From Machining Chips to Raw Material for Powder Metallurgy—A Review

Abstract

Chips are obtained by subtractive processes such as machining workpieces and until recently considered as waste. However, in recent years they are shown to have great potential as sustainable raw materials for powder technologies. Powder production from metal chips, through the application of solid-state processes, seems to be an alternative to conventional atomization from liquid cooled with different fluids. However, chip material and processing have an essential role in the characteristics of powder particles, such as particle size, shape, size distribution and structure (4S’s), which are essential parameters that must be considered having in mind the powder process and the metallurgy applications. Moreover, different approaches refereed in the application of this new “powder process” are highlighted. The goal is to show how the actual research has been transforming subtractive processes from a contributor of wastes to clean technologies.

Recent Advancements in Material Waste Recycling: Conventional, Direct Conversion, and Additive Manufacturing Techniques

“…Increasing raw material and energy costs have led researchers to find alternative ways to recycle metal waste [127]. Chips are formed during machining operations like turning, milling, drilling, grinding, cutting, and sawing.…”

Producing Metal Powder from Machining Chips Using Ball Milling Process: A Review

“…It is often used as a substitute for steel balls in applications where the material being ground is highly abrasive or reactive [96].…”

“…The conversion of metal chips into powder requires intensive grinding. The chips can be milled for crushing under conventional conditions, with and without a cryogenic environment [ 96 ], to optimize the particle sizes and other qualities of the finished products [ 97 ].…”

“…Cleaning would be unnecessary if the chips were made using a dry machining operation. The machining chips are put into a ball mill together with the grinding medium in this process after being cleaned and dried to eliminate any impurities [ 96 , 102 , 103 ]. The chips are subsequently ground into a fine powder while the ball mill rotates using the grinding medium [ 9 , 104 , 105 ].…”

“… Alumina: Alumina is a ceramic material that is often used as a substitute for porcelain or glass jars. It is highly resistant to wear and corrosion and is often used for grinding materials that are abrasive or highly acidic [ 96 ]. Zirconia: Zirconia is a ceramic material that is highly resistant to wear and abrasion.…”