• International Journal of Technology (IJTech)
  • Vol 14, No 4 (2023)

Coating Material Development by Pulsed Laser Deposition for JIS SKD61 Steel Insert Pins Used in Aluminum Casting Industry

Coating Material Development by Pulsed Laser Deposition for JIS SKD61 Steel Insert Pins Used in Aluminum Casting Industry

Title: Coating Material Development by Pulsed Laser Deposition for JIS SKD61 Steel Insert Pins Used in Aluminum Casting Industry
Rusman Kosasih, Dedi Priadi, Maria Margaretha Suliyanti

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Cite this article as:
Kosasih, R., Priadi, D., Suliyanti, M.M., 2023. Coating Material Development by Pulsed Laser Deposition for JIS SKD61 Steel Insert Pins Used in Aluminum Casting Industry. International Journal of Technology. Volume 14(4), pp. 833-842

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Rusman Kosasih Material and Metallurgical Engineering Department, Faculty of Engineering, University of Indonesia, Depok, 16424, Indonesia
Dedi Priadi Material and Metallurgical Engineering Department, Faculty of Engineering, University of Indonesia, Depok, 16424, Indonesia
Maria Margaretha Suliyanti Research Center for Photonics, National Research and Innovation Agency, South Tangerang, 15314, Indonesia
Email to Corresponding Author

Abstract
Coating Material Development by Pulsed Laser Deposition for JIS SKD61 Steel Insert Pins Used in Aluminum Casting Industry

A Pulsed Laser Deposition (PLD) technique is a type of physical vapor deposition (PVD) technology. This research is one of a series of PVD studies aimed at determining the best PLD coating that can minimize the damage of steel pins made of SKD61 with a hardness of 48±1 HRc. The study began with the dummy blocks from SKD61 as research samples, followed by PVD-PLD with three coating materials as alternatives: Al/Cr (70:30), Al/Ti1 (50:50), and Al/Ti2 (63:37), all without active gases (N and C). The procedures used to test the research findings were FESEM, SEM, XRF, EDS, Vickers, and Rockwell Microhardness. The experiments were conducted at the BRIN Fotonic Research Center and the PT AHM Laboratory. The PLD process lasted for 10 minutes and employed an Nd: YAG laser with a wavelength of 1064 nm, a Q-switch with a time delay of 180 s, a pulse energy of 70 mJ, and a vacuum pressure of 1.161.35 Torr.Based on the results of the coating study, an AlTi1 coating was found to be the most effective material coating. The coating consisted of amorphous particles with a size range of 10 nm to 20 nm The coating had a thickness of 23 µm, and the surface hardness was measured to be 474-523 mHv for the single-layer coating and 477-501 mHv for the multilayer coating. The materials in both single-layer and multilayer coating samples have the same hardness in ascending order: AlCr, AlTi2, AlTi1, with a Ti concentration rise from 0.7% to 3.7%. The impact of the Ti element is also crucial in increasing hardness, wear resistance, and roughness.

