Direct Recycling of WC-Co Grinding Chip

Abstract

Grinding is a finishing process for high precision, high surface quality parts, and hard materials, including tool fabrication and sharpening. The recycling of grinding scraps, which often contain rare and costly materials such as tungsten carbide (WC-Co), has been established for decades. However, there is a growing need for more energy-efficient and environmentally friendly recycling processes. Currently, grinding sludges, which are a mixture of abrasives, lubricants, and hard metal chips, are only treated through chemical recycling. Direct recycling (“reuse” of chips as raw material) is the most effective but not yet viable process due to the presence of contaminants. This paper presents an oil-free dry grinding process that produces high-quality chips (i.e., oil-free and with few contaminants, smaller than 60 mesh particle size) that can be directly recycled, as opposed to the oil-based wet grinding that generates sludges, which require indirect recycling. The proposed alternative recycling method is validated experimentally using WC-Co chips from a leading hard metals’ processing specialized company. The contaminant level (oxygen 0.8 wt.%, others < 0.4 wt.%), granulometry (chip D50 = 10.4 µm with grain size < 3 µm) and morphology of the recycled chips’ powder is comparable to commercial powders proving the research and industrial potential of direct recycling. The comparison of sintered products using recycled and commercial powder provided equivalent characteristics for hardness (HRA of 90.7, HV30 of 1430), porosity grade (A02-04) and grain size (<3 µm).

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

“…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 ]. In order to achieve the ideal particle size and other attributes of the finished copper powder product, it is possible to modify the grinding medium size and shape, milling duration, and milling intensities [ 105 , 106 ].…”

“…As a result, the particles undergo deformation and flattening, resulting in flattened particle morphology. Additionally, the repeated impacts and shearing forces contribute to the reduction in particle size, leading to smaller particles [ 103 , 104 ]. The microstructure of Tungsten was improved with the use of the BPR model developed by Wu et al [ 117 ].…”

Progress in Sustainable Recycling and Circular Economy of Tungsten Carbide Hard Metal Scraps for Industry 5.0 and Onwards

“…Processing technologies: The conversion of tungsten carbide scrap into reusable material (production phase, Figure 21) presents a notable obstacle owing to its exceptional hardness and resistance to wear (resistance against mechanical crushing) [15,92,98,99]. Conventional recycling methods, such as melting and casting, may not yield satisfactory outcomes for tungsten carbide (due to the low binder content) [11,15,138].…”

A Novelty Procedure to Identify Critical Causes of Materials Incompatibility

“…Improving the quality of materials and industrial products remains a challenge. It is still difficult to ensure the repeatability of the results under industrial conditions, mainly as part of special material processes [ 1 , 2 ]. It refers to the processing and production of products compatible with quality [ 3 , 4 ], in order for special processes to be realised based on the validated algorithm or method [ 5 , 6 ].…”