Viability of selected agro-waste as case hardening materials for cutting tools – A review.

. Machining is an indispensable part of production technology with cutting tool. with cutting tool playing key roles in its operations. The demand for more efficient cutting tool increases continuously with technology. Most of the cutting tools in use are imported and the cost of replacement is high. This problem had resulted in series of studies into the development of cutting tools from indigenous materials, particularly agrowastes. This study was a review of the various tool development approaches using various agrowaste types. The challenges and recorded successes as well as gaps in knowledge have also been identified. Summarily, the use of cutting tools developed from steel types that have been case-hardened by agro wastes is a viable alternative that can be explored for use in machining technology.


Introduction
Multiple-point cutting tools are mechanical tools that are used to shape materials by eliminating extra material from the workpiece.The tool's cutting blades are positioned such that they make simultaneous contact with the workpiece, resulting in many chips in one pass.multiple point cutting tool design can vary based on the application, material being machined, and intended output [2].Multiple-point cutting tools are a crucial part of the manufacturing sector and are used to shape, cut, and machine a wide range of materials.These implements have many cutting blades or points that operate in unison to create the required shape or surface quality.The value of multiple point cutting instruments in the manufacturing industry cannot be overstated.They are used to create parts and products with high precision, accuracy, and quality, which are crucial in many sectors such as aerospace, automotive, medical, and defense [3].Different point cutting apparatuses play a imperative part in cutting edge machining operations, giving effective and exact fabric evacuation from work pieces.These specialized instruments are planned with different cutting edges orchestrated in a particular design, permitting for progressed efficiency, upgraded cutting execution, and expanded instrument life [4].The utilization of numerous cutting edges disperses the cutting stack, diminishing the strain on person edges and empowering speedier fabric expulsion rates.This in-depth see at numerous point cutting instruments will investigate their different sorts, applications, and points of interest [5].Multiple point cutting tools have been used to make complicated components with great precision and accuracy in sectors such as automotive, aerospace, and medicine.These tools are favored over single-point cutting tools because they remove material more quickly, resulting in higher productivity and reduced machining time.Furthermore, multiple point cutting tools feature many edges that may be resharpened or changed, improving their longevity and minimizing the need for frequent tool replacements [6].One essential advantage of different point cutting instruments is their capacity to improve efficiency.By having different cutting edges, these devices can lock in with the workpiece at the same time, coming about in higher fabric evacuation rates and decreased machining times [7].However, a few challenges with multiple point cutting tools includes heat production during machining (which can result in premature tool wear and failure), difficulty of chip evacuation when cutting materials that create lengthy and stringy chips (resulting in chip accumulation and workpiece damage) and cost of producing and maintaining multiple point cutting tools, which can be more expensive than single-point cutting tools [8][9][10].This study therefore reviews the various attempts at producing multiple point cutting tools from agro wastes to mitigate these highlighted challenges.

Machinability of Materials & Cutting Tools
Machining is the process of removal of excess material from a parent type to form a precise shape.The rating of the level of ease of machining a material is defined as its machinability.This is assessed using various parameters such as rate of material removal, surface finish, chip type formed e.t.c [8].A lot of factors could influence the machinability of a material.This factors rages from the properties of the material, cutting condition to the cutting tool used.The cutting tool used particularly could influence the surface finish, cost of production and ultimately productivity of any manufacturing industry, hence cutting tools play a vital role in the manufacturing industries.

Single-point and Multi-point Cutting Tools
A single point cutting tool has a single primary cutting edge and can execute material removal operation in a in just one motion.Predominantly, these tool types may possess more than one cutting point, but they can only execute one cutting activity per time.They most often have a main cutting point referred to as the principal cutting edge while other points are referred to as auxiliary cutting edges [10].They are affordable and easy to design or use.However, they have shorter life span because they are prone to high cutting temperatures and thermal damage.They generally therefore result in reduced productivity (Machininig and Machine tools-book).Multi-point cutting tools are however different as they have an advantage of longer tool life while ensuring a higher material removal rate and an increase in productivity.They are generally therefore the preferred tool type even though they come costlier than the single-point types [10].