Coating material; Minimize damage; Pin SKD 61; PLD process

Introduction

    Physical Vapour Deposition – Pulse Laser Deposition ( PVD-PLD ) is a coating process that has been widely used since 1987 to generate superconductive thin films with high-temperature resistance, which are employed in superconductors, medical applications, and electric, magnetic, and protective layers (Bruncko et al., 2019; Duta and Popescu, 2019;  Lorusso et al., 2015; Krebs et al., 2003). It is sensitive to the target condition, pulse energy, wavelength, vacuum process, target lens focus distance, and gas condition (Subramaniam, 2015). A typical PLD process experimental setup includes five key elements: target, substrate, laser, plasma plume, and vacuum condition (Masood, 2014). PLD has been developed in the last 10 years to manufacture crystalline layers for ceramic oxide, nitride films, and metallic multilayers, as well as to synthesize nanotubes, nanopowder, and quantum dots.
     Pulse Laser Deposition – Neodymium-doped yttrium aluminum garnet (PLD-NdYAG) uses a laser beam to ionize the target material, which is then dispersed through a plasma arc generated during the laser irradiation process. The released ions are then deposited on a substrate as a thin layer made of 10-9 m nanosized particles, together with reactive gases (Katase et al., 2012; Eason, 2007). Some physical and chemical material characteristics can change dramatically on the nanoscale from those of bulk-structured materials with the same composition. For example, the theoretical strength of nanomaterials can be achieved, or quantum effects can appear; nanosized crystals have a low melting point (up to a 1000°C difference with bulk structures) and reduced lattice constants because surface atoms or ions form a significant fraction of the total number of atoms or ions, and surface energy plays a significant role in thermal stability (Balaskas et al., 2012; Katase et al., 2012; Pokropivny et al., 2007). Laser irradiance, Pulse Repetition Rate, and Liquid or Gas media also have important role for the deposition process (Khumaeni, Sutanto and Budi, 2019).
     Scholars have been intrigued by current research and uses of superconductive materials, prompting them to investigate their potential usage for protective coatings (Yang et al., 2018; Willmann et al., 2008). Furthermore, the aluminum casting industry has seen an increase in the demand for protective layers to deal with die soldering. Die soldering occurs when aluminum welds to the dies or mold surface, leading to die damage and component defects and thereby halting production. Repairs are expensive and add more than an hour to production time. Die soldering is scientifically described as a chemical reaction that occurs during die casting between molten aluminum and the die surface. This reaction happens due to the washout or removal of a protective layer, such as a coating or lubricant, on the die. At sufficiently high temperatures and pressures, a protective layer is broken when liquid aluminum comes into contact with the die surface (Han, 2015). There are several alternatives method to minimize die soldering. Researchers have been studying to use of alloying material (Kohlhepp et al., 2021), dies treatment method (Mochtar and Aldila, 2020), and coating method (Serekpayeva et al., 2022; Kukuruzovic et al., 2021).

    Han Qingyou and Viswanathan declare that coating the surface of the die is the most effective method to reduce soldering (Han and Viswanathan, 2003). The coatings must be resistant to molten aluminum corrosion (Saravanan et al., 2018; Wang et al., 2017; Dennis et al., 2015; Presuel-Moreno et al., 2008) and also oxidation (Pane et al., 2023). The  fluctuation of the solidus temperatures for an aluminum-iron-x system reveals that coatings comprising titanium (Ti), chromium (Cr), and manganese (Mn) are efficient for resisting molten aluminum because they tend to raise the critical temperature (TC) at which soldering occurs (Han and Viswanathan, 2003). Additionally, Studies suggest that TiN, CrN, and CrC coatings can create excellent physical barriers that prevent soldering in the aluminum casting industry. In addition, adding elements to the alloy that increase the thermal conductivity or decrease the liquid percentage can also reduce the occurrence of soldering. By performing thermodynamic analysis, other elements that increase thermal conductivity and serve as suitable coating materials can be identified.
Regarding the dimensional need of the automotive aluminum casting – machining component, which has a tolerance of +/- 50 m, the PVD and CVD coating method became good alternatives because of their coating result, which max 20 m thickness. PVD is chosen between these two methods because it has a lower working temperature, unnecessary to use toxic gases, has less process cost, and provides better coating properties (Oerlikon, 2012). PVD – PLD is being challenged to become a good alternative for a protective layer. This study attempts to determine which coating material has the highest performance for creating a protective layer on the surface of SKD 61 tool steel by using the PVD - PLD process. 

Experimental Methods

2.1. Substrate
    In the use of G4404-JIS hot work steel, steel plate samples (10x10x2mm2) manufactured of SKD61 (tool steels) were employed (Figure 1). The surface hardness acquired through heat treatment is in the 45-47HRc range. This SKD61 tool steel is used for making several components of Dies such as cavity set, die/mold base, slide core, ejector pin, ejector plate, and insert pin. These materials are supplied by PT Astra Honda Motor as the dies user. The samples were made by several steps. Milling using CNC Milling FANUC machine with rpm 2100, grinding using Surface grinding KURODA at rpm 2000, cutting using Cutting wheel METKON at rpm 1500, and polishing from #600 until # 1000 using Polishing STRUERS machine with sandpaper.

