Structure, mechanical properties and oxidation resistance of iso and non-iso architected TiN/Cr multilayers coatings deposited by magnetron sputtering

Abstract Iso and non-iso architected TiN/Cr multilayers with constant composition were deposited by balanced magnetron sputtering aiming to investigate the influence of different architectures over coatings structures and properties. Glow discharge optical emission spectroscopy analyses were used to determine in-depth constituents and suggested that no diffusion of elements occurred between layers in room temperature. Field emission gun scanning electron microscopy analyses showed that all multilayers presented sharp interfaces and low porosity microstructures, with column-like grain growth influenced by layer sizes. Glancing angle X-ray diffraction analyses showed that multilayers consist of polycrystalline α-Cr and δ-TiN phases with a main peak in Cr(110) plane. The overlapping of TiN onto metallic layers led to the suppression of growth in the TiN(111) plane, although TiN layers thicker than 50 nm demonstrated a growth in plane TiN(200). Nanoindentation tests registered equal hardness values for all multilayers of around 16.2 GPa, on the other hand, a tendency to improve hardness has been identified for hierarchical multilayer. Oxidation tests revealed that architectures with thicker TiN top layers presented an improved oxidation resistance up to 600 ºC, probably due to growth in more compact TiN(200) plane. However, TiN/Cr coatings did not resist integrally to oxidation tests at 750 ºC.

本研究采用平衡磁控溅射法制备了成分恒定的等结构与非等结构TiN/Cr多层膜，旨在探究不同结构设计对涂层组织与性能的影响。通过辉光放电光发射光谱（Glow Discharge Optical Emission Spectroscopy）分析表征了涂层深度方向的成分分布，结果表明室温下各层间未发生元素互扩散。场发射枪扫描电子显微镜（Field Emission Gun Scanning Electron Microscopy）分析显示，所有多层膜均具有清晰的界面与低孔隙率微观组织，柱状晶粒生长行为受层厚调控。掠入射X射线衍射（Glancing Angle X-ray Diffraction）分析表明，多层膜由多晶α-Cr相与δ-TiN相组成，其中Cr相的特征衍射峰以Cr(110)晶面为主要衍射峰。金属层上的TiN沉积生长抑制了TiN(111)晶面的生长，而当TiN层厚超过50 nm时，会出现TiN(200)晶面的择优生长。纳米压痕测试结果显示，所有多层膜的硬度均约为16.2 GPa，数值相近；而分级结构多层膜则表现出硬度提升的趋势。氧化测试结果表明，顶层TiN厚度更大的多层膜在600 ℃以下具有更优异的抗氧化性能，这可能源于其更致密的TiN(200)晶面生长结构。但在750 ℃的氧化测试中，TiN/Cr涂层无法保持结构完整性。