Investigation of Multiparameter Laser Stripping of AlTiN and DLC C Coatings

The lifetime and properties of cutting tools and forming moulds can be prolonged and enhanced by the deposition of hard, thin coatings. After a certain period of usage, the coating will deteriorate. Any remaining coating must be removed prior to successful recoating. Laser stripping is a fast and environmentally friendly coating removal method. In this paper, we present laser removal of two types of coatings deposited on a 1.2379 tool steel substrate, namely, an AlTiN coating with high hardness and a DLC C coating with a small coefficient of friction (COF). A powerful nanosecond laser was employed to remove the coating from the substrate with high efficiency, along with suitable residual surface roughness. Measurements were taken of surface roughness, removed depth, and working time on a stripped area of 1 cm2. The samples were evaluated under a microscope, with a 3D profilometer, and by EDS chemical analysis. Successful removal of the coating was confirmed by optical analysis, but detailed chemical characterisation showed that about 30% of the coating element may remain on the surface. Moreover, a working time of less than 7.5 s per cm2 was obtained in this study. In addition, it was shown that the application of a second low energy, high frequency laser beam pass leads to remelting of the peaks of the material and reduced surface roughness.

Influence of the microstructure of tool coatings based on Ti and Al on the blunting process during chipboard processing

Influence of the microstructure of tool coatings based on Ti and Al on the blunting process during chipboard processing.This work concerns three different tool coatings containing Ti and Al. i.e. TiN, AlTiN, TiAlSiN applied to cutting tools used in the machining of wood materials. In the case of the AlTiN coating, a multilayer structure with alternately arranged AlTiN and TiN nano-layers was used. The above coatings were applied to standard replaceable knives used for CNC milling heads made of WC-Co cemented carbide. The deposition process was carried out using the RF Magnetron Sputtering method. During the measurement on a workshop microscope, the VBmax index measured on the clearance face was adopted as the wear criterion. The research proved a very good behaviour of the TiN/AlTiN multilayer coating, for which the longest average service life which was recorded exceeded the results obtained for the reference tool by about 30%. The addition of silicon, which was supposed to increase the abrasion resistance, only did not improve the durability of the blade, it actually worsened it by 6%. In addition, the coating, which has been widely used in the machine industry for a very long time, i.e. TiN, did not extend the tool life significantly (+ 7%).

Investigations of Damping Capacity and Fretting Wear Behaviour of AlTiN Coated Friction Damper

The concept of friction damper is widespread technique and used to reduce the structural vibrations in many industrial applications. These friction dampers are generally coated with low wear rate materials to reduce the fretting wear. This paper investigates the use of physical vapor deposition (PVD) nitride based AlTiN coating material applied over the stainless steel friction damper to enhance the damping capacity and to reduce the fretting wear. A friction test rig has been developed to measure the dynamic hysteresis characteristics of friction damper at high temperature (700 °C). The damping capacity and fretting wear analysis is carried out at room temperature, 300 °C and 600 °C. The force versus displacment characterisitcs curve is used to predict the damping capacity and fretting wear analysis is carried out at microscopic level for the comparision. It is observed that at room temperature AlTiN coated friction damper has not much influence to improve the damping capacity and to reduce the fretting-wear. However, at high temperature it has better damping capacity and less wear in comparision to uncoated friction damper. Wear behaviour in coated and uncoated damper is different at room temperature and at elevated temperature.