Development of a Wöhler-like approach to quantify the Ti(CxNy) coatings durability under oscillating sliding conditions

Abstract

The selection of a proper material for the particular engineering application is a complex problem, as different materials offer unique properties and it is not possible to gather all useful characteristics in a single one. Hence, employment of different surface treatment processes is a widely used alternative solution. In many industrial applications, coating failure may be conducive to catastrophic consequences. Thus, to prevent the component damage it is essential to establish the coating endurance and indicate the safe running time of coated system. To this study PVD TiC, TiN and TiCN hard coatings have been selected and tested against polycrystalline alumina smooth ball. The series of fretting tests with reciprocating sliding at the frequency 5Hz have been carried out under 50-150N normal loads and under wide rage of constant as well as variable displacement amplitudes from 50µm to 200µm at a constant value of relative humidity of 50% at 296K temperature. To quantify the loss of material a dissipated energy approach has been applied where the wear depth evolution is referred to the cumulative density of friction work dissipated during the test. Different dominant damage mechanisms have been indicated for the investigated hard coatings, which is debris formation and ejection in case of TiC coating and progressive wear accelerated by cracking phenomena in case of TiN and TiCN coatings. Energy-Wöhler wear chart has been introduced, in which the critical 1 dissipated energy density corresponds to the moment when the substrate is reached after a given number of fretting cycles. Two different methods to determine the critical dissipated energy density are introduced and compared. The Energy-Wöhler approach has been employed not only to compare the global endurance of the investigated systems but also to compare the intrinsic wear properties of the coatings. It has been shown that the fretting wear process is accelerated by the stress-controlled spalling phenomenon below a critical residual thickness and a severe decohesion mechanism is activated. Finally the applicability of the investigated method to other coated systems subjected to wear under sliding conditions is discussed and analyzed. The perspectives of this new approach are elucidated.

Influencia de las nanopartículas de Ag sobre las propiedades mecánicas y tribológicas y en el efecto citotóxico y bactericida de los recubrimientos de TaN(Ag)

“…Una vez en la cámara de pulverización, las muestras se sometieron a una limpieza iónica con argón durante 30 min. Previo a la deposición del sistema de recubrimientos TaN(Ag), los sustratos de acero fueron endurecidos superficialmente mediante un proceso de nitruración por plasma pulsado, utilizando una atmosfera de argón/nitrógeno/ hidrógeno, a una presión de 6,3x10 -1 mbar, un voltaje bias de -750 V y a una temperatura de 380 °C durante 9 h. Posteriormente y con el fin de reducir la tensiones residuales en la interfase del acero inoxidable AISI 316L y el recubrimiento por la diferencia de dureza (Liskiewicz et al, 2005), se depositó una monocapa de anclaje de tantalio de aproximadamente 70 nm; una vez formada la capa de anclaje se procedió con el ingreso de nitrógeno para contribuir a la formación del nitruro de tantalio. Los recubrimientos de TaN(Ag) se realizaron según las condiciones descritas en la Tabla 1, en la cual se incluyen los espesores alcanzados para cada uno.…”

Gross slip fretting wear performance of a layered thin W-DLC coating: Damage mechanisms and life modelling

“…A similar approach has been presented based on the energy wear approach in [38,42,43] to quantify fretting contact durability of a coating. A contact wear endurance curve was presented, in which the global endurance (number of cycles to substrate exposure) of the coated systems investigated could be assessed from its mean contact energy density.…”

Structure and mechanical properties of low temperature magnetron sputtered nanocrystalline (nc-)Ti(N,C)/amorphous diamond like carbon (a-C:H) coatings

“…The TiN layer can also beneficially act as a diffusion barrier between the TiCN layer and the substrate at elevated temperatures [12]. An approach to demonstrate the amount of energy dissipated under oscillating loaded sliding contact conditions using classical Wohler fatigue fretting curves showed that the amount of dissipated energy is significantly reduced after a large number of cycles for single layer TiN and TiCN coatings, due to cracking phenomena [15]. Therefore multilayer TiN/TiCN with additional top layers of TiC or a-C:H coatings can dissipate greater energy resulting in gradual debris formation and coating ejection at higher wear cycles thus prolonging coating durability [15].…”

“…An approach to demonstrate the amount of energy dissipated under oscillating loaded sliding contact conditions using classical Wohler fatigue fretting curves showed that the amount of dissipated energy is significantly reduced after a large number of cycles for single layer TiN and TiCN coatings, due to cracking phenomena [15]. Therefore multilayer TiN/TiCN with additional top layers of TiC or a-C:H coatings can dissipate greater energy resulting in gradual debris formation and coating ejection at higher wear cycles thus prolonging coating durability [15]. It should be noted that the evaluation of the endurance of coatings through the classical Wohler-curves approach is a concept developed not as a function of maximum applied pressure but as a function of friction [14].…”