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The nitrided steel powder was then processed by L-PBF , and the microstructure as well as the chemical composition were investigated by means of scanning electron microscopy and carrier gas hot extraction .
 nitrided, powder, processed, L-PBF, microstructure, as, as, chemical composition, scanning electron microscopy, gas
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:
 nitrided, powder, processed, L-PBF, microstructure, as, as, chemical composition, scanning electron microscopy, gas