Interfacial Reaction Between Liquid Titanium and Oxide Mold Contained Alpha-Case Formation Phase During Investment Casting

2016 ◽  
pp. 387-392
Author(s):  
Seul Lee ◽  
Jea Eun Jeon ◽  
Young Jig Kim
Keyword(s):  
Interfacial Reaction ◽  
Investment Casting ◽  
Alpha Case ◽  
Liquid Titanium ◽  
Formation Phase

Interface Reaction between Ti3Al-based Alloy and Oxide Mold

2015 ◽  
Vol 816 ◽  
pp. 562-566
Author(s):  
Luo Qian
Keyword(s):  
Interfacial Reaction ◽  
Reaction Layer ◽  
Investment Casting ◽  
Interface Reaction ◽  
Element Distribution ◽  
Diffusion Reaction ◽  
Thick Wall ◽  
Mold Material ◽  
Thin Wall ◽  
Interfacial Reaction Layer

Ti3Al based alloys are light and high-temperature materials, having potential wide applications in the aerospace and the aeronautical industries. Molten Ti is lively, and it is easy to react with the mold material during in the investment casting, and hence to form casting defects such as α contaminated layer in the metal near the surface and gas porosity, resulting in the deterioration of the surface quality and castings mechanical properties. Therefore, the mechanism of interfacial reaction between Ti3Al-based alloys and mold is necessary to study. In this paper, the interface reaction samples of Ti-24Al-15Nb-1Mo alloy and ZrO2(Y2O3stabilized) mold were prepared by actually investment casting. Optical microscopy, SEM, EMPA and micro-hardness tests were used to study the microstructures at metal side of interface, consider the element distribution and discuss the interfacial reaction mechanism. The results show that there is interface reaction between Ti-24Al-15Nb-1Mo alloy and ZrO2(Y2O3stabilized) mold, and it belongs to the typical bilateral diffusion reaction. The elements of Zr, Y, O diffuse into molten metal, at the same time, the matrix elements spread to the oxide mold, then form interfacial reaction layer. It has been found that the interfacial reaction was not uniform in the whole interface. In the thick-wall of castings, the interfacial reaction layer was thicker, and in thin-wall, the interfacial reaction layer was thinner.

The influence of face coat material on reactivity and fluidity of the Ti6Al4V and TiAl alloys during investment casting

2017 ◽  
Vol 231 (1-2) ◽  
pp. 38-48
Author(s):  
Rui L Neto ◽  
Teresa P Duarte ◽  
Jorge L Alves ◽  
Tiago G Barrigana
Keyword(s):  
Investment Casting ◽  
Cast Alloy ◽  
Microstructural Analysis ◽  
Test Sample ◽  
Standard Test ◽  
Tial Alloys ◽  
Alpha Case ◽  
Brittle Layer ◽  
Alternative Materials ◽  
Face Coat

Ti6Al4V alloy belongs to the most significant alloys within the conventional titanium alloys, namely for producing turbochargers impellers and human prostheses. TiAl alloys, because of its attractive properties, such as half density of any nickel-based alloys and excellent high temperature properties, exhibit excellent potential for aerospace turbines and turbocharger turbines application. Investment casting is a near net shape process with great interest for these kind of complex parts, but the processing of these alloys using this technique is still a challenge. In spite of these advantages, these alloys are highly reactive in their molten state, reacting with the ceramic shells used in investment casting, forming a hardened and brittle layer called alpha case on the cast alloy surface, rich in interstitial elements such as oxygen. It is commonly accepted that yttria-based face coats are the best solution for minimizing metal mold reaction, but this ceramic oxide is very expensive. So, the aim of this work is to test alternative materials to produce ceramic shells face coats. A test sample simulating both compressor wheels and turbines was developed and assembled in a wax tree for alpha case and fluidity evaluation. Reactivity studies were conducted based on microhardness measurements and microstructural analysis of γ-TiAl and Ti6Al4V standard test samples, casted in shells with different face coat materials: fused Y2O3, ZrSiO4, Al2O3, yttria (6%) stabilized ZrO2 and yttria stabilized ZrO2 with 10% fine Y2O3 (3–7 µm). The results obtained showed that fused Y2O3 face coat eliminates the alpha case, although affecting the fluidity, and γ-TiAl castings have more misruns blades than Ti6Al4V castings.

Formation of Alpha-Case Layer During Investment Casting of Pure Ti and Ti-6Al-4V Using Comparative XRD and EXAFS Investigation

2019 ◽  
Vol 51 (2) ◽  
pp. 586-596 ◽  
Author(s):  
Thanachai Boonchuduang ◽  
Atipong Bootchanont ◽  
Wantana Klysubun ◽  
Penphitcha Amonpattaratkit ◽  
Atchara Khamkongkaeo ◽  
...  
Keyword(s):  
Investment Casting ◽  
Alpha Case

Wettability of Molten Ti on ZrO2

2011 ◽  
Vol 291-294 ◽  
pp. 625-628
Author(s):  
Ai Hui Liu ◽  
Bang Sheng Li ◽  
Yan Wei Sui ◽  
Jing Jie Guo ◽  
Yu Fu Zhu ◽  
...  
Keyword(s):  
Interfacial Reaction ◽  
Cross Section ◽  
Contact Angles ◽  
Argon Atmosphere ◽  
Pure Liquid ◽  
Stabilized Zirconia ◽  
Liquid Titanium

The wettability between pure liquid titanium and calcia-stabilized zirconia was studied in argon atmosphere. The micrographic observations made on cross section perpendicular to the interface using SEM showed that interfacial reaction occurred. However, the contact angles were larger than 90°within experimental duration.

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