Numerical Modelling and Simulation for Sliding Wear Effect with Microstructural Evolution of Sputtered Titanium Carbide Thin Film on Metallic Materials

Abstract

Titanium carbide materials are introduced into manufacturing industries for the reinforcement and surface protection of base materials due to their substantial ability to withstand severe environments, which include sliding wear, corrosion, and mechanical failures. A thin film of titanium carbide (TiC) is coated onto brass and copper substrates using the radio frequency magnetron sputtering (RFMS) deposition method. The coating process is carried out at constant processing parameters, which include a sputtering power of 200 W, a temperature of 80 °C, a deposition time of 180 min, and an argon (Ar) gas flow rate at 10 standard cubic centimetres per minute (SCCM). The coating, together with the base materials, is modelled and its behaviours are simulated using ANSYS Workbench R19.2 Academic, supported by Mechanical APDL solver for nonlinear finite element analysis (FEA). The deformation, equivalent stress–strain characteristics, and elastic–plastic properties of the coating are determined at applied loads of 60 N and 25 N and coefficients of friction (CoF) of 0.25 and 0.38 for the thin film deposition on brass and copper substrates. The sliding distance and the speed of the alloy steel ball used during the sliding wear operation are found to be 3 mm and 4 mm/s, respectively. The sliding wear modelling and simulation process are, however, designed for the ball-on-flat (BoF) wear technique with a dry sliding approach. Therefore, BoF wear simulations are also performed on titanium carbide–brass (TiC-Br) and titanium carbide–copper (TiC-Cu) conjugates for the evaluation of surface engineering applications such as cutting tools and in automotive, aerospace, thermomechanical, and biomedical fields. The ball used for the FEA wear simulation is made from alloy steel material (AISI 52100) with a radius of 3.175 mm.

1. Introduction

Certain industrial, manufacturing, and engineering challenges posed by material wear and mechanical behaviours have been discussed by only a limited number of researchers for the enhancement of surface engineering applications, such as cutting tools and in automotive, electronics, and aerospace industries. Titanium carbide (TiC) is a ceramic material, brittle in nature, and is deposited on brass and copper base materials to protect the surface, which, in turn, extends the life span of the base material. The deposition of TiC on brass and copper substrates was performed using the radio frequency magnetron sputtering (RFMS) process with varied processing parameters, such as sputtering power, temperature, time, and at a fixed argon (Ar) flow rate of 10 standard cubic centimetres per minute (SCCM). The magnetron sputtering process is the removal of particles from the surface of materials using energetic impact particle bombardment [1]. Due to the high hardness and strong resistance to wear properties of carbide transition metals such as TiC, it is used to coat steel tools for the longevity of the tools’ material used for cutting tool applications [2,3]. Thus, the magnetron sputtering process for thin film coatings onto the surface of metallic base materials is widely used to obtain greater wear properties for surface coating applications [4,5]. The tribological effects on the coated materials are investigated further in this study. This is performed by developing a numerical model, which simulates properties for wear behaviour on the material’s surface obtained using the magnetron sputtering process. The resultant numerical simulation can be used to evaluate coatings and materials in areas such as cutting tool applications and automotive manufacturing industries. A ball-on-disk tribometer (MFT Series, Rtec Instruments, San Jose, CA, USA) was employed to investigate the wear properties of the films in an environmental chamber (−100 °C to 1500 °C and 5% to 95% RH). The test was conducted using an alloy steel ball with a diameter of 6.35 mm. The applied load was varied, whereas the sliding speed, time, and sliding distance were set constant throughout the test.

