Proceedings of SerbiaTrib '13

Figure 6. The influence of surface treatment andworking on wear [4]The dies can be ranged from the best to worst asweld overlay coated dies, multilayer dies TOKTEKcoated, single layer AlTiN coated dies, plasmanitrided dies and dies as received. This range is alsovalid for the die polishing life, with the exceptionthat it is equal for TOKTEK and AlTiN coatings.Table 1. Number of polishing and total number of partsobtained with experimented dies [8]1stpolishing2ndpolishing3rdpolishing4thpolishing5thpolishingTotalprod.Asreceiv.OperationNitrided4. CONCLUSIONNumber of Forged PartsAlTiNcoatedTOKTEKWeld overlaycoated1st 2ndforg. forg.1440 3920 4810 4660 8690 83301260 2140 1980 2030 8160 84101320 2110 1860 1750 8240 7830- - 1720 1830- - 17804290 9420 12280132102781025930Tools for hot forging are applied in extremelydifficult conditions: impact and very highmechanical load, variable partial and generalthermical load, friction on the surfaces of tools andmore.With these tools, a special kind of coating oncontact surfaces is regularly applied, in order toextend their working life. There are very differentmethods for modifying the tool surface. The mostcommon are different types of heat treatment,which significantly affects the hardness of thesurface layers.Shown results are related to single-layer andmultilayer coatings. It's hard to make a generalconclusion regarding the most influentialparameters, but it is certain that the surfaceroughness has a significant effect on the adhesioncharacteristics of the coating. Also the surfacehardness to which the coating is applied is veryimportant as is the ability to carry the load inquestion.Coatings based on Cr and WC, and weldingprocedures show the best results. From thestandpoint of economy of the process of forging,welding is the best. The temperature and thepercentage of nitrogen in the nitration are veryimportant for tribological characteristics of contactlayers.The ratio of alloying components of chromium(Cr), molybdenum (Mo), and vanadium to carbonratio (H/C) is highly significant influence on thechange of tribological behavior of tool materialregarding wear resistance.ACKNOWLEDGEMENTThe authors wish to acknowledge the financialsupport from the Ministry of Education and Scienceof the Republic Serbia through the project TR34002.REFERENCES[1] V. Vazquez, T. Altan: New concepts in die design -physical and computer modeling applications,Journal of MPT 98, pp. 212-223, 2000.[2] M. Stefanović, R. Stanković: Importance ofTribological Investigations in the Hot Forging,YUTRIB 1995 Herceg Novi, pp, 181-182, 1995.[3] Barrau, C. Boher, R. Gras, F. Rezai-Aria: Analysisof the friction and wear behaviour of hot work toolsteel for forging, Wear, Vol. 255, pp. 1444–1454,2003.[4] M.Gierzynska-Dolna: Effect of the Surface Layer inIncreasing the Life of Tools for Plastic Working:Journal of MWT 6, pp. 193-204, 1982.[5] J. H. Beynon: Tribology of hot metal forming,Tribology International 31, pp. 73–77, 1998.[6] B. Navinsek, P. Panjan, F. Gorenjak: Improvementof hot forging manufacturing with PVD andDUPLEX coatings, Surf. Coat. Technol. 137,pp. 255–264, 2001.[7] M. Bayramoglua, H. Polat, N. Geren: Cost andperformance evaluation of different surface treateddies for hot forging process, Journal of MPT 205,pp. 394–403, 2008.264 13 th International Conference on Tribology – Serbiatrib’13