Comparative Investigation of the Mechanical and Wear Properties of Multilayer Si-DLC/DLC Films

Abstract

In this study, multilayer diamond-like carbon fi lms 1µm thick with di ff erent numbers of multilayer repetitions were deposited onto austenitic stainless steel SUS304 substrates using di ff erent source gases. The in fl uence of the gas and the di ff erence in the number of multilayer repetitions on the adhesion strength and wear resistance of the fi lms was subsequently investigated. The samples were subjected to cross- sectional microstructure observations, elemental analysis by glow-discharge optical emission spectroscopy, nano-indentation tests, Rockwell indentation tests, friction and wear tests, and delamination tests. The nano-indentation tests showed that the fi lms prepared using C 2 H 2 gas were harder than those prepared using CH 4 gas. In addition, irrespective of the gas used, the fi lm hardness was improved when four layers rather than two layers were deposited. However, the hardness of the eight layers fi lm decreased. The Rockwell indentation tests showed no improvement in adhesiveness when the gas or the number of multilayer repetitions was varied. The wear tests revealed that the friction coe ffi cient of the fi lms prepared using C 2 H 2 gas was smaller than that of fi lms prepared using CH 4 gas. No di ff erence was observed with increasing number of multilayer repetitions. The delamination tests showed that the distance until delamination of the fi lms prepared using C 2 H 2 gas was longer than that of the fi lms prepared using CH 4 gas. In addition, the distance until delamination was improved by changing the number of multilayer repetitions from two layers to four layers for both gases but decreased when the number of repetitions was extended to eight layers. In this study, the value of H / E (hardness / Young ’ s modulus) increased and various characteristics improved with increasing number of multilayer repetitions. [doi:10.2320 matertrans.MT-M2020261]