100 % is not the decisive factor. More important for these traditional industri es are better reproducibility of the surface quality of the products, an in crease in the manufacturing reliability in heavy machining, a decrease in m anufacturing interruption (down-time) and finally, the protection of the en vironment. (C) 2001 Elsevier Science BN. All rights reserved.