Optimization of nitrided case structure in composite layers created by duplex treatment on the basis of PVD coating adhesion measurement

The paper concerns the process of the composite:'nitrided layer-PAPVD coati ng' creation on substrates made of hot working steel. The composite propert ies are determined by the appropriate selection of coating parameters and n itrided case structure. The results of research concerning the influence of a method of substrate nitriding and the created nitrided case structure on the adhesion and plastic properties of the PAPVD coatings are presented in the paper. Substrates made of hot working steel EW X35CrMoV5 (0.4% C, 0.4% Mn, 1.0% Si, 5.0% Cr, 1.3% Mo, 0.3% V) underwent different processes of th ermo-chemical and finishing surface treatment in order to obtain a nitrided layer of a different structure: Fe-alpha(N), Fe-alpha(N)+ 'white layer'-ep silon,gamma'. Research was carried out for nitrided layers created in a con trolled gas nitriding process. Four different coatings of nitrides, TIN, Ti (C,N), CrN, (Ti,Cr)N, were deposited on substrates with nitrided layers usi ng the are-vacuum method and the MZ-383 equipment manufactured by Metaplas Ionon. For composite 'nitrided layer/PAPVD coating' prepared in this way, t he authors carried out a metallographic analysis, using the optical microsc ope Neophot32, and measurements of surface roughness of the deposited nitri des. The X-ray phase analysis carried out on the Philips PW1830 diffractome ter enabled the phase composition of nitrided layers and the phase composit ion and the lattice parameter of the deposited PAPVD coatings to be determi ned. Then, the authors carried out measurements of the coating adhesion for all investigated composites using the scratch-test method by means of Reve test-CSEM. The authors demonstrated the significant influence of the presen ce of titanium ions (Ti+), in the vacuum are deposition process, on the pro perties of the composite nitrided layer/PVD coating. The presence of titani um ions in the technological process deteriorates adhesion of the PVD coati ng to the nitrided substrate, when the nitrided layer includes the compound zone. This effect was not observed for a CrN coating deposited without the participation of titanium ions. (C) 1999 Elsevier Science S.A. All rights reserved.