研究目的
To investigate the laser transformation hardening of commercially pure titanium using a continuous-wave Nd:YAG laser, employing full factorial design with response surface methodology to establish, optimize, and study the relationships between laser process parameters (laser power, scanning speed, focused position) and hardened bead profile parameters (hardened bead width, hardened depth, angle of entry of hardened bead profile, heat input, power density).
研究成果
The research successfully developed mathematical models using FFD and RSM to predict heat input, hardened bead width, hardened depth, angle of entry of hardened bead profile, and power density for laser transformation hardening of commercially pure titanium. Key findings include: scanning speed and laser power have significant effects on responses, with scanning speed positively affecting all responses. Optimum conditions were identified to minimize certain parameters while maximizing hardened bead width. The models are accurate with low error percentages, validated through confirmation experiments. The study provides a useful tool for optimizing laser hardening processes in industrial applications.
研究不足
The study is limited to commercially pure titanium sheets of 1.6 mm thickness and specific laser parameters (laser power 750-1250 W, scanning speed 1000-3000 mm/min, focused position -30 to -10 mm). The models are empirical and may not generalize to other materials or conditions. Microstructural analysis was qualitative, and further mechanical property testing (e.g., hardness, wear resistance) was not included.
1：Experimental Design and Method Selection:
A full factorial design (FFD) with three factors (laser power, scanning speed, focused position) at three levels each was used, resulting in 27 experiments. Response Surface Methodology (RSM) was applied to develop mathematical models for predicting responses.
2：Sample Selection and Data Sources:
Commercially pure titanium sheets (ASTM Gr.3 equivalent) with a thickness of
3：6 mm were used. Chemical composition:
Ti (balance), C (
4：011%), Fe (15%), V (029%), Cu (14%), O (1%), N (003%). List of Experimental Equipment and Materials:
Equipment included a CW 2 kW Nd:YAG laser source (wavelength
5：06 μm, from GSI Lumonics), a 120-mm focal optic, argon gas for shielding at 10 liters/min flow rate, silicon carbide abrasive papers for grinding, and an optical microscope (LM525 portable video microscope with digital micrometers, accuracy 001 mm, software based on LINUX OS 3). Materials included commercially pure titanium sheets and Araldite for mounting specimens. Experimental Procedures and Operational Workflow:
The titanium surface was cleaned, and experiments were conducted based on the FFD matrix in random order. A Gaussian continuous wave spherical beam configuration was used. Transverse sections of laser-hardened beads were cut, mounted, ground with SiC papers (from 120 to 1200 grit), and measured using the optical microscope to obtain bead profile parameters.
6：Data Analysis Methods:
ANOVA and regression analysis were performed using Design Expert software to develop and validate the models. Scatter diagrams and confirmation experiments were used to assess model accuracy.
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