79
STUDY OF MECHANICAL AND TRIBOLOGICAL BEHAVIOUR OF ALUMINIUMCOMPOSITES REINFORCED BY TUNGSTEN CARBIDE THROUGH POWDER METALLURGY TECHNIQUE
Manoj Kumar Patel Haldkar, T. K Mishra and Murali Krishna
Abstract - In this aluminum metal powder, specimen reinforced with o, 4, 8, and 12 Wt. % of WC were prepared by powder metallurgy route. Universal Testing Machine (UTM) was used to prepare these Al-WC specimens at compaction pressure 80KN. A muffle furnace was used to sinter these specimen at 620°C.An abrasive wear test was done on a pin-on- disc wear tester using silicon abrasive media of sintered specimens. These sintered specimens were characterized using scanning electron microscopy (SEM) along with dispersive energy spectrum (EDS), X-ray diffraction (XRD), and hardness. The result shows that hardness and wear resistance increase up to 8 wt. % of the optimum amount of WC and Al-8WC sintered specimen exhibits minimum wear loss and higher hardness due to refined microstructure and strong bonding between Al and WC. Cutting, ploughing, and fracture wear mechanisms were identified in the sintered specimen.
Keyword: Al; WC; abrasive Wear; SEM; XRD; hardness.
1 INTRODUCTION
Aluminum (Al):- Aluminum is the most useful material to produce lightweight components. It is found in the form of cryolite and bauxite on the earth.
Aluminum has good mechanical and corrosive properties. In addition, it is good conductive and corrosion-resistant material. Because these properties are widely used in industries in several applications like aerospace, automobile, marine sectors, and architectural construction, it is also used in the electrical transmission line. Hall–Héroult process is used to produce aluminum commercially.
1.1 Properties of Aluminum:-
It has a low density (2.7 g/cm3), but steel hasa higher density (7.9 g/cm3).
It is ductile and malleable in nature.
It has very soft and lightweight.
It is an excellent conductor of heat and electricity.
It has good corrosion resistance.
It possesses good tensile strength and toughness.
It possesses good thermal and electrical conductivity.
It is also insoluble in water and alcohol.
It is non-sparking and non- magnetic.
1.2 Metal Matrix Composite Manufacturing
Different techniques manufacture metal Matrix Composite-
(i) Liquid Phase (casting processes) (ii) Vacuum infiltration
(iii) Pressure less infiltration (iv) Dispersion Method 1.3 Powder Metallurgy
Metal powder is widely used to produce different lightweight components by metal powder processing. In the standard Powder metallurgy sequence, the metal powders are compressed into the desired shape in the Mould (Die Punch) and then Sintered to bond the particles into a hard, rigid mass.
Pressing is complied in a Press type hydraulic Machine using the punch and Die Mould tooling explicitly designed for the part to be manufactured.
Sintering is performed at a temperature below the Melting point of the base metal specimen in the furnace.
There are various fields where powder metallurgy components are used, such as Filter, oil-impregnated bearing, gear.
Limitations and disadvantages of PM
High tooling and equipment costs.
Metallic powders are expensive.
Problem in storing and handling metal powder.
Limitation on part geometry because metal powders do not flow laterally in the die during pressing.
80
Variation in density throughout part may be a problem, especially for complex geometries.
2 LITERATURE REVIEW
1. Sachit T. S. et al. (2021) investigated abrasive wear properties of aluminum (LM4) matrix reinforced with the varying weight percentage of WC tungsten carbide and tantalum- niobium carbide (TaC) (0.5, 1.0, 1.5 and 2wt %) hard nano particles.
Composite Specimens prepared by powder metallurgy route using clod compaction and sintering process.
Pin on disc wear tester was used for wear test at different load range between 1- to 40 step of 10 N and sliding distance ranged between 400 to 1000 m in step of 200 m and velocity 1, 1.5 and 2.5 m/s. These powder, smaples and worn-out surface were characterized by SEM/
EDS, TEM and XRD. Result showed by to 2wt% in the composite reduces the wear rate.
2. Ranjit Barua et al. (2020). The main objects of this paper are to find out the effects of copper addition on the porosity of eutectic Al-12 Si powder metallurgy alloy. This alloy is extensively used due to its unique properties in automobiles, such as pistons, rotary engine housings, liners, etc. to reduce the weight of the components and fuel consumption.
In this experiment six Al-12Si-xCu alloys with copper content of 0.5%, 1.5%, 2.5%, 3.5%, 4.5%, 5.5% are produced. It is observed that the sample's porosity increased with increased copper content and porosity is maximum in low compaction pressure.
