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Unlike conventional powder metallurgy techniques , selective laser melting ( SLM ) is characterised by its fully melting process and very high heating and cooling rates and little has been known about the influence of powder surface state on the SLM process .
 powder metallurgy, selective laser melting, SLM, melting, heating, cooling rates, powder, SLM, process
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:
 powder metallurgy, selective laser melting, SLM, melting, heating, cooling rates, powder, SLM, process