Abstract: In this research, wear optimization, hardness, and density were investigated for an AlSi10Mg alloy made by selective laser melting (SLM), and also an additive SLM process simulation was carried out. The quality and performance of the additive manufactured (AM) parts depends on the build orientation. A model based on an L9 orthogonal array of Taguchi design experiments was created to perform the wear characterization for the Al6061 and AlSi10Mg alloys. However, the wear and mechanical properties of the AlSi10Mg alloy showed better results than the 6061-cast alloys. Finally, the optimal process parameters at low wear rate and frictional force were found at a load of 20 N, a sliding speed of 200 rpm, and a time of 5 minutes. The obtained result at optimal parameter a low wear is 90 micrometers, and the frictional force was 3.6 N. The laser energy density was calculated based on the given process parameter as 150 J/mm3. The hardness of the SLM-AlSi10Mg alloy Vickers was measured for AlSi10Mg as 126±5 HV and Al6061 as 98±5 HV because of the very fine microstructure and fine distribution of the Si phase in AlSi10Mg SLM parts. The highest density achieved was 99.6% (2.660 g/cm3) and obtained defect-free components.

Keywords: Selective Laser Melting (SLM); AlSi10Mg alloy; Wear Characterization; Hardness; Density; Microstructure

The additive layer manufacturing is used for over 30 years and is now commonly used in a variety of materials [1]. The present lots of type’s production machines, but all are similar in the sense that produce 3diemnsional shapes by combining a number of 2D slice [2]. In the current years, AM was developed for "rapid prototyping” (RP) fabricating of metal parts by direct laser manufacturing (DLM), electron beam melting (EBM), and selective laser melting (SLM) [3,4]. Along with Al-based of AlSi10Mg alloy traditional casting alloy and high demand in a aerospace and automotive applications due to low thermal expansion, light weight, and excellent mechanical properties [5,6]. In addition, the AlSi10Mg alloy has proven to be highly suited for 3D printed samples environment for scientific measurement [7,8].The AlSi10Mg alloy an attractive combination of high thermal conductivity, excellent weldability, excellent corrosion resistance, and sufficient hardenability [9,10]. AM compares to traditional techniques such as the ability to quickly produce complex custom structures, high resolution, there are some clear advantages and accuracy with minimal material loss [11,12]. SLM is a newly developed additive technology based on laser powder bed fusion (LPBF) [13]. According to sliced CAD model (computer-aided design); complex free-form metal products are produced by layer-by-layer laser scanning [14]. The AlSi10Mg alloy was good weldability due to eutectic composition of Al and Si [15]. The increasing manufacturing of metal additive layer manufacturing (MALM) technology, especially new LPBF technology, from academia and industry on the determine best AM process for newly or existing CAD designed metal materials [16,17]. The transient thermal gradient behavior in SLM method is primarily controlled by the given process parameters such as layer thickness, scan speed, hatching distance and laser power [18,19]. Due to complex geometry metallurgical properties of SLM-AM, including various mass, modes of heat, and momentum transfer, the SLM process defects as balling effect, thermal cracks, and pores are show below unintended processing conditions [20,21]. The optimized of SLM process parameters can be used to achieve a highest quality of manufactured metal parts (such as perfectly crack-free and fully dense parts) [22]. The optimized technology for cost savings reduced manufacturing process steps, and design freedom [23]. This study presents pin on disc wear characterization of process optimization and mechanical (hardness and density) properties of SLM-AlSi10Mg alloys [24]. Three the mainly important of pin on disc parameters, load (N), sliding speed (rpm) and time (minute) were selected inputs for wear characterization [25]. This allows you to quickly identify the optimized processing and achieve high wear resistance by SLM-AlSi10Mg [26]. This research paper specializes an effect on of pin on disc wear parameters for after manufactured by SLM-AlSi10Mg [27]. The statistical investigational layout changed into followed to optimized parameters to minimize the cost, time, and material [28,29]. The mechanical assessments had been executed on samples synthetic the usage of optimized parameters that gave minimal wear and frictional force [30,31].

The AlSi10Mg alloy material consists of spheres of powder particles produced by a gas atomization process and the chemical composition of AlSi10Mg as shown in [Table 1]. The AlSi10Mg alloy powder is provided by SLM Solution Group AG in Germany. In the SLM printing process, the particle size distribution ranges from 20 to 63 µm as shown in [Figure 1a]. The circular specimen (diameter D=8 mm and length L=50 mm) was considered for the wear test as shown in [Figure 1b].

Table 1: The chemical composition of AlSi10Mg alloy.

Figure 1: a) Powder particle size destruction and b) wear specimen

The wear test circular-bar rod specimens were built by an SLM M280 (M280 2.0) system equipped with a 280 × 280 × 365 mm building platform and an up to 400 Watts continuous Yb: YAG fiber laser as shown in [Figure 2]. A beam focus diameter of 80 to 115 μm and a scan speed of up to 10 m/s, an automatic AlSi10Mg powder spreading on build platform device, an inert argon gas protection system, and a computer based system for control of process. The used laser power as P=225 W, scan speed v=500 mm/s, the hatching spacing h=100 μm, the layer thickness t=30 μm, build platform temperature considered as 1500C and wear samples fabricated in the horizontal direction as shown in [Figure 3]. The laser energy volume calculated by E = P/v × h × t [Eq.1], and the value of laser energy density was 150 J/mm3. The SLM production was performed in an inert argon atmosphere to avoid the pick-up of interstitial oxygen (lower than 0.2%).

Figure 2: (a & b) SLM schematic diagram and printing process based on process parameter.

Figure 3: (a & b) specimens on SLM build platform and printing time.

In this research work, optimization of process parameters on wear characterization of AlSi10Mg parts manufactured by SLM is studied and also done additive layer by layer simulation of given process parameters.

Additive simulation:

The additive layer-by-layer simulation is the most important part of SLM printing because it saves time, material, and cost. Based on the design of experiment parameters, additive simulation was done and the results are as follows: displacement of 4.349e-05m (0.04328mm), temperature distribution in the SLM printing process from minimum 764.4K to maximum 766.2K and von mises stress of 6.897e+04pa as shown in the Figure 4. From the [Figure 4], SLM process is layer by layer manufacturing process so it was must variation of every each layer.

Figure 4: Additive simulation (a) Von mises stress and (b) Temperature distribution layer by layer.

Wear characterization

As shown in [Figure 5], the wear rate and coefficient of friction (COF) are usually used to evaluate the friction behavior. [Tables 2 and 3] show the wear rate of SLM-AlSi10Mg under various loads of 20, 40, and 60 N, slide speeds of 200, 400, and 600 rpm, and time considerations of 5, 10, and 15 minutes. The sliding distance was kept constant and all experiments were conducted at room temperature. The experiments were conducted on wear tests for various materials such as Al6061 and AlSi10Mg. The wear tests were carried out by using Taguchi L9 orthogonal array on pin on disc equipment and the lowest wear and lowest friction were observed, which implies that the wearing of pin material mostly depends on the applied load and speed [3,6]. The sample is weighted before and after wear testing, and the same process is repeated for all the remaining samples. The wear rates of AlSi10Mg gradually decrease with the increase in slide speed from 200 to 600 rpm and load from 20 to 60 N [14,15] as presented in [Figure 6]. 

Figure 5: (a&b) Wear testing schematic diagram 

Table 2: Levels and their Factors for LPBF of AlSi10Mg alloy.

                           Table 3: used L9 orthogonal array as per DoE.