研究目的
Investigating the metallurgical response of GGG-60 nodular cast iron to laser transformation hardening and developing the concept of process efficiency as applied to laser transformation hardening.
研究成果
The study concluded that the combination of laser power density and travel speed must be optimized to dissolve carbides without dissolving graphite nodules for optimum surface properties. The maximum hardening ratio was found to be 15.3%. Overlapping laser tracks resulted in more uniform microstructure and hardness, with 50% overlap providing better uniformity than 20% overlap.
研究不足
The study focuses on GGG-60 nodular cast iron and a specific fiber laser setup, which may limit the generalizability of the findings to other materials or laser systems.
1：Experimental Design and Method Selection:
A fiber laser model YFL-600 with max power of 600 watt was used for laser transformation hardening. The focus distance was 10 mm, the wavelength 1080 nm, optical efficiency 78%, with M2 factor more than
2：Argon gas in the co-axial mode at 25 L/min flow rate was used for both shielding of the heated surface and for protecting the optical parts of laser system. Sample Selection and Data Sources:
GGG-60 nodular cast iron was used. The cleaning process before laser transformation hardening included grinding with a 600 grinding grit number.
3：List of Experimental Equipment and Materials:
Fiber laser model YFL-600, GGG-60 cast iron samples, grinding equipment.
4：Experimental Procedures and Operational Workflow:
After some initial test runs, beam travel speeds and defocus distance were chosen such that to arrive at a reasonable hardened area without melting the surface of the component. Two different levels of power densities at four different beam travel speeds were investigated.
5：Data Analysis Methods:
Microstructures were investigated by optical microscopy and scanning electron microscopy supplemented with Vickers micro indentation hardness measurements, under a 2 N load.
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