Comparison studies on mechanical and wear behavior of fabricated aluminum surface nano composites by fusion and solid state processing

Highlights

• Surface modification through TIG arc and Friction Stir Processing (FSP) method.

• Enhanced hardness and wear resistance of the surface composite layer.

• Selected regions can be suitably modified to have improved wear resistance property.

• Easier and faster process compared to conventional heat treatment methods.

• Effect of various applied load (30 N, 60 N and 120 N) on the Al5083 alloy, Al-B₄C FSP composite Al-B₄C TIG arc composite were evaluated during wear test.

Abstract

By way of increasing the wear resistance, the service life of the industrial components can be enhanced. Nowadays fabrication of surface composites plays a vital role in improving wear resistance. This study attempts to fabricate such surface composites by way of incorporating nano particles of Boron carbide into the Aluminum 5083 alloy by Tungsten Inert Gas (TIG) arc process (liquid state) and friction stir (solid state) process. Microstructural studies were carried out on the processed region to analyze the dispersion of reinforcement particles. Hardness survey and dry sliding wear tests at different sliding loads (30 N, 60 N &120 N) were carried out to investigate the effect of reinforcing particles. The hardness and wear resistance of the fabricated surface composite by both the processes are found to be higher than the base material. Friction stir processed surface composites are possessing higher hardness and wear resistance than that of TIG arc processed composites. The worn out surfaces of the composites and wear debris were analyzed through SEM studies to understand the wear mechanisms.

Introduction

Aluminum matrix composites are finding high technology applications owing to their excellent mechanical, wear and corrosion resistance properties [1], [2]. The useful service life of the components depends on the surface [3], [4], [5]. Ceramic particles were reinforced into the matrix by utilizing various techniques such as coating, hard surfacing, cladding, and electron beam irradiation [6], [7]. Choo et al. [8] have deposited TiC particles on the plain carbon steel plate using high energy electron beam irradiation technique for producing the surface composite. This composite exhibited 3 to 4 times higher hardness than the base alloy due to the presence of TiC hard particles. These processes create an excellent bond between the substrate and the composite. Dubourg et al. [9] have modified the surface by addition of copper and iron powders on the aluminum surface by laser cladding. The hardness of Al/38Cu-11Fe(wt%) hardness was 550 Hv_0.2 whereas the hardness of the nontreated sample hardness was 20 Hv_0.2. Presence of intermetallic compounds, grain refinement and hardened surface of the Al matrix improve the hardness of the composite. TIG arc surfacing is a cost effective process. It produces high thickness surface composite layer which comprises of intermetallic compounds. Metallurgical bonding nature is the specific advantage of TIG arc surfacing [10], [11].

Recently Gandra et al. [12] have fabricated SiC composite on the AA2024-T3 substrate by employing AA6082-T6 aluminum alloy consumable rods by friction surfacing process. Faying surface of the consumable aluminum rod has been provided with a 2 mm diameter hole to a depth of 20 mm. SiC particles were packed in the hole for reinforcement during frictional surfacing. The hardness of the composite coating was 110 Hv which is 30% higher than the base alloy. Friction surfacing leads to grain refinement due to continuous and discontinuous recrystallization process. The SiC particles strengthened the coating with improved hardness and reduced wear. Jiguo et al. [13] have used TIG arc source with Ni and Al powder preplaced on the Q235 steel plate to prepare the surface with Ni-Al intermetallics. Islak et al. [11] have fabricated AISI 1060 steel/B₄C surface composite by TIG arc method. Microhardness of the composite was 4 to 5 times higher than the base material. Similarly TIG arc source was used with Ti & Al powder preplaced on the Titanium substrate to form the titanium aluminide intermetallic compounds [14]. The hardness and wear resistance of the coated surface was improved about 3 to 4 times than base material. In another study conducted on AISI 8620 steel, SiC/C particles diffused on the surface by TIG arc method. The hardness and wear behavior of the modified surface was significantly improved [15].

In order to fabricate surface composite by solid state processing method, recently well known Friction Stir Processing (FSP) technique is used [16]. The composite processed through FSP can have thickness in the range of microns to several millimeters. The reinforcement particles are incorporated in the matrix by mechanical mixing without melting the substrate. Several investigators have produced the surface composite by FSP. Compared to other surface modification techniques, FSP provides better grain refinement and uniform dispersion of reinforcement particles in the matrix [17]. The reinforcement particles are preplaced in the grooves/holes on the surface of the metallic substrate plate and then processed with the FSP tool to form the surface composite [18]. Various second phase hard particles such as SiC, ZrO₂, CNT, TiC, Si₃N₄, TiO₂, B₄C and Al₂O₃ were used as a reinforcement in FSP [19], [20]. The thermal stability of the aluminum alloy was improved by the addition of SiC into matrix [21]. The hardness and corrosive behavior of Al5083 alloy were greatly improved by the addition of SiC/CNT and CeO₂ particles. The higher percentage of cerium oxide improves the corrosive resistance of Aluminum alloy [22], [23]. Soleymani et al. [24] have reported that there is a significant effect on the wear properties of the Al5083 based MoS₂ reinforced composites.

Increase in number of FSP passes increases the uniform distribution of particles in the matrix and reduces the clustering effect with enhanced mechanical and wear properties [25], [26]. The application of B₄C is used in the surface modification processes extensively especially to develop Al based composites. B₄C has its low density (2.52 g/cm³), high hardness and excellent thermal stability. Owing to its specific properties, it finds specific applications such as neutron absorption; high wear resistance, high impact resistance, etc. [27], [28]. The present work aims to fabricate the Al/B₄C surface composite by TIG arc and FSP method. The microstructural characteristics, microhardness and wear properties of the fabricated surface composites were compared. The friction and wear behavior of the composite at different sliding loads (30 N, 60 N & 120 N) were investigated and the results were compared with the base material.