Figure 1 Steel plates SKD61 samples (a) single sample & (b) samples stock
2.2. Coating material variable
    The steel plates were coated with three different materials supplied by PT Oerlikon Balzers Artoda Indonesia at different ratios: Al/Cr (70:30), Al/Ti (50:50), and Al/Ti (63:37) (Figure 2) utilizing two distinct coating processes, single-layer, and multilayer. Single-layer and Multilayer are referred to as the various products from PT Oerlikon. As the first step of coating continuous research, we will use all materials as is without any treatment for gas application. This is related to the vacuum chamber condition of PVD–PLD at the laboratory, which has no gas installation. For the next research, we will be going forward by using N2 gas after the vacuum chamber modifying.

Figure 2 Samples of the two coating materials: AlCr and AlTi. a) single layer AlTi, b) multi-layer AlTi 50:50/ AlCr/ AlTi 50:50, c) multi-layer AlTi 63:37/ AlCr/ AlTi 63:37, (d) multi-layer AlCr/ AlTi 63:37/ AlCr
2.3. PLD Preparation
      The PLD-NdYAG experiment was carried out at a wavelength of 1064nm, with a pulse energy of 70mJ, Q-switch after a time delay of 180s, a vacuum pressure of 1.16~1.35Torr, and a lens focusing distance of 15cm (Figure 3). These settings are determined through experiments to get the optimum setup outcomes as shown by plasma production in the target coating material. The good plasma is the one which has a 2-3mm flame dia, solid, and silent sound. To investigate the impacts, the materials were categorized such as A1–A6 for single layer and A7–A12 for multilayer. The experiments were conducted in a vacuum chamber with dimensions of 9cm x 9cm x 12cm, using a 15cm focus lens to enhance the strength of the laser strike. A rotary motor was used to maintain a target rotation speed of 3rpm, while the target-substrate distance was set at approximately 1-1.5cm.


Figure 3 Laser plume: (a) 1064nm wavelength, and (b) Laser Q smart 850

Results and Discussion

       The samples were divided into groups to investigate the impacts of Al, Ti, and Cr and compare their alloy compositions with mechanical properties, i.e. the hardness of the coating layer (Figure 4). They were also divided into two groups based on coating processes (single-layer and multilayer) to see how the number of layers affected the same mechanical qualities. Table 1 shows the classification.


Figure 4 Visual examination of the SKD61 plates after PLD
Table 1 Sample grouping by coating materials and techniques

Coating Materials

Samples

Coating Techniques

Al/Cr (70:30)

A1, A2

Single-layer

Al/Ti1 (50:50)

A3, A4

Single-layer

Al/Ti2 (70:30)

A5, A6

Single-layer

Al/Ti1, Al/Cr, Al/Ti1

A7, A8

Multilayer

Al/Ti2, Al/Cr, Al/Ti2

A9, A10

Multilayer

Al/Cr, Al/Ti1, Al/Cr

A11, A12

Multilayer

3.1. FESEM test results
       Field emission scanning electron microscopy (FESEM, FEI Helios Dual Beam) was used to study the microstructures of the PLD coatings at 10,000x, 20,000x, and 60,000x magnifications. FESEM images (Figure 5 and 6) reveal the presence of extremely tiny particles, 10-20nm in size, with a thickness of 23µm~30µm. This particle size is predicted to open up several opportunities to discover mechanical characteristics that differ from castings containing Al-Si particles with normal diameters of around 110µm (Ishak et al., 2017; Pokropivny et al., 2007). In general, smaller sizes can have a bigger ratio of surface area vs volume than the normal size. In the end, it will bring more reaction at the surface of the nanoparticles (Ramahdita, 2011). Therefore, PLD may be used to create thin films, multilayers, nanotubes, nanofilaments, and nanosized particles (Christen and Eres, 2008). Furthermore, as shown in the cross-section of the coating, the coating film is 23µm~30µm thick, defining it as a thin film.