This paper reports on an investigation of the wear of very thin (20–50 nm) Cr2O3 hard coatings, deposited on the linear tape open (LTO) data tape heads. The differential wear of the magnetic poles on the head and subsequent pole tip recession (PTR) leading to an increase in magnetic spacing is the major factor limiting the performance of high data density data tape heads. In order to reduce or eliminate PTR, very thin Cr2O3 hard coatings were employed to reduce PTR. The coatings were deposited on the LTO heads surface using unbalanced magnetron sputtering deposition techniques. Atomic force microscopy was used to analyze the surface topography of the coated head surface. Wear measurement was carried out by the means X-ray photoelectron spectroscopy and Auger electron spectroscopy combined with argon ion depth profiling. By these means, the very small reduction in coating thickness during the wear and hence the wear rate could be accurately determined. Wear tests were conducted in modified HP LTO Ultrium Generation 1 tape drives, and it is shown that wear rates of below 5.6×10−21m3/N⋅m could be measured. Nano indentation and scratch tests were employed to study the wear of the head materials and coated heads, which indicated that pole materials suffer the greatest wear under the same wear test conditions. The coatings on the pole areas have the lowest anti-abrasive wear resistance. Compared to the uncoated heads, the PTR of LTO heads were significant reduced by Cr2O3 coatings.
The effect of high-temperature processing on laser clad Ni-based coatings is studied. Annealing at 1025°C forms thermally stable framework structures with large chromium carbides and borides. As a result, improved hardness and wear resistance of the coating are maintained when heated to 1000°C. Stabilizing annealing also increases the frictional thermal resistance of the NiCrBSi coating. Under high-speed (3.1-9.3 m / s) sliding friction, when the surface layer temperature reaches about 500 -1000°С and higher, the wear resistance of the coating increases by 1.7 -3.0 times. The proposed approach to the formation of heat-resistant coatings is promising, in particular, for a hot deformation tool and other components of metallurgical equipment operating under high thermal and mechanical loads. Such products include crystallizer walls of continuous casting machines. For the walls, the development of laser cladding technology for wear-resistant composite coatings on copper alloys is relevant as an alternative to thermal spraying. The cladding of composite NiBSi-WC coatings of 0.6 and 1.6 mm thickness on a Cu-Cr-Zr bronze substrate heated to 200 -250°C with a diode laser is considered. The presence of boron causes the formation of the W(C, B) carboboride phase, whose hardness is higher than that of WC in the initial powder. Depending on the thickness of coatings and, accordingly, on the duration of heating and the subsequent cooling, the process of secondary carboborides precipitation from the solid solution can be suppressed (in the "thin" coating) or activated (in the "thick" coating). This leads to a higher wear resistance under friction sliding 1.6 mm thickness coating.
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