Numerical simulation techniques are also performed on the fabrication of thin films, thereby necessitating the investigation of the stress distribution on the surface of the base materials to predict the effects during the deposition process. Finite element analysis (FEA) is a computer simulation technique widely used in engineering applications and is regarded as a quick simulation tool to determine the approximate mechanical properties of materials. Many researchers have investigated wear behaviours using numerical simulation methods to analyse materials being fabricated on a parent material for improvement in surface engineering applications. Singh et al. [6] developed an algorithm for simulation that evaluates the wear in sliding and rolling contacts. Ashkanfar [7] conducted wear property simulations for biomedical applications that were subjected to oscillating loads during operations. Rudnytskyj [8] also developed a numerical model using Comsol and Matlab Multiphysics to model the wear characteristics associated with tribology tests, such as linearly reciprocating block-on-flat dry sliding contact. Singh [9] on the other hand performed a numerical simulation analysis on a pin-on-disk (PoD) system using ANSYS Workbench 16.0 to evaluate the stresses within the permissible limit of the structural materials for surface applications.

The American Society for Testing and Materials (ASTM-G99, 1999) [10] is regarded as one of the standards’ wear test measurements used when investigating wear behaviour on materials, either coated or uncoated [11]. Deshmukh et al. [12] developed a mathematical model using APDL (ANSYS) R14.5 software to evaluate the cutting tool life of cemented carbide-coated austenitic stainless steel AISI 304. Their study investigated the influence of multilayer coatings on cutting tools by evaluating the life of the tools, surface roughness, and flank wear properties for turning operations on lathe machines. Multilayer coatings showed a better-layered structure when compared to monolayer-coated tools. Devanagari et al. [13] performed a numerical simulation study using pin-on-disk (PoD) wear equipment for the dry sliding wear behaviour of stainless steel AISI 2507 under different applied loads. Khot et al. [14] also carried out a numerical simulation using ABAQUS v.6.10 to evaluate stress–strain properties by pin-on-disk (PoD) under self-mated conditions. The objectives of the mentioned studies were to develop stress distribution parameters with sliding cycles for 316LN stainless steel using a rounded pin in contact with a metallic spinning disk. Sivitski et al. [15] also conducted a ball-on-disk (BoD) sliding wear simulation of TiCN and AlTiN coatings on different steel substrates for contact stress using finite element method (FEM) calculations using ANSYS Workbench 14.5. The results revealed that hard coatings perform better on more ductile substrates. Their paper reported the sliding wear effect of sputtered TiC thin film coated on brass and copper base materials analysed with the ball-on-flat (BoF) process, focusing on manufacturing industry applications. Properties such as total deformation, equivalent von Mises stress, equivalent elastic strain, maximum principal stress, maximum principal elastic strain, and contact pressure that occurred during the sliding wear process were evaluated. The modelling and FEA process were performed using the ANSYS Workbench R19.2 Academic Solver software.

Many researchers have evaluated various alloy materials for the enhancement of surface engineering applications using both experimental and numerical simulation analysis techniques. Mohsen Soori et al. [16] performed an FEM analysis and validated the results with an experimental study for thermomechanical and cutting tool applications. The study used a modified Johnson–Cook model using difficult-to-cut materials such as Inconel 718, titanium alloy Ti6Al4V, and nickel-base superalloy gH4133B. The thermomechanical properties of titanium carbide/copper–graphene (TiC/Cu-G) composites were investigated by Faisal Nazeer et al. [17] for elevated thermal packaging applications. Behnaz et al. [18] also conducted an experimental study of improved hardness and wear resistance of TiC deposited on titanium (Ti) using a laser surface treatment technique. Finite element (FE) simulation analysis and validation with the experimental study were performed for cutting tools and thermomechanical applications on brass (CuZn37) for micro-milling operations [19]. Balkrishna et al. [20] performed an FE simulation analysis that validated an experimental study for cutting tools (uncoated carbide cutters) and tribological applications with the addition of a coolant on a titanium alloy (Ti6Al4V). This research shows that a thin film of TiC was successfully coated onto brass and copper materials and that finite element (FE) simulation analysis could be used to investigate the associated sliding wear behaviour.

