| 摘要: | 這項研究旨在透過選擇性雷射熔化（SLM）技術將陶瓷TiN顆粒混合入馬氏體不鏽鋼AISI 420基材中，以提高其機械性能和抗腐蝕性。此外，該研究還提供了有價值的見解，同時優化加工參數並詳細揭示晶體學分析，以製備優質金屬基複合材料。
為了實現上述目標，首要目標是實現TiN和AISI 420粉末的均勻混合，減輕TiN顆粒聚集的趨勢。因此，確定適當的混合方法對於減輕凝聚和污染是至關重要的，確保混合物適合SLM工藝。隨後，通過預打印單軌道測試來獲得高質量的SLM樣品，以確定最佳的線能量密度範圍，然後打印三維樣品，以評估不同加工參數、TiN含量（0 - 5重量百分比（wt.%）、TiN顆粒大小（20 µm、2 µm和20 nm）、以及後熱處理對最終品質的影響，包括物理、機械和化學性能。詳細檢查了材料-加工-微結構-性能之間的複雜關係。
此外，該研究提出了一種統計方法，以優化SLM TiN/AISI 420樣品的機械性能，採用整合方法包括Taguchi - Grey Relational Grade - Principle Component Analysis（Taguchi - GRA - PCA）。這有助於在多個響應變量上做出決策，特別是與表面粗糙度、相對密度和硬度等機械性能密切相關的參數。一個關鍵目標是預測SLM樣品的最佳強度性能。
因此，我們提出了一種新穎的兩階段混合方法，使用己烷或乙醇溶劑進行混合和振動。此方法確保了創建無污染的混合物，TiN均勻分散，避免凝聚，作為SLM工藝的理想原料。此外，確定了0.45至1.25 J/mm 範圍的線能量密度（LED）以獲得穩定的單軌道。在151至525 J/mm3 範圍內確定了體積能量密度（VED），以製備高密度的樣品。
向AISI 420基材中添加不同TiN含量表明對SLM TiN/AISI 420零件的微觀結構、機械性能和腐蝕性能產生不同影響。 TiN含量低於1 wt.% 表現出機械和腐蝕性能的改善。相反，超過1 wt.% 的TiN導致機械性能與基材相比下降。儘管如此，TiN存在於AISI 420基材中顯著提高了其腐蝕抗力。
熱處理過程降低了所有SLM TiN/AISI 420樣品的硬度，儘管與建造狀態相比，拉伸性能和腐蝕能力增加。使用Taguchi-GRA-PCA分析，確定了實現最佳機械性能的最佳加工參數：350 W 激光功率，370 mm/s 激光掃描速度，0.07 mm 孵化距離和0.05 mm 層厚，用於1 wt.% TiN/AISI 420複合粉末。
在微結構分析後，最佳TiN顆粒含量在SLM過程中表現出顆粒在晶界內均勻分散。將TiN顆粒納入AISI 420基材帶來了幾個優勢，作為加固相以加強基材，並形成一層被動膜以增強其耐腐蝕性。研究發現，含有1 wt.% TiN加固的SLM TiN/AISI 420樣品，在250 J/mm3 的VED下達到了745 ± 20 HV 的峰值硬度，超過了已建立的基準。抗拉強度達到1822 ± 21 MPa，伸長率為6.41 ± 0.40 ％，最大韌性模量為99.7 ± 3.0 J/m3。
;This study aims to enhance the mechanical properties and corrosion resistance of martensitic stainless steel AISI 420 matrix by incorporating Titanium Nitride (TiN) ceramic particles using the selective laser melting (SLM) technique. Furthermore, this investigation provides valuable insights into simultaneously optimizing processing parameters and revealing the crystallography analysis for superior metal matrix composites in detail.
