不同包埋材料与铸钛过程中表面反应层的变化

背景：目前为止，对于氧化镁系和氧化锆系包埋料应用于纯钛铸造工艺中的对比研究还没有详细的报道，而磷酸盐系包埋料对铸件表面反应层分层明显可作为对照。 目的：分析不同包埋料对铸钛表面反应层的影响。 方法：分别用磷酸盐系、氧化锆系、氧化镁系包埋材料包埋并铸造规格为10 mm×10 mm×1 mm的纯钛铸件，用扫描电镜、能谱分析、X射线衍射、显微硬度和金相观察的方法对铸件表面的反应层进行检测。 结果与结论：用磷酸盐系、氧化锆系、氧化镁系包埋料铸出的铸件在金相照片中观察表面反应层的厚度分别是70，45，12 μm。3种铸件分别在距反应层最表面100，60，40 μm处硬度值明显减少，由此处向钛基体内部硬度值变化较平稳；反应层中主要元素Al、Si、O 的含量随着深度增加逐渐减少。与氧化锆系包埋料和磷酸盐系包埋料相比，氧化镁系包埋料与钛铸件的反应较轻微，反应层较少，对纯钛铸造过程中产生的污染少，说明氧化镁系包埋料是铸造纯钛工艺中最理想的包埋料。

Changes in surface reaction layers during titanium casting using different investments

BACKGROUND:So far, comparative studies about the application of magnesium oxide and zirconium oxide-bonded materials in pure titanium casting have not been reported in detail, but phosphate-bonded investment has an obvious stratification on the casting surface reaction layers, and can be used as the control. OBJECTIVE:To study the effects of different investments on the surface reaction layer of cast titanium. METHODS:Phosphate, zirconium oxide and magnesium oxide investments were embedded for pure titanium casting with specification of embedded 10 mm x 10 mm x 1 mm respectively, and the casting surface reaction layers were tested by scanning electron microscope, energy dispersive spectrometer, X-ray diffraction, micro-hardness and metallographic methods. RESULTS AND CONCLUSION:The surface reaction layer thickness of the castings which cast by phosphate, zirconium oxide and magnesium oxide investments in metallographic photos was 70, 45, and 12 μm, respectively. The hardness value of these three species castings was obviously reduced 100, 60 and 40 μm from the surface respectively; from this place to the internal titanium cast, their hardness value changed stably. Major element Al, Si, O content in reaction layer was decreased gradually as the depth of reaction layer increased. Compared with zirconium oxide and phosphate investments, the reaction between magnesium oxide investment and titanium casting was slighter, and reaction layers were less, moreover, there was less pollution in pure titanium casting. These findings suggest that magnesium oxide investment is the most ideal investment for pure titanium casting.