Effect of Interlayer Thickness on Nano-Multilayer Coating Performance during High Speed Dry Milling of H13 Tool Steel

Abstract

The TiAlCrSiYN-based family of physical vapor deposition (PVD) coatings were systematically designed through the incorporation of TiAlCrN interlayer to increase coating adhesion and consequently the tool life for extreme conditions that arise during dry high-speed milling of hardened tool steels. The investigation in the present paper intends to explain the effect of TiAlCrN interlayer thickness on the overall coating properties and cutting performance. A comprehensive characterization of the structure and properties of the coatings has been performed using focused ion beam (FIB), scanning electron microscope (SEM), X-ray powder diffraction (XRD), nanoindentation, ramped load scratch test, repetitive load wear test, and nano-impact test. The wear test at a subcritical load of 1.5 N showed that there was a gradual improvement in coating adhesion to the substrate as the interlayer thickness increased from 100 to 500 nm. However, the wear performance, being related to the ability of the coating layer to exhibit minimal surface damage under operation, was found to be associated with micro-mechanical characteristics (such as hardness, elastic modulus). Around a 40% increase in the cutting performance with 300 nm interlayer exhibited that a substantial increase in tool life can be achieved through interlayer thickness variation, by obtaining a balance between mechanical and tribological properties of the studied coatings.

Characteristics and Wear Mechanisms of TiAlN-Based Coatings for Machining Applications: A Comprehensive Review

“…These cracks can be seen in Figure 40. The employment of TiAlCrSiYN/TiAlCrN has also seen some studies lately, with Chowdhury et al [113,114] evaluating the mechanical properties of this coating for various coating architectures and differing interlayer thicknesses. The authors also employ these coatings in the dry milling of stainless steel at a machining speed of 600 m/min.…”

“…As seen in previous studies, the thinner the interlayer thickness is, the higher the hardness is. Chowdhury et al [113,114] also compare these multilayered coatings with monolithic TiAlCrSiYN and TiAlCrN coatings. It was concluded that the nanolayered coatings, with optimized interlayer thickness produced the best results in terms of cutting performance and wear behavior, indicating that these types of nanolayered coatings are an excellent choice for extreme machining applications.…”

“…The mechanical properties from the coatings that were mentioned in the previous subsubsection are going to be presented in Table 5. [115] 33.0-39.0 550-570 TiAlN/CrAlN [112] 25.0-30.0 N/A TiAlCriSiYN/TiAlCiN [113,114] 24.0-33.0…”

“…Another element that as seen some research is Si, as the use of this element is quite popular in machining applications, especially for the TiAlSiN coating, which exhibit better mechanical properties and wear behavior than the TiAlN coating [65]. Its employment is quite beneficial, being used in some monolayered coatings, such as the CrTiAlSiN [71], and in some multilayered architectures [94], and nanolayered coatings [106,107,113,114]. As seen from the studies presented above [123][124][125] the TiAlSiCN coating has a very high thermal stability and excellent mechanical properties.…”

“…It was noticed that there are many research papers about milling operations using the TiAlN-based coated tools. However, for both machining cases, it was found that there is a large interest in the study of the wear performance of these coatings in the cutting of steels [70,71,74,81,83,97,98,100,[111][112][113][114]117], titanium alloys [72,75,76,82,96,115,116] and Inconel [73,[78][79][80]99]. This is due to these alloys being employed in the aeronautical industry, making the study of the machinability of these materials quite interesting.…”