To accomplish the above goals, the primary aim is to achieve a uniform blend of TiN and AISI 420 powder, mitigating the tendency of TiN particles to cluster together. Therefore, identifying an appropriate mixing method is crucial to alleviate agglomeration and contamination, ensuring a consistent mixture suitable for the SLM process. Subsequently, high-quality SLM samples are attained through pre-printing single-track tests to determine the optimal linear energy density range, followed by the printing of three-dimensional samples to assess the effects of various processing parameters, TiN content (0 – 5 in weight percent (wt. %)), TiN particle size (20 µm, 2 µm, and 20 nm), and post-heat treatment on the final quality, encompassing physical, mechanical, and chemical properties. The intricate relationship between Material–Processing–Microstructure–XRD, SEM, EDS, TEM, EBSD, XPS thoroughly examine property.
Moreover, the study proposes a statistical methodology to optimize the mechanical properties of SLM TiN/AISI 420 samples, employing an integrated approach incorporating Taguchi – Grey Relational Grade – Principle Component Analysis (Taguchi-GRA-PCA). This facilitates decision-making across multiple response variables, particularly on parameters closely associated with mechanical properties such as surface roughness, relative density, and hardness. A key objective is to forecast the optimal strength properties of the SLM sample.
Consequently, we proposed a novel two-stage hybrid mixing method using the blending and vibration in hexane or ethanol solvent. This method ensures the creation of a contaminant-free mixture with homogeneous dispersion of TiN, avoiding agglomeration, to serve as the ideal feedstock for the SLM process. In addition, the Linear Energy Density (LED) was determined in a range of 0.45 to 1.25 J/mm to achieve stable single tracks. The Volume Energy Density (VED) in the 151 to 525 J/mm3 range fabricated a high density of samples.
Various TiN content added into the AISI 420 matrix indicated the different effects on the microstructure, mechanical, and corrosion properties of the SLM TiN/AISI 420 parts. TiN content below 1 wt.% exhibited improvements in mechanical and corrosion resistance ability. Conversely, surpassing 1 wt. % of TiN led to a decline in mechanical properties compared to the base material. Nonetheless, the presence of TiN within the AISI 420 matrix significantly enhanced corrosion resistance.
The heat treatment process decreased the hardness of all SLM TiN/AISI 420 samples, although the tensile properties and corrosion ability increased compared to the as-built state. Using Taguchi-GRA-PCA analysis, optimal processing parameters for achieving the best mechanical properties were determined: laser power of 350W, a laser scanning speed of 370 mm/s, hatch distance of 0.07 mm, and layer thickness of 0.05 mm for 1 wt. % TiN/AISI 420 composites powders.
Following microstructure analysis, the optimal TiN particle content demonstrated even dispersion within the grain boundaries of AISI 420 during the SLM. Including TiN particles in the AISI 420 matrix offered several advantages, as a reinforced phase to fortify the matrix and forming a second passive film of TiN with the initial Cr2O3 film to augment corrosion resistance. The findings revealed SLM TiN/AISI 420 samples, with 1 wt.% TiN reinforcement, achieved a peak hardness of 745 ± 20 HV at a VED of 250 J/mm3, surpassing established benchmarks. Tensile strength reached 1822 ± 21 MPa, with an elongation of 6.41 ± 0.40% and a maximum modulus of toughness at 99.7 ± 3.0 J/m3. Upon subjecting the SLM TiN/AISI 420 samples to post-heat treatment, the toughness increased to 118.0 ± 1.3 J/m3. The optimal SLM TiN/AISI 420 samples exhibited corrosion rate values of 92.8 ± 1.1 mm/year in FeCl3 and 0.78 ± 0.01µm/year in NaCl 3.5%, outperforming those of SLM raw AISI 420.
Overall, this study presents a comprehensive approach to the effect of laser energy, content, and size of reinforced TiN powders and the post-heat treatment on the properties of SLM TiN/AISI 420 samples. It also proposes initial optimization processing parameters to enhance the mechanical properties and corrosion resistance of SLM TiN/AISI 420. The findings of this study offer valuable insights for developing advanced metal matrix composites for various industry applications. |
