Abstract
Surface modification engineering is used in many industries to improve specific desired properties. This study aimed to develop a new multi-component material as a protective coating, which would enhance the surface strength and wear resistance of the tool steels. The nanocomposite CrAlSiN coatings with Si contents from 0 at.% to 13.0 at.% were deposited by RF magnetron sputtering. In the ball-on-disc wear tests at room temperature, the improved friction coefficient of (Cr0.5Al0.5)1−xSixN coatings with increasing Si content was revealed. The H3/E*2 ratio of (Cr0.5Al0.5)1−xSixN coatings was found be proportional to the abrasion resistance of coatings, and therefore the (Cr0.5Al0.5)1−xSixN coating with maximum H3/E*2 ratio as high as 0.475 by adding 9.0 at.% Si exhibited superior resistance to plastic deformation and wear. In addition, it was revealed that the columnar grains of the CrAlN coatings were switched to refined and equi-axial ones after Si addition. From the observation of crack propagation, it was evidenced that the equi-axial grains with sophisticated boundary of (Cr0.5Al0.5)1−xSixN coating prevents the direct penetration of the cracks. In the wear tests at high temperature (500 °C, 850 °C and 950 °C), the increased friction coefficient of (Cr0.5Al0.5)1−xSixN coatings with increasing Si content at high temperature was revealed, owing to the occurrence of tribochemical reaction which was verified through XPS analysis. (Cr0.5Al0.5)1−xSixN coating with maximum yield pressure as high as 8336 nm2-GPa by adding 9.0 at.% Si exhibited superior resistance to plastic deformation and wear at high temperature (500 °C, 850 °C and 950 °C). 950 °C). Moreover, the formation of protective third-layer on the surface resulted in the extremely low wear rate at 850 °C and 950 °C. On the basis of these improved tribological behaviors, the superior durability of (Cr0.5Al0.5)1−xSixN coating under extreme environment is thus demonstrated. The duplex coating system is applied to solve the adhesion problem of high residual stress nanocomposite CrAlSiN coating deposited on the AISI 304 substrate. Nitriding experiments are carried out at low temperature 500 oC for 1 hr, 2 hr, and 5 hr with RF power 150 W, 225 W, and 300 W. It is revealed that the substrate with 19.7 at.% nitrogen exhibits the outstanding adhesion strength. The specimen is characterized by X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The strengthen mechanisms in adherence are addressed and can be corresponded to the crystal structure, thermal expansion coefficient, surface roughness, and diffusion layer between the coating and the substrate.