Agro wastes and Importance
The importance of agricultural wastes as an enhancer for steel has recently received much more attention by researchers with several studies carried out to ascertain the viability of various agro waste types in serving this purpose.This is because the agricultural sectors generate a large amount of residue each year.If such trash is disposed of incorrectly and without following proper procedures, it can cause environmental contamination as well as harm to animal and human health [11][12].Animal waste, farm waste, waste from food production, harmful waste, and hazardous waste are all types of agro-waste [13].Although, a few endearing properties of agricultural wastes that makes them desirable have already been established, however high carbon content, significantly stands out among them all [14].

Agro waste types employed A. Coconut Shell
Coconut (Cocos nucifera L.) is an evergreen plant that bears fruit continuously for over 65 years.[5][6].Coconuts are grown on more than 10 million hectares in 92 countries throughout the world.Indonesia, the Philippines, and India account for around 75% of global coconut production, with India ranking second [7][8].Ultimate analysis results show that there is a high carbon content value (52.6%) available in the coconut shell.This value is opined may enhance cutting tool hardness when used for case hardening.However, large amount of oxygen (53.1%) present as well may prove to be counter-productive as it may increase the possibility of flammability of the cutting tool [8].

B. Eggshell
Eggshells are waste materials from agricultural products created by chick hatcheries, bakeries, and fast-food restaurants, among others, that can litter the environment, causing environmental difficulties or pollution that must be handled properly [15].It is scientifically shown that eggshell is mostly formed of calcium compounds, which are extremely similar to cement.According to the literature, eggshell ash predominantly comprises lime, calcium, and protein and may be utilized as an alternative raw material in the manufacturing of wall tile material, concrete, cement paste, and other products [16].Eggshell also contributes to the building sector by lowering construction costs and landfill waste while providing high performance in concrete characteristics and durability.Eggshells account for approximately 11 percent of the entire weight of an egg.It is mostly composed of calcium carbonate (as calcite), with trace amounts of magnesium carbonate, calcium phosphate, organic compounds, and water [17].The presence of calcium in abundance in the eggshell (Table 3) provided for more strength for any mix or compound the shells are added [17][18].
. , 01   According to the results of the investigation, uncooked rice husk contains a significant quantity of carbon (20.63%).This large presence of carbon could be harnessed for strengthening materials via case-hardening (Table 4).Atomic Absorbtion spectrometry findings reveal that rice husk ash includes a significant percentage of K2O and Na2O (Table 5).These contaminants, together with black particles, are linked to the carbon content of rice husk ash, as well as the raw rice husk's dark color.The examination of uncooked rice husk

Conclusion
The viability of coconut shell, egg shell and rice husk as case hardening agents for cutting tools has been reviewed in the study.The strengths of each agro waste has been discussed with their possible contributions if considered as a case hardening material have been highlighted.It is believed that the use of these materials for this purpose will not only encourage waste to wealth possibilities, but will also facilitate stronger cutting tool production, thereby ensuring better productivity and improved surface finish for machined materials.

Table 3 :
[17]ysis of Eggshell powder[17]Over half of the world's population relies on rice (Oryza sativa) as a staple diet (Ayub and Changani, 2018).In 2018, China was the world's leading producer with 209.6 million tons, followed by India and Indonesia with 177.65 and 54.6 million tons, respectively(Afolalu,  2022; Statista, 2021).The majority of these rice hulls are thrown or burned in open places, resulting in energy waste as well as land and environmental damage (Ghosh, 2013).As a result, attempts have been made to use rice hulls as an additive in a variety of materials and applications, including fuel for energy production, fillers in polymers and rubbers, catalytic support, adsorbent, and the creation of silicates and silicon materials (Shiva, 2020).