{"title":"Effect of post-annealing on the thermal stability and residual stresses in CVD (Al,Ti)N coatings investigated by in situ synchrotron diffraction","authors":"","doi":"10.1016/j.ijrmhm.2024.106810","DOIUrl":null,"url":null,"abstract":"<div><p>The stress in thin wear resistant coatings is of great importance for the performance and service life of tools for metal cutting. In this work we have performed detailed investigations of the phase stability and temperature-dependent residual stresses in Al-rich Al<sub>x</sub>Ti<sub>1-x</sub>N ((Al,Ti)N) coatings deposited by chemical vapor deposition (CVD) on cemented carbide substrates. One as-deposited (Al,Ti)N coating and one coating post-annealed at 850 °C for 3 h were heated to 1200 °C while the structure and residual stresses were monitored by <em>in situ</em> high energy synchrotron X-ray diffraction. In the as-deposited state, the coating is in tensile stress at room temperature, but post-annealing resulted in a reduction of the room temperature residual stress. This lowering can be explained by growth of hexagonal AlN (hAlN) at the (Al,Ti)N grain boundaries during the isothermal hold time. Upon heating, the temperature-dependence of the residual stresses in both coatings are initially controlled by the mismatch in coefficients of thermal expansion (CTE) with the substrate, which leads to compressive stresses at typical service temperatures. Decomposition starts gradually at around 850–900 °C, resulting in an accelerated development of large compressive stresses with increasing temperatures, until the entire coating is transformed at temperatures just below 1100 °C. The growth of hAlN initiates slightly higher in temperature after post-annealing, whereas the upper limit for complete transformation remains unaffected. The lowered room temperature tensile stress after post-annealing leads to higher compressive stress at service temperatures, which is expected to improve the performance and service time of the coated tool.</p></div>","PeriodicalId":14216,"journal":{"name":"International Journal of Refractory Metals & Hard Materials","volume":null,"pages":null},"PeriodicalIF":4.2000,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0263436824002580/pdfft?md5=296a87e26ad12e85a7bad4d69c19fe8f&pid=1-s2.0-S0263436824002580-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Refractory Metals & Hard Materials","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0263436824002580","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The stress in thin wear resistant coatings is of great importance for the performance and service life of tools for metal cutting. In this work we have performed detailed investigations of the phase stability and temperature-dependent residual stresses in Al-rich AlxTi1-xN ((Al,Ti)N) coatings deposited by chemical vapor deposition (CVD) on cemented carbide substrates. One as-deposited (Al,Ti)N coating and one coating post-annealed at 850 °C for 3 h were heated to 1200 °C while the structure and residual stresses were monitored by in situ high energy synchrotron X-ray diffraction. In the as-deposited state, the coating is in tensile stress at room temperature, but post-annealing resulted in a reduction of the room temperature residual stress. This lowering can be explained by growth of hexagonal AlN (hAlN) at the (Al,Ti)N grain boundaries during the isothermal hold time. Upon heating, the temperature-dependence of the residual stresses in both coatings are initially controlled by the mismatch in coefficients of thermal expansion (CTE) with the substrate, which leads to compressive stresses at typical service temperatures. Decomposition starts gradually at around 850–900 °C, resulting in an accelerated development of large compressive stresses with increasing temperatures, until the entire coating is transformed at temperatures just below 1100 °C. The growth of hAlN initiates slightly higher in temperature after post-annealing, whereas the upper limit for complete transformation remains unaffected. The lowered room temperature tensile stress after post-annealing leads to higher compressive stress at service temperatures, which is expected to improve the performance and service time of the coated tool.
期刊介绍:
The International Journal of Refractory Metals and Hard Materials (IJRMHM) publishes original research articles concerned with all aspects of refractory metals and hard materials. Refractory metals are defined as metals with melting points higher than 1800 °C. These are tungsten, molybdenum, chromium, tantalum, niobium, hafnium, and rhenium, as well as many compounds and alloys based thereupon. Hard materials that are included in the scope of this journal are defined as materials with hardness values higher than 1000 kg/mm2, primarily intended for applications as manufacturing tools or wear resistant components in mechanical systems. Thus they encompass carbides, nitrides and borides of metals, and related compounds. A special focus of this journal is put on the family of hardmetals, which is also known as cemented tungsten carbide, and cermets which are based on titanium carbide and carbonitrides with or without a metal binder. Ceramics and superhard materials including diamond and cubic boron nitride may also be accepted provided the subject material is presented as hard materials as defined above.