Selection And Inspection Of Titanium Castings: Key Details Analysis

The quality of titanium castings directly determines the reliability and safety of end products. Scientific material selection and accurate inspection are the core of quality control, and key details exert a profound impact on their performance, service life and cost.

 

 

(1) Clarify Service Working Conditions
Commercially pure titanium is applicable for general working conditions for corrosive environments. Corrosion-resistant  titanium alloys  containing molybdenum and palladium can be selected for harsh mediums.

The α+β type Gr5 alloy with excellent comprehensive performance is the first choice, and the β type Ti-6242 alloy is suitable for high-temperature components of aero-engines operating at 550~650℃ for load-bearing components in the aerospace field.

The α type titanium alloys or commercially pure titanium are selected for low-temperature applications to prevent embrittlement. α+β type or β type alloys with good thermal stability are used for medium and high-temperature working conditions.

Parts subjected to impact and alternating loads require high toughness and fatigue resistance, while components under static loads give priority to balancing cost and processability.

(2) Strictly Control Purity Indicators
Titanium has high chemical activity and is easy to react with impurities, which impairs its mechanical properties and corrosion resistance. It is required to control the purit in material selection, with the total impurity content less than 0.1%, hydrogen content ≤0.015% and oxygen content ≤0.15%.

Raw materials must comply with international standards, be accompanied by grade, heat number and composition certification with traceability. For fields such as aerospace and medical care, re-inspection with precision instruments is required, and the composition deviation should be controlled within ±0.02%.

(3) Consider Process Compatibility
Material selection for titanium castings must take processability into account to avoid choosing hard-to-form alloys and prevent defects such as blowholes and cracks. Investment casting prefers alloys with good fluidity such as Gr5;
some β type titanium alloys with poor processability should be used with caution. Meanwhile, a balance should be struck between performance and cost.

 

 

(1) Incoming Raw Material Inspection
Incoming raw materials must be inspected for grade, composition, appearance and internal quality to strictly prevent the put into production of unqualified raw materials. Spectroscopy and chemical analysis are used to strictly control the content of main elements and impurities, and instruments and sampling are standardized to ensure accuracy.

Visual inspection and ultrasonic testing are conducted for surface and internal defects, and unqualified raw materials are prohibited from use. Inspection archives are established to achieve traceability. After pretreatment, the particle size of sponge titanium is controlled at 5–20mm, and inclusions in master alloys are controlled below 10μm.

(2) In-process Casting Inspection
The core of in-process casting inspection is to monitor process parameters and reduce defects and scrap rates. For investment casting, the shell strength, air permeability and surface quality must be strictly controlled to ensure no cracks and complete dewaxing.

Roasting parameters are accurately controlled, and vacuum or inert gas pouring is adopted to prevent oxidation. During pouring, temperature and speed are monitored in real time to avoid slag entrapment and blowholes.

Uniform cooling is ensured after solidification to prevent cracking caused by internal stress. For new processes such as 3D printing, printing parameters and interlayer bonding quality must be inspected.

(3) Finished Product Inspection
Before delivery, titanium castings must undergo inspections of appearance and dimensions, internal defects, mechanical properties and coating quality.

Appearance and dimensions: Check for surface defects, ensure key dimensions meet the standards, and the defect depth shall not exceed 1/3 of the wall thickness tolerance.

Internal defects: Non-destructive testing methods such as X-ray, ultrasonic, penetrant and eddy current testing are adopted; the magnetic particle method is generally not applicable.

Mechanical properties: Test strength, plasticity, impact toughness, hardness, etc., and increase the sampling inspection ratio for key components.

Coating quality: Test adhesion, thickness and uniformity.

Defect treatment: Products with excessive defects are deemed unqualified; minor defects can be repaired, while repair is strictly prohibited at key parts. Re-inspection and archiving are required after repair.

 

 

Quality control of titanium castings requires the combination of material selection and inspection to avoid imbalance.

Enterprises tend to attach more importance to material selection than inspection, focus on finished products rather than the production process, or blindly select high-end alloys, which increases costs and causes performance waste.

 

For 3D printed castings, attention should be paid to printing compatibility, and inspections of interlayer bonding and porosity are necessary. Technologies such as CT and laser ultrasonic can be used to improve the accuracy of defect detection.

 

Baoji Ruihang Elaborate Material Technology Co.,Ltd is a manufacture of titanium and non-ferrous metal products, supplying plates,bars,forgings,wires,tubes etc. If you have a purchase plan, please contact us by email:Sam.Rui@bjrh-titanium.com.