The effect of (Ti+Al):V ratio on the structure and oxidation behaviour of TiAlN/VN nano-scale multilayer coatings

Abstract

Nano-scaled multilayered TiAlN/VN coatings have been grown on stainless steel and M2 high speed steel substrates at U B =-85 V in an industrial, four target, Hauzer HTC 1000 coater using combined cathodic steered arc etching/unbalanced magnetron sputtering. X-ray diffraction (XRD) has been used to investigate the effects of process parameters (Target Power) on texture evolution (using texture parameter T*), development of residual stress (sin 2  method) and nano-scale multilayer period. The composition of the coating was determined using energy dispersive X-ray analysis. The thermal behaviour of the coatings in air was studied using thermo-gravimetric analysis, XRD and scanning electron microscopy. The bi-layer period varied between 2.8 and 3.1 nm and in all cases a {1 1 0} texture developed with a maximum value T* = 4.9. The residual stress varied between-5.2 and-7.4 GPa. The onset of rapid oxidation occurred between 62 and 645 C depending on the (Ti+Al):V ratio. After oxidation in air at 550 C AlVO4, TiO2 and V2O5 phases were identified by XRD with the AlVO4, TiO2 being the major phases. The formation of AlVO4 appears to disrupt the formation of Al2O3 which imparts oxidation resistance to TiAlN based coatings. Increasing the temperature to 600 and 640 C led to a dramatic increase in the formation of V2O5 which was highly oriented (001) with a plate-like morphology. At 640 C there was no evidence of the coating on XRD. Increasing the temperature to 670C led to further formation of AlVO4 and a dramatic reduction in V2O5.

TEM-EELS study of low-friction superlattice TiAlN/VN coating: the wear mechanisms

“…The TiAlN/VN is a multilayer nitride coating having nanometer-scale TiAlN and VN bi-layers, a NaCl-type cubic structure, and polycrystalline columnar morphology [13,14]. Its outstanding tribological properties, as compared to other hard nitrides in the TiN and TiAlN family, are the combined low dry sliding friction coefficient (= 0.4-0.6) and extremely low wear rate in a scale of 10 -17 m 3 N -1 m -1 [15,16]. This has led to successful applications in cutting tools in dry milling wrought and cast aluminium alloys [17,18].…”

“…Meanwhile, it was found in a series of iso-thermal annealing tests that TiAlN/VN coatings for a range of chemical compositions oxidize at temperatures between 500 and 700 0 C, which is obviously lower than the onset oxidation temperature of TiAlN (700-800 0 C). The oxidation led to the formation of a number of oxides, including V2O5 and other types like AlVO4, TiO2 and Al2TiO5 [15,20,21]. Note that the oxide V2O5 has an orthorhombic layer structure with layers stacking along the c-axis [22,23].…”

“…The week interlayer V-O interaction makes easy the cleavage and shear deformation of the structure and therefore brings in some solid-lubricating property. It was therefore speculated that the V2O5 oxide in the wear product, if adhered on the worn surface, is responsible for the low friction coefficient [15,24]. However, more details of the wear mechanisms of the TiAlN/VN were not clear.…”

Oxidation and diffusion processes during annealing of TiSi(V)N films

“…V 2 O 5 , Ag 2 Mo 2 O 7 ) [6][7][8][9]. Among these elements, particular attention has been given to the vanadium-containing coatings (Magnéli phases V n O 2n−1 ), which showed interesting tribological properties in the temperature range 500-700•C [2,[10][11][12][13][14][15]. Dissimilar series of V-based hard coatings have been developed, such as ternary…”

Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior

“…Systematic optimization of the coating composition was made by addition of various elements (such as Cr, Si, Y, B and others) to TiAlN [24,[63][64][65] and corresponding elements to AlCrN-based coatings [62,[66][67][68]. Various designs of hard coatings have been introduced as well [48,[69][70][71][72][73][74][75][76][77][78][79][80]. Nanomultilayered coatings [3,[81][82][83] consisting of alternating nanolayers [70,[84][85][86][87][88] with varied and modulated chemical compositions have been a promising development that improved the coating characteristics and enhanced their wear performance [81][82][83].…”