The influence of residual thermal stresses on the mechanical properties of multilayer α-Al2O3/TiCxN1−x coatings on WC/Co cutting tools

Evaluation of the effect of boride layer structure on the high temperature wear behavior of borided steels

“…16 (as also described in the Appendix), thermal stress developed in boride layers of 31CrMoV9 and X40CrMoV5-1 steels were calculated as þ375 MPa (tensile) and À 505 MPa (compressive), respectively. Since tensile type thermal stress encourages crack initiation and propagation [6], it accelerated material removal from the contact region of the borided 31CrMoV9 steel by crack induced spalling as reflected in the friction curve by heavy fluctuations (Fig. 3).…”

“…If the thermal expansion coefficient of the substrate is larger than that of the surface layer, it expands more than the surface layer during heating and therefore leads to generation of tensile type thermal stress at elevated temperatures. When tensile thermal stress exceeds surface layer strength, vertical channel cracks form on the surface [6]. Unlike tensile thermal stress, compressive thermal stress is beneficial in retardation of crack initiation and/or propagation at surface layer [3,7].…”

“…Unlike tensile thermal stress, compressive thermal stress is beneficial in retardation of crack initiation and/or propagation at surface layer [3,7]. In this respect, a number of scientific investigations have been made to control the thermal stress by altering the structure of the surface layers (multilayered, gradient and composite nature) formed by deposition techniques [4][5][6][8][9][10][11][12][13]. When thermochemical diffusion processes are of concern, boriding results in the formation of single (Fe 2 B) or dual-phase (Fe 2 BþFeB) surface layers on ferrous alloys depending on the process parameters [14,15].…”

In Situ Investigations on Stress and Microstructure Evolution in Polycrystalline Ti(C,N)/α-Al2O3 CVD Coatings under Thermal Cycling Loads

“…A similar discrepancy is observed in α-Al 2 O 3 for both measurements at RT (+1000MPa vs. +500MPa) and 800 • C (+250MPa vs. −400MPa). This difference between experimental and theoretical stresses is understood by the formation of cooling cracks during the cooling step of the CVD process (see Figure 1), and has been discussed previously considering the variation of CTE for the coating/substrate [4,[9][10][11], the density of cracks [4,[9][10][11], the widening of cracks [11,38] or even the formation of subcracks during the temperature steps [10][11][12]. One remaining observation is the appearance of certain deviation from the expected linear behavior of the stress evolution at temperatures between 400 and 600 • C. This kink of stresses has been discussed with regard to the formation of additional cracks [8] or a phase transformation of the cobalt binder phase [11,12].…”

Modeling the composite hardness of multilayer coated systems

“…Due to their outstanding properties and therefore, to the exceptional capabilities provided to the coated system, multilayer coatings have attracted a great deal of attention and in the past few years have become an important research objective. Thus, a wide range of scientific and technological aspects concerning these coatings have been investigated, which include, among others, the correlation between microstructure, mechanical properties (hardness and elastic modulus), impact resistance and tribological performance of different systems [1][2][3][4][5][6][7][8][9][10], deformation mechanisms induced by indentation and nanoindentation damage [11][12][13], effect of layer architecture (number of layers, layer thickness, modulation ratio, bi-layer and multi-layer period) on mechanical properties, tribological performance and oxidation resistance [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], extraction of mechanical properties by different methods [29,30], effect of substrate temperature on residual stresses, hardness and resistivity [31,32] and plastic deformation and size effects [33,34].…”