Mechanical and Tribological Properties Evolution of [Si3N4/Al2O3]n Multilayer Coatings

Abstract

Multilayer coatings [Si3N4/Al2O3]n have generated great interest due to their intriguing properties which have made them a potential candidate to be implemented in different processes within the food and pharmaceutical industries. Unfortunately, this multilayer system based on [Si3N4/Al2O3]n does not have strong tribological studies that could express in an emphatic way its own tribological characteristics. For this reason, the aim of this research consisted of a detailed study of the evolution of the mechanical and tribological properties of the [Si3N4/Al2O3]n coatings as a function of the bilayer number n=1, 10, 30 and 70, with special emphasis on the tribological analysis in a dry and lubricated environment. It was determined that the mechanical properties such as the hardness and the elastic modulus increased by 29% and 6.3%, while the friction coefficient in a dry and lubricated environment decreased by 33% and 81.8%, respectively, when increasing the bilayers from n=1 to n=70. Thus, the present study determined that the coating [Si3N4/Al2O3]70 presented ideal properties that make it a promising candidate to be implemented as a protective coating on processing devices within the food and pharmaceutical industry.

Analysis of the Tribological Evolution of Nitride-Based Coatings

“…In addition, the identification of cohesive failure (Lc1) and adhesive failure (Lc2) was performed using the NANOVEA SCRATCH TESTER software, which analyzes the change of the friction coefficient versus load or distance, and the results were corroborated by optical micrographs and SEM micrographs of the scratch tracks. The coatings thickness and the wear scratch images were obtained by using a KLA Tencor D-120 profilometer; the thickness of all the coatings was 3 μm [6,9].…”

“…A specific type of coatings such as those based on nitrides, which have generated great interest within various and novel coating systems, these coatings were implemented approximately since 1970 [4], being one of the first anti-wear coatings used in the industry. This type of coatings have great hardness, high resistance to wear and high resistance to Tribology corrosion among other interesting properties, such as TiN [4], TiCrN [5], [Al 2 O 3 / Si 3 N 4 ] [6], TiCN [7], BCN [8] among other configurations.…”

Al2O3-TiO2 coatings deposition by intermixed and double injection SPS concepts

“…Such multi-material coatings can be obtained in different ways, i.e., by: (i) incorporation of agglomerated or sintered powders, where one powder particle has a complex chemical composition [23], (ii) simultaneous deposition of two separate feedstocks [24], (iii) spraying of layered microstructures [25], (iv) building of a gradient structure, where one material passes gradually into another one, and (v) incorporation of fine nano platelets, which are employed as the reinforcement of monolithic coating [11]. Currently, the main approach is the so-called hybrid spraying.…”