6983
In this study , the effects of laser power and scan speed on the relative density , melt pool depth , and Vickers hardness of selectively laser melted ( SLM ) maraging steel were systematically investigated .
 laser power, scan speed, relative density, melt pool depth, Vickers hardness, laser, SLM, maraging steel
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 laser power, scan speed, relative density, melt pool depth, Vickers hardness, laser, SLM, maraging steel