The High-Quality Precision Casting of Titanium Alloys

Titanium Alloy is known for several amazing properties such as high specific strength, low density, corrosion resistance, high-temperature resistance, weldability, and much more. Studies reveal that it is one of the best materials that can be used for lightening as well as to enhance the comprehensive performance of powerful aerospace vehicles. Other than this, titanium products are preferred for many other applications such as ship, chemical industry, petroleum, biomedicine, leisure, and sports as well.

Casting is recognized as the most important technology for the hot forming of metal parts. Studies reveal that precision casting of titanium alloy is an advanced technique of designing titanium alloy parts. Experts use this technique to achieve structural integrity of various parts while simplifying the machining amount, improving assembly efficiency, omitting assembly welding of parts, stabilizing quality, and reducing the overall cost of using titanium.

Why it is difficult to cast titanium?

Titanium shows high chemical activity when it is placed ata high temperature; therefore, it is very difficult to control the quality of the ultimate product during this liquid metal forming process. It is important to understand that cast titanium is a very unstable substance, it is immune to both chemical corrosion and seawater corrosion. When used in its purest form, titanium reacts instantly to oxygen as well and ends up creating a protective layer on the top which is titanium oxide. Similar kinds of reactions occur when titanium alloy comes in contact with few other alloyed forms of this material.

It is also important to mention that when titanium alloy is heated, its reaction with oxygen becomes so violent that it can challenge the normal casting process. The molten titanium in this high-temperature state can react with the smallest part of oxygen present in the refractory compounds. Note that refractories are the special type of materials that are used to create investment casting molds. This highly reactive behavior of titanium with the ubiquitous nature of oxygen in the surrounding environment leads to a considerable challenge for the manufacturers. Therefore, it is important to find a reliable method to achieve titanium alloy casting.

Methods to cast titanium

Titanium alloy precision casting leads to the formation of a high-tech product that integrates the unique technology of chemical ceramics, metal materials, vacuum metallurgy, high-resolution non-destructive testing, computer-aided design, high precision processing, numerical simulation technology, and manufacturing technology.

At present time, only very few countries have mastered this technology. The titanium alloy precision cast parts are designed by using vacuum arc melting along with centrifugal casting. The process is executed in a lost-wax mold that is developed using specific kinds of materials that do not react with the molten titanium alloy. However, there are few disadvantages of using this method; the most important one is that parts formed with this technique have lower fatigue strength when compared to those that are designed using welded parts and machines. The main reason behind this decayed performance is the additional hard layer of oxygen-enriched substance on the casting surface. Other than this, the cast parts also come with nonuniform grain sizes. In order to reduce the surface hardened layer while achieving the desired range of mechanical properties, it is important to follow a reliable combination of molding, melting, and heat treating.

Another commonly followed technique for titanium alloy casting is using a chemically inert material in the process and graphite is the best example of this. The specific process of minimizing this mold reaction is rammed graphite casting. In this process, the graphite sand is mixed with pitch syrup and water, and then it is rammed against a specific pattern to design mold. This mold is further dried and baked to get rid of binding materials which ultimately leaves a pure graphite shell behind. This specially designed mold shell can be now placed in the vacuum environment so that molten titanium can be easily poured into this shell. Once the liquid material inside achieves desired solid finish, the graphite shell is simply broken down and we are left with the final cast titanium product. Other than this, many manufacturers also prefer using metal injection molding or titanium investment casting to design cast titanium products.