An evaluation of the effects of the N2/Ar gas flux ratio on various characteristics of TiC0.3N0.7 nano-structure coatings on the cold work tool steel by pulsed DC-PACVD

Abstract

As the radius of argon ions is larger than other fragments in the medium of plasma in the plasma assisted chemical vapor deposition (PACVD) technique, it affects the microstructure and mechanical properties of the coatings. Thus, in this paper, the influence of various N2/Ar gas flow ratios on characteristics of TiCN thin coatings on a cold work tool steel have been investigated. These coatings were produced by the method of pulsed DC-PACVD at a temperature of 480 °C. Field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were employed for determining the microstructure and chemical composition of various coatings. Various mechanical properties such as micro-hardness, nano-hardness, wear behavior, and toughness were also investigated. The obtained results indicated that the N2/Ar gas flow ratio of 0.6 led to optimal mechanical properties. Such ratio reduced the value of the friction coefficient to 0.15 owing to lower roughness. Besides, the growth rate was found to be highest corresponding to a gas flow ratio of 0.5. It was found that the titanium content in such coatings could enhance the growth rate of TiCN coatings. XRD results also demonstrated that the N2/Ar gas flow ratio value of 0.4 resulted in the formation of the TiN and TiC plus the free carbon phases instead of forming the TiC0.3N0.7 phase. The N2/Ar gas flow ratio value of 0.7 also lowered mechanical properties such as the toughness and the micro-hardness. Their values were found to be 2.3 MPam0.5 and 940 HV0.01, respectively.