2. Materials and Methods

The materials used for the deposition process as well as the numerical simulation of a developed three-dimensional (3D) model for the sliding wear process are studied and presented in this section. Titanium carbide thin film was deposited on brass and copper substrates using a radio frequency magnetron sputtering process. The deposition equipment used for this study was an HHH-TF500 magnetron sputtering machine. A radio frequency magnetron sputtering (RFMS) process was performed to deposit TiC ceramic material onto the surface of brass and copper substrates. Brass and copper samples with dimensions measuring 55 × 18 × 3 mm³ and 100 × 23 × 1 mm³, respectively, were used. The TiC-Br- and TiC-Cu-coated materials were pre-cleaned and washed with acetone to remove grit before the deposition process. Before the coatings process, a 15- to 20-min pre-sputtering process was applied to make sure the surface of the acquired target material was perfectly clean, and the films were deposited at a working pressure of 4.68 × 10⁻² Torr. The thin film coatings were examined in non-reactive conditions using Ar (argon) at a gas flow rate of 10.0 and 10.5 SCCM (standard cubic centimetres per Minute). Friction and dry sliding wear tests were performed on a ball-on-disk tribometer (MFT Series). Wear behaviours of specimens were investigated using instruments from Rtec, equipped with computer-assisted image analysis software. The wear properties are a sliding distance of 3 mm and a velocity of 4 mm/s, respectively.

The coated materials were also modelled and simulated using nonlinear finite element analysis using the ANSYS Workbench R19.2 Academic Solver software. The surfaces of the thin film-coated materials were studied using a computer simulation technique for titanium carbide (TiC) films deposited onto brass and copper metallic substrates. A photographic image of the Rtec wear equipment and a schematic diagram of the sliding wear process are shown in Figure 1.

2.1. Modelling

A three-dimensional (3D) model of the wear tools with a thin film of titanium carbide deposited onto brass and copper substrates is presented in Figure 2. The model comprises a stainless steel receptacle, an alloy steel ball (E52100) of 6.35 mm diameter, titanium carbide-deposited thin film, and the brass and copper substrates. In this model, the wear tool slides back and forth, creating a wear track on the surface of the fabricated film.

2.2. Finite Element Analysis

The finite element analysis (FEA) technique is a numerical simulation process used to determine the properties of the coating/substrate conjugate system. This is used to investigate the coating and the base materials for sliding wear conditions. A titanium carbide thin film on the surface of brass and copper is subject to wear during the sliding operation, and stress distribution is determined on the surface of the base materials. The finite element analysis model was designed for the ball-on-flat (BoF) process to investigate the sliding wear behaviour for thin film coatings on metallic substrate materials.

2.3. Contact Tool Mechanism

The contact tool model involving frictional contact between the alloy steel ball (E52100) and titanium carbide thin film surface for the ball-on-flat (BoF) sliding wear test is operated with a coefficient of friction of 0.25 and 0.38 for the coated TiC-Br and TiC-Cu materials, respectively. The contact tool mechanisms for the coated thin film on brass and copper are presented in Figure 3.

2.4. Meshing

The model discretisation of the generated mesh for the coated film on brass and copper flat plate samples before wear simulation is illustrated in Figure 4.

The mesh is generated with a tetrahedral structure. The multi-zone methods produced meshing statistics of 208,995 nodes and 92,481 elements for the TiC-Br system, and 112,501 nodes and 48,410 elements for the TiC-Cu system.

2.5. Boundary Conditions and Load

Before the finite element simulation analysis is conducted, boundary conditions (BCs) for load onto the specimen must be specified for the simulation process. Figure 5 shows the boundary conditions for this ball-on-flat model system. The BCs include force and displacement, and assume a fixed support.

The force is applied at the model’s receptacle and fixed support at the bottom of the base material. This simulation is indicated in Figure 5 with displacement shown in the direction of motion chosen for the model.

The mechanical properties used for this simulation are given in

Table 1. Material properties used for the numerical simulation analysis [21,22,23,24].

