Publicação
Nitride based semiconductor thin films for high temperature sensors deposited by magnetron sputtering
| Resumo: | In modern manufacturing, real-time temperature monitoring at the cutting tool-workpiece interface is fundamental for optimizing tool performance, predicting wear, and improving productivity in high-precision machining processes. However, the lack of practical temperature sensing solutions capable of operating in the harsh environments typically found in the metal cutting industry, especially during the machining of hard-to-cut materials like titanium alloys, remains a significant challenge in this industry.This dissertation investigates the development and integration of ternary transition metal nitride (TMN) thin-film thermistor sensors, specifically titanium aluminum nitride (TiAlN) and zirconium aluminum nitride (ZrAlN), for high-temperature sensing applications in metal cutting tools. More specifically, explores the thermoresistive properties of materials typical used for tool protection developed by direct current magnetron sputtering (DCMS) in closed-field configuration. Through a combinatorial deposition approach, the Al content in the Ti1-xAlxN and Zr1-xAlxN films was optimized to maintain a face-centered cubic (fcc) structure and negative temperature coefficient (NTC) behavior, with ideal ratios identified at 0.21 ≤ x ≤ 0.56 for TiAlN and x ≤ 0.34 for ZrAlN. X-ray photoelectron spectroscopy (XPS) and electrical impedance spectroscopy (EIS) revealed that electron hopping at grain boundaries governs the conduction mechanisms at lower temperatures, facilitated by free electrons from Ti and Zr.The upscaling of these materials to integrate into the cutting tool showed that both materials demonstrated suitability for high-temperature sensing up to 750°C, with Ti0.47Al0.53N and Zr0.7Al0.3N thin films exhibiting sensitivity (β) around 100 K and 850 K, respectively. However, the ZrAlN demonstrating higher resistivity ≈ 8.0 × 105 µΩcm. Structural analysis indicated that TiAlN exhibits a highly textured fcc structure with a dominant (111) orientation, while ZrAlN presents mixed phases of poorly crystalline cubic ZrN and orthorhombic Zr3N4. Scanning transmission electron microscopy (STEM) revealed the columnar morphology with nanolayers alternating in Al content for both coatings. When integrated into a multilayer architecture – with insulation and wear-resistant layers – for cutting tools, both nitride sensors displayed distinct thermistor behavior, making β curve calibration challenging above 400°C. Nevertheless, during in-situ temperature monitoring of titanium turning, the cutting temperature was found to be predominantly influenced by the cutting speed (Vc) and depth of cut (ap), rather than by the feed rate (f). Additionally, it was found that the utilization of cooling is the most effective method for reducing cutting temperatures and that sensor positioning on the rake face is critical for capturing peak thermal data. |
|---|---|
| Autores principais: | Martins, Bruno da Costa |
| Assunto: | NTC thin-film thermistor Reactive sputtering Temperature sensing Tool condition monitoring Smart tools Medição de temperatura Termístor de filme fino Avaliação da condição da ferramenta Pulverização catódica reativa Ferramentas inteligentes |
| Ano: | 2025 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Universidade de Coimbra |
| Idioma: | inglês |
| Origem: | Estudo Geral - Universidade de Coimbra |
| Resumo: | In modern manufacturing, real-time temperature monitoring at the cutting tool-workpiece interface is fundamental for optimizing tool performance, predicting wear, and improving productivity in high-precision machining processes. However, the lack of practical temperature sensing solutions capable of operating in the harsh environments typically found in the metal cutting industry, especially during the machining of hard-to-cut materials like titanium alloys, remains a significant challenge in this industry.This dissertation investigates the development and integration of ternary transition metal nitride (TMN) thin-film thermistor sensors, specifically titanium aluminum nitride (TiAlN) and zirconium aluminum nitride (ZrAlN), for high-temperature sensing applications in metal cutting tools. More specifically, explores the thermoresistive properties of materials typical used for tool protection developed by direct current magnetron sputtering (DCMS) in closed-field configuration. Through a combinatorial deposition approach, the Al content in the Ti1-xAlxN and Zr1-xAlxN films was optimized to maintain a face-centered cubic (fcc) structure and negative temperature coefficient (NTC) behavior, with ideal ratios identified at 0.21 ≤ x ≤ 0.56 for TiAlN and x ≤ 0.34 for ZrAlN. X-ray photoelectron spectroscopy (XPS) and electrical impedance spectroscopy (EIS) revealed that electron hopping at grain boundaries governs the conduction mechanisms at lower temperatures, facilitated by free electrons from Ti and Zr.The upscaling of these materials to integrate into the cutting tool showed that both materials demonstrated suitability for high-temperature sensing up to 750°C, with Ti0.47Al0.53N and Zr0.7Al0.3N thin films exhibiting sensitivity (β) around 100 K and 850 K, respectively. However, the ZrAlN demonstrating higher resistivity ≈ 8.0 × 105 µΩcm. Structural analysis indicated that TiAlN exhibits a highly textured fcc structure with a dominant (111) orientation, while ZrAlN presents mixed phases of poorly crystalline cubic ZrN and orthorhombic Zr3N4. Scanning transmission electron microscopy (STEM) revealed the columnar morphology with nanolayers alternating in Al content for both coatings. When integrated into a multilayer architecture – with insulation and wear-resistant layers – for cutting tools, both nitride sensors displayed distinct thermistor behavior, making β curve calibration challenging above 400°C. Nevertheless, during in-situ temperature monitoring of titanium turning, the cutting temperature was found to be predominantly influenced by the cutting speed (Vc) and depth of cut (ap), rather than by the feed rate (f). Additionally, it was found that the utilization of cooling is the most effective method for reducing cutting temperatures and that sensor positioning on the rake face is critical for capturing peak thermal data. |
|---|