3. A. M. Sadoun et al. (2020) Investigations on the experimental examination on the additions of Al2O3 coated Ag percent on the properties of Cu–Al2O3 coated Ag nanocomposites. With the object of enhancement dispersion of high weight fraction of Al2O3 nanoparticles and wet ability in Cu matrix, nano Al2O3 particles were electroless coated via Ag particles. Four different Al2O3 content, 3, 6, 9, and 12 wt.%, are considered to highlight its effect
on the characteristics of the fabricated nanocomposite. High- energy ball milling is applied for mixing powders and compaction, and sintering are applied for consolidation. Micro structural explanations displayed a homogenous distribution of Al2O3. The relative density decreases with increasing the content of Al2O3 nanoparticles. In addition, micro hardness is increased gradually via the addition of nano Al2O3 coated Ag. Sliding wear rate decreases by increasing the Al2O3 coated Ag nanocomposite content and increasing the applied load. Also, the coefficient of friction decreases via increasing the nano Al2O3 coated Ag nanocomposite content and increasing applied load.
3 METHODOLOGY AND
EXPERIMENTAL WORK
This chapter aims to deliberate the methodology used in this work comprising a selection of powder, die punch design, and experimental techniques.
Figure 3.1Outline of experiments 3.1 Die & Punch Preparation
Die steel was used to prepare a cylindrical specimen by using a lathe machine in the GGITS workshop. A detailed drawing is shown in Figure 3.2.
81
Figure 3.2 Die and punchAs per the pin and disc tester standard, the diameter of the pin(sample) can be between 6 mm to 12 mm. However, as the powder preforms should have sufficient contact area with the disc, the pin diameter was 12 mm.
4 RESULT & ANALYSIS
The goal of this chapter is to study and investigate the data obtained by the experimental process. The experimentation is synthesized to analyzing the effect of WC content on wear, and frictional properties, hardness, Porosity of specimen have been investigated. Hardness and Porosity were also investigated.
4.1 Feedstock Powder Characterization Aluminum Powder possesses an approximately spherical shape, whereas WC feedstock particles have a spherical shape. These spherical shape powders decrease the resistance during the sintering process and make perfect bonding.
Figure 4.1 Feedstock powder (a) Aluminum (b) Tungsten carbide 4.2 Sintered Specimens Characterization
Cross-sectional SEM images of Al-0WC, Al-4WC, Al-8WC, and Al-12WC sintered samples are shown in Figure 4.2(a- d).Excellent bonding was observed between Al and WC particles. The al-8WC sintered specimen exhibits high density, as shown in Figure 4.2 (c). The sintered microstructure images show that WC particles get diffused in melted Al during sintering in a muffle furnace. This results in decreasing the grain size of WC particles and forms dense microstructure.
When WC increases, the more than eight wt. %, some cluster structure forms, and WC is not mixed correctly in Al matrix, and some AL-WC mixture floated the upper surface of the matrix and formed amorphous structure as seen in figure 4.2(d). A higher amount of WC, more than 8 wt. %, also increases the separation of particles, increasing the pores and decreasing the density.
The 3-D morphology of the cross- section of SEM images of sintered specimens is shown in figure 4.3 (a-d).
82
Various peaks and valleys are clearly seenin 3-D images. The surface becomes smoother when WC is mixed in the matrix. Al-WC exhibits a smoother surface and dense microstructure when WC is mixed more than 8wt. % the roughness of surface increases due to extra amount of WC which is not absorbed by the matrix.
Figure 4.2 SEM images of (a) Al-0WC, (b) Al-4WC, (c) Al-8WC, and (d) AL-12WC
Figure 4.3-D morphology of SEM images of (a) Al-0WC, (b) Al-4WC, (c) Al-
8WC, and (d) AL-12WC
Energy dispersive spectrum (EDS) of the Al-4WC, Al-8WC, and Al-12WC sintered specimens are shown in Figure 4.4 (a-c) and confirmed the presence of different elements Al and WC. Some other elements O and C, are also seen, which formed during the sintering process.
Figure 4.4 EDS Images of Composite (a) Al - 5 Tungsten Carbide (b) Al- 8 Tungsten Carbide (c) Al- 11 Tungsten
Carbide
4.3 XRD of Sintered Specimens
X-ray diffraction (XRD) patterns of sintered specimens are shown in Figure 4.5. Al was identified as a significant peak, and WC was identified as a minor peak. During sintering, Al5W was also formed, which increases the density and makes the structure dense. No other phases were identified due to less WC, although WC decomposed in W2C during the sintering process when mixed in a higher amount.
83
Figure 4.5 XRD patterns of sinteredspecimens
4.4 Hardness of Sintered Specimens The hardness of the sintered specimens is shown in Figure 4.6. Initially, the hardness of sintered specimen increases with increasing of WC up to 8 wt. %. After that, hardness does not increase with increasing with WC. Al-0WC, Al-4WC, Al- 8WC, and Al-12WC exhibit hardness in 61, 76, 80 and 72 Hv, respectively. The higher hardness of the Al-8WC sintered specimen can be attributed to refining and dense microstructure.