Properties	Titanium Carbide	Brass	Copper	Alloy Steel (E52100)	Stainless Steel
Young’s Modulus (GPa)	497	110	130	203	193
Poisson’s Ratio	0.19	0.34	0.34	0.3	0.31
Density (Kg/m3)	4940	8730	8930	7800	7750
Bulk Modulus (GPa)	267.2	114.58	135.42	169.5	169.3
Shear Modulus (GPa)	208.82	41.045	48.507	78.231	73.664
Hardness Value (HV)	3200	80–140	35–38	690	82–1100
Coefficient of Thermal Expansion (1/°C)	7.6 × 10−6	1.67 × 10−5	1.67 × 10−5	1.17 × 10−5	1.2 × 10−5
Ultimate Tensile Strength (MPa)	258	500	220	760	460
Yield Tensile Strength (MPa)	120	200	117	690	250
Thermal Conductivity (W/m°C)	30.9	130	393.5	50.2	60.5

. The table lists the mechanical properties of titanium carbide, brass, copper, alloy steel (AISI) E52100, and stainless steel that were used for the numerical simulation analysis.

Considering the load application on the deposited thin film, stresses would be developed at the surface of the film coating on the brass and copper substrates. The following equation presents the state of stress (σ) at any point on the coated surface using the differential equilibrium Equation (1) [25]:

$$\left.\begin{array}{l}\frac{\partial {\sigma }_{xx}}{\partial x}+\frac{\partial {\sigma }_{xy}}{\partial y}+\frac{\partial {\sigma }_{zx}}{\partial z}+P_x=0\\ \frac{\partial {\sigma }_{xy}}{\partial x}+\frac{\partial {\sigma }_{yy}}{\partial y}+\frac{\partial {\sigma }_{yz}}{\partial z}+P_y=0\\ \frac{\partial {\sigma }_{zx}}{\partial x}+\frac{\partial {\sigma }_{yz}}{\partial y}+\frac{\partial {\sigma }_{zz}}{\partial z}+P_z=0\end{array}\right\}$$

(1)

where P_x, P_y, and P_z are the forces per unit volume acting along the directions x, y, and z, respectively.

3. Results and Discussion

A finite element analysis for post-processing generated in the ANSYS 2019 R2 Academic software is used to obtain the stress distribution on the coated thin film as well as the effects on brass and copper substrates. An augmented Lagrange formulation for symmetric behaviours with isotropic material properties as well as bilinear isotropic hardening was used for stress formulation. There was an expansion on the thin film’s surface during the sliding process, which could be attributed to the plastic–elastic deformation of the base materials when pressure is applied from the external body. The nonlinear finite element simulation analysis showed that several stress properties were associated with the sliding wear process such as deformation along the wear track, equivalent (von Mises) stress, maximum principal stress, and contact pressure.

3.1. TiC-Br Simulation Analysis

Figure 6 presents the simulation stress distributions observed during the sliding wear process of titanium carbide thin film deposited on the metallic brass substrate.

The results showed that the contact pressure during the wear process is much higher than the equivalent von Mises stress and maximum principal stress, whereas the equivalent strain and maximum principal strain are controlled by the coated thin film with little effect, which could be due to the outstanding properties of coated film such as high wear resistance property. In addition to the obtained simulation results,

Table 2. Maximum and minimum stress distribution for TiC-Br sliding wear process.

Value	Total Deformation (mm)	Equivalent (von Mises) Stress (MPa)	Equivalent Strain (mm/mm)	Maximum Principal Stress (MPa)	Maximum Principal Strain (mm/mm)	Contact Pressure (MPa)
Maximum	3.0169	6.4576 × 105	1.3007	1.5188 × 105	0.32666	1.1369 × 106
Minimum	0	4.9353 × 10−11	5.5713 × 10−15	−71,334	−0.021492	−13,166

presents the maximum and minimum values for stresses encountered during the sliding wear process. Figure 7 illustrates the behaviour of individual stress effects on the coated thin film.

