Adhesion failures on hard coatings induced by interface anomalies

Abstract

a b s t r a c tIn this work, the lack of adhesion occurred during the up-scaling of the deposition of tribological coatings in a semi-industrial apparatus is interpreted. The adhesion problems were detected for both hard and self-lubricant coatings from W-Ti-N and W:C systems, respectively, when they were deposited in a 4 cathodes TEER Ò chamber by reactive unbalanced magnetron sputtering. In spite of cleaning the substrates surface by ion bombardment prior to deposition, by establishing a discharge close to the substrate, insufficient adhesion critical load values were measured by scratch-testing. A powerful set of complementary techniques was used to the detailed analysis of the interfaces in order to understand and overcome the adhesion problems: RBS gave some insights on the nature of the problem by detecting composition anomalies in the substrate/coating interface; Auger spectroscopy was used for identifying the underneath chemical composition close to the interface; cross section TEM gave the final evidence of the presence of a contamination layer attributed to malfunctioning of the ion cleaning process, which was the cause of the lack of adhesion.

Argon plasma treatment techniques on steel and effects on diamond-like carbon structure and delamination

“…As the bias voltage is increased from 450V to 600V bias the formation of a nano-structured interface with between the film and substrate further enhances the film-substrate adhesion. Unlike the spallations in films treated with Ar plasma at 300 -450V bias, the very occasional breaches in the 600 V treated film appear to be unlinked to the crack lines, as shown in figure 3 d, and are perhaps related to isolated substrate anomalies or contamination, which have been previously shown to be responsible for lower film adhesion [13]. Figure 4 shows scanning electron microscopy images of the surfaces of diamond-like carbon films deposited on substrates with treatments at 300V, 450V and 600V.…”

“…Many groups producing amorphous carbon or amorphous hydrogenated carbon films use thin interlayers with incorporation of elements such as titanium [13], tungsten [14][15][16] or silicon [6,7,10,[17][18][19]. These layered structures have improved adhesion on substrates including stainless and high-speed steels [6,7,19] silicon [7,17] and Ti-Al-V alloys [18].…”

“…Other research teams have used thick interlayers such as ceramic or epoxy [5]. Many groups [5,6,13,[19][20][21][22] also utilise an argon plasma pretreatment process, and this has been shown to be important in film adhesion [5,20,21]. However, parameters for this process vary substantially between groups; duration can vary from 5min to 1 hr and bias voltage from 300V to 700V.…”

Substrate and material transfer effects on the surface chemistry and texture of diamond‐like carbon deposited by plasma‐enhanced chemical vapour deposition

“…However, high internal stresses within the applied film can limit useful DLC coating thickness to less than 10 mm, thus limiting practical application in some areas. To improve substrate-film adherence, many groups have used thin interlayers, incorporating materials such as titanium, [8] tungsten [9] or silicon. [2,5,10,11] An alternative strategy has been developed, [7] which uses a thick epoxy layer with a DLC surface thin film, with applications for aircraft landing gear.…”

Carbon-based coatings doped by copper: Tribological and mechanical behavior in olive oil lubrication

“…inertness, optical transparency, or thermal conductivity [1,2,3,4] . The addition of metallic or non-metallic elements can improve the coating tribological properties [5,6] and the adhesion, which can be related to a minimization of the residual stresses [7,8,9] .…”