Electron beam assisted physical vapor deposition of very hard TiCN coating with nanoscale characters

摘要

The work concerns electron beam assisted physical vapor deposition (EB-PVD) of titanium carbo-nitride (TiCN) on D2 tool steel. First, D2 steel substrate was heat treated to support and improve the load bearing capacity of the coating. To reduce the intrinsic gap between D2 substrate and TiCN coating and to improve the adhesive strength of the coating, a thin bond coat of Ti was EB-PV deposited on D2 steel prior to TiCN coating. The deposited coating was characterized in depth using XRD, SEM, AFM, profilometry and nanoindentation; its performance was assessed by the wear tests. The results demonstrated that EB-PVD process is successful in uniform deposition of nanograined (5.7 nm) TiCN coating; this character of the coating enhances its mechanical responses and cohesive strength. AFM topographic characterization confirms nanoscale smoothness of the TiCN coating which is a key factor in upgrading the wear resistance and tribological behavior of the coating. Nanoindentation results showed that the deposited coating is very hard; it is also tough enough. The hardness of the TiCN in this work is too much higher than those reported in the literature by similar works. AFM and nanoindentation results showed that a TiCN coating with thickness of 1.6 mu m and roughness of 22 nm exhibits a hardness of 3552 HV which is much higher than those hardnesses reported in previous works. The wear tests showed that the deposited TiCN coating has a higher wear resistance than the D2 steel as well as TiN coating; this better performance is attributed to the modifications made in the coating process and its nanoscale characters.