Figure 4.6 Variation in Hardness 4.5 Porosity Analysis
Porosity of sintered specimens are shown in Figure 4.7. Al-8WC sintered specimen exhibtsminium porosity and followed by Al-4WC, Al-12WC and Al-0WC sintered specimens. Al-4WC, Al-12WC and Al-0WC exhibts 100, 50 and 755 higher porosity than WC-0Al sintered sample. Minimum porosity of Al-8WC specimen is attributed to higher hardness and dense microstructure.
Figure 4.7 Variation in Porosity 4.6 Abrasive wear and coefficient The Pin-On-Disc wear tester (Figure 4.8) was used to test the abrasive wear test using silicon carbide 400-micrometer grit size comprise angular shape mounted on the rotating circular disc by an appropriate adhesive. Magview-2010 software was used to measure the wear and coefficient of friction inbuilt on the wear testing machine. The weight-loss method was used to measure the wear test. The friction coefficient was measured for 400 seconds with variation of every 10 seconds. RMP and time were set by using the control panel. The load is transferred on the pin by the fulcrum and cantilever, where load penal is attached.
LVDT is fixed on the top of the fulcrum, which continues to measure the weight in microns.
Result suggests that wear is a function of the addition of WC and increases with increasing WC up to 8 wt.
% and then decreases. AL-0WC, Al-4WC, and Al-12WC sintered samples show 129%, 28%, and 71% higher weight loss than Al-8WC. This result indicates that Al-8WC sintered samples show minimum wear. The minimum wear of Al-8WC sintered samples is attributed to higher hardness and dense microstructure.
Figure 4.8 Wear of sintered specimens
84
Figure 4.9 Variation of coefficient offriciton
The variation of coefficient of friction of sintered specimens is shown in Fig 4.9.Initially, COF increases in a very fast manner due to less contact between pin specimen and abrasive media, resulting in higher tangential shear stress. As the sliding distance increases, the contact between the pin and abrasive media also increases, reducing the shear stress and making COF stable. The addition of WC increases the coefficient of friction. Al-8WC samples show higher COF, and Al-0WC exhibits minimum COF. Al-12WC sintered specimen shows fluctuated COF due to extra amount of WC which comes on the upper part of the specimen so separation of Al particles increases in the matrix.
The addition of Tungsten Carbide improved the wear resistance. As Tungsten Carbide contents increase, the intermetallic particulates dissolve in Al- Tungsten Carbide matric to enhance grain structure. It can be seen in microstructure due to refinement of grain boundaries, and structure wear resistance also increase.
Strong adhesion followed between Al- WC due to lesser weight of segment of WC. Al-0WCsintered specimen suffered severe surface damage and higher wear but as WC mixed, it dropped the surface removal rate because WC particles inhibit the metal loss.
4.7 Worn-out surface analysis
SEM images of the Worn-out surface of sintered specimens are sown in Figure 4.10. The cutting wear mechanism was seen in Al-4WC, and Al-8WC sintered sample and small grooves are also seen in
the surface of Al-8WC specimen worn-out surface. Ploughing wear mechanism was seen in Al-0WC seen in the worn-out surface due to the ductile nature of the Al-0WC specimen. The fracture wear mechanism was seen in Al-12WC due to the separation of Al particles in the matrix. Some Deep groove was also seen due to presence of amorphous region in the surface.
Figure 4.10 SEM analysis of worn-out surface of sintered specimen
85
5 CONCLUSIONFrom the experiment result in analysis following conclusions were finding out of Al-WC Metal powder composite.
The addition of WC refines the microstructure due to strong bonding between Al and WC particles. The al-8WC sintered specimen exhibits dense microstructure when WC is increased up to optimum addition of 8 wt. % the extra amount of WC flout on the upper surface and increases the separation Al particles.
XRD results confirm the presence of various major and minor phases of Al WC along with Al5WC, which increases the hardness of the matrix.
Hardness increases of sintered specimen up to optimum addition of 8 wt. % of WC. WC-8 WC shows higher hardness. Al-0WC, Al-4WC, Al-8WC, and Al-12WC exhibit hardness in 61, 76, 80 and 72 Hv, respectively. The higher hardness of the Al-8WC sintered specimen can be attributed to refining and dense microstructure.
REFERENCE
1. Sachit T. S. et al, Wear Behavior of Aluminum LM4Reinforced with WC and Ta/NbC Hybrid Nano-Composites Fabricated Through Powder Metallurgy Technique FME Transactions (2019) 47, 534-542 534.