Figure 7 shows the stress distribution between TiC-Br and TiC-Cu conjugates during the sliding wear process. The von Mises stress for the TiC-Cu-coated material is lower than that of TiC-Br, which could be attributed to the ductile properties of copper compared to brass. On the other hand, the TiC-Br-coated material performed better when compared to the TiC-Cu material for contact pressure. This is due to the strength of the brass’s sudden load.

3.2. TiC-Cu Simulation Analysis

Titanium carbide thin film deposited on copper metallic materials was numerically simulated for a ball-on-flat sliding wear process to determine the stress distribution on the thin film’s surface. Figure 8 shows the simulation results of the sliding wear for the ball-on-flat process.

It was shown that the maximum stress concentration occurs at the point of first contact between the steel ball and the film surface.

Table 3. Maximum and minimum stress distributions for TiC-Cu sliding wear process.

Value	Total Deformation (mm)	Equivalent (von Mises) Stress (MPa)	Equivalent Strain (mm/mm)	Maximum Principal Stress (MPa)	Maximum Principal Strain (mm/mm)	Contact Pressure (MPa)
Maximum	3.0016	1.8248 × 105	0.38951	1.6606 × 105	0.2936	2.7149 × 106
Minimum	0	2.0287 × 10−11	3.7176 × 10−15	−15,190	−0.016906	−711.83

presents the maximum and minimum values of stresses observed during the wear process.

The maximum and minimum values for stress distributions obtained for TiC-Cu during the sliding wear simulation process are presented in Table 3. The equivalent strain and maximum principal strain were lower when compared to the total deformation. Thus, TiC-Cu material showed a better response to equivalent strain and maximum principal strain when compared to TiC-Br.

3.3. Microstructural Behaviour

Figure 9 illustrates the TiC thin film coated on brass and copper base materials, showing the film structure distributed across the surface of the base materials. The two parallel (vertical) black lines shown in Figure 9b section the sample to the appropriate size for microstructural analysis. The scanning electron microscopy (SEM) micrographs of the deposited films are shown in Figure 9c,d. It was observed that both brass and copper substrates achieved a densely packed thin film of TiC structural grains. Columnar grains of TiC particles were identified in the TiC-Br sample after deposition of thin film and are shown in Figure 9c. The TiC-Br sample with traces of columnar grains will be susceptible to mild sliding wear defects when compared to the TiC-Cu sample without any traces of columnar grain even at higher magnification. Figure 9g,h show the SEM micrographs of adhesive wear properties, showing fully dense, strong bonds, and no traces of thin film peeling at different coefficients of friction and applied load for the wear tracks of TiC-Br and TiC-Cu samples.

Wear tests were performed on the coated samples using ball-on-disk (BoD) tribometer equipment for friction and sliding wear tests. The wear parameters used for the tribological test were a sliding distance, tool speed, and dwell time of 3 mm, 4 mm/s, and 0.1 min, respectively. The applied loads were varied, whereas the sliding speed, time, and sliding distance were kept constant throughout the wear test. The counter-body was made from alloy steel (E52100) with a diameter of 6.35 mm, which is unidirectionally slid against the face of a coated metallic material (flat disk) under normal loads ranging between 25 N for the TiC-Cu sample and 60 N for the TiC-Br sample. The test was conducted in an ambient air environment without any lubricant applied. The linear reciprocating test was conducted on TiC thin film coated on brass and copper specimens for surface manufacturing applications. The coefficient of friction (CoF) for coated brass materials was enhanced and proved to be more reliable when compared to coated copper materials under varied process parameters. The CoF for the TiC-Br sample was measured to be 0.25, and the CoF for the TiC-Cu sample was 0.38.

4. Conclusions

The thin film of TiC was successfully sputtered on brass and copper substrates and studied for adhesive wear using the ball-on-flat (BoF) sliding process. It was shown that the TiC-Cu system behaviour is better