# Recent Progress Trend on Abrasive Waterjet Cutting of Metallic Materials: A Review
## 3 Abrasive Waterjet Cutting Process Parameters and Influences
### Abrasive Waterjet Cutting Input Process Parameters Functions and Influences
#### 3.1.2 Abrasive System  
The abrasive system is composed of abrasive material type, size, shape, and flow rate. The abrasive mass flow rate is the stream of its particles alongside waterjet pressure, which is typically measured in g/min [6]. Figure 4: Cause-and-effect diagram of AWJM process parameters [9,81]. **Impacts of abrasive type:** Abrasives are categorized into natural, zirconia alumina, glass, steel, and copper. These types have inherent diverse characteristics such as the level of hardness and grit shape. In particular, [PERSON] et al. [64] have conducted an experiment in cutting titanium using different abrasives, i.e., garnet, olivine, and crushed glass abrasives. Based on his experiments, garnet gave the highest material removal or cut penetration. Later, they carried out a comparative investigation between garnet and corundum abrasive. They concluded that corundum abrasive applications could be suggested within certain economic circumstances due to the decreased lifespan of focusing tubes [86]. Furthermore, it has been established that AWJ cutting performance is vastly affected by the density, shape, and hardness of abrasives. Table 5 exhibits categories of abrasive materials utilized in various industries, in conjunction with their details and properties. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Category Details** & **A. Glass** & **B. Natural** \\ \hline \hline \multirow{2}{*}{Abrasive types} & \multirow{2}{*}{Glass beads} & \multirow{2}{*}{Garnet} & \multirow{2}{*}{Ceramic beads} & \multirow{2}{*}{Black corundum} \\ \hline Hardness & MOHS 5–6 & MOHS 7–8 & MOHS 9 \\ \hline Shape & Round & Irregular sharp—edged \\ \hline Application & Grinding, polishing, drilling, cutting, tumbling media, sharpening, and metal cleaning \\ \hline Industrial use & Automotive, metal fabrication, machinery, electronic, construction, metallurgy, petrochemical \\ \hline
**Category Details** & & **C. Zirconia Alumina** \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Abrasive material categories along with their properties and industrial applications [1, 68, 87, 88]. AWJM has capabilities in machining hard-to-cut materials because of its abrasive particles. Table 5 showed a representation of each abrasive category characteristic, such as particle shape, hardness, application, and industrial usage. The zirconia alumina group of abrasives indicates dominance in hardness. [PERSON] et al. [89] have linearly machined high-carbon steel DIN norm No.1.2436 (CSN EN 19437) plate 61-mm-thick using seven different abrasives: Australian garnet, Ukraine garnet, olivine, corundum, chromite, and zirconium sized from 200 to 300 \(\upmu\)m, and unsorted Australian garnet. They discovered that corundum, which was approximately equal to garnet, increased cutting speed at 20%. Garnet has a comparatively low wear of focusing tubes when utilized [90]. A survey reported that 90% of users employ garnet as an abrasive type during AWJM applications [4]. Other reasons behind the high usage of garnet are attributed to its competitive price of approximately 0.48 \(\upxi\)/Kg [24]. However, the economic concern should be weighed against abrasive performance. Hence, the abrasive type is governed by the hardness of the workpiece [17]. Therefore, a harder workpiece requires a harder abrasive particle. In general, abrasive hardness directly exerts MRR and the depth of cut on the material; accordingly, a harder abrasive indicates higher MRR and DOC, leading to a higher machining efficiency. Impacts of abrasive size: Abrasives come with varied sizes or mesh corresponding to their specific conditions or grades. The particle grain mass and volume directly impinge on kinetic energy, which influences AWJM output parameters [91]. Various mesh numbers with the corresponding mesh size and grade are summarized in Table 6.  
The selection of an appropriate abrasive size and type depends on the hardness of the workpiece [92]. [PERSON] et al.