The susceptibility of titanium to oxidization poses a formidable challenge during laser materials processing, especially at temperatures exceeding 450°C. To counteract oxygen absorption, an effective shielding mechanism is imperative. Numerous shielding chambers have been explored, each with its shortcomings. This project introduces an innovative solution—a positive-pressure chamber, adept at rectifying previous design flaws and ensuring uninterrupted shielding during laser materials processing of titanium alloys, illustrated in Figure 1. The discussion culminates in the examination of an additively manufactured titanium sample crafted within this enhanced chamber, showcasing the practical implications of our shielding solution.
Research Highlights
- A new design has been put forth to enhance the gas protection of titanium alloys in laser materials processes, signifying a progressive step in refining the manufacturing landscape.
- The proposed design incorporates a flexible chamber that can accommodate various gas environments, including but not limited to nitrogen. This versatility enables tailored conditions for specific processes like laser nitriding, expanding the scope of applications for titanium alloy processing.
Challenges
In the realm of laser materials processing for titanium alloys, ensuring proper shielding is paramount due to titanium’s heightened sensitivity to oxygen absorption. The optimal solution involves the use of a gas chamber filled with a neutral gas such as argon, providing a secure environment for the laser processes. However, the challenge arises when implementing this chamber in systems employing motion systems, often robotic in nature. The dynamic movements of the robot hinder the seamless integration of the chamber. To address this, a pragmatic solution involves the use of a flexible plastic chamber, exemplified in Figure 2-A. Despite its adaptability, a critical issue emerges during prolonged laser operation for materials processing. Over time, the laser’s reflection induces a burnout punch hole in the plastic (Figure 2-B), leading to the chamber’s ignition. The intriguing question that follows is: why does this specific region of the chamber succumb to such burnout?
Our Solution
Normally, high-power laser heads are installed with a 6 to 10 degrees vertical tilt, as you can see in the Figure 3-A. This intentional tilt enhances the longevity of the optics by preventing the rebound of laser reflections. However, this approach will induce problems like the burnout demonstrated in Figure 2-B.
The initial phase of the design process centered on the crucial task of devising a protective mechanism to absorb reflected laser beams swiftly and dissipate generated heat effectively. In this pursuit, aluminum emerged as the material of choice due to its low specific weight and commendable thermal conductivity. The schematic depiction of the finalized protective plate design is illustrated in Figure 3-B. This innovative addition aims to fortify the shielding system, serving as a pivotal component in preventing the adverse effects of laser reflection, thereby ensuring the sustained integrity and performance of the laser materials processing system for titanium alloys.
In our pursuit of refining the gas shielding mechanism, a pivotal enhancement involved the implementation of a positive-pressure chamber. This innovative chamber design incorporates a strategically positioned small gas outlet, enabling a controlled purge of gas into the chamber. The purge rate is meticulously calibrated to surpass the intake capacity of ambient air, ensuring that the chamber remains impervious to atmospheric infiltration. This meticulous positive-pressure approach not only bolsters the effectiveness of gas shielding but also contributes to the overall robustness of the laser materials processing system for titanium alloys.
The meticulous design and modeling of the gas shielding chamber were executed through Computer-Aided Design (CAD) software, showcasing the detailed CAD in Figure 4-A. The chamber’s innovative configuration consists of two integral components—the segment affixed to the laser head housing the protective plate and the glove box securely fixed on the table. These components are seamlessly interconnected through the use of flexible plastic, ensuring a cohesive and adaptable structure. These two connect to each other using the flexible plastic.
The ultimate fruition of our design endeavors materializes in the assembled gas shielding chamber, eloquently portrayed in Figure 4-B. This integrated structure encompasses a glove box with transparent, glassy walls that offer the robot programmer and other operators an unobstructed view of the internal processes. Equipped with gloves, they possess the capability to fine-tune the processing environment within the box. A tangible testament to the chamber’s efficacy emerges in Figure 5, showcasing a cubic specimen additively manufactured within this environment. The shiny silver surface of the machined cubic part stands as a visual affirmation of the meticulous gas shielding implemented during the process, underscoring the success of our innovative approach in laser materials processing of titanium alloys.
Outcomes
- A novel gas shielding chamber tailored specifically for laser materials processing of titanium alloys was conceptualized and brought to fruition.
- The newly devised positive-pressure chamber showcased exceptional capabilities for prolonged operations while ensuring comprehensive protection against reflected laser beams.
- Demonstrating the practicality of the designed gas shielding chamber, a titanium cubic sample was successfully fabricated through the laser additive manufacturing process. This tangible outcome underscores the effectiveness of the current shielding chamber in facilitating precise and controlled laser materials processing for titanium alloys.
Related Publications
Analysis of sheet metal titanium laser welding shielding and its effects on mechanical properties
M. Khajezadeh, F. Eshraghi, Mohammad H. Farshidianfar, Anooshiravan Farshidianfar
31st Annual International Conference on Mechanical Engineering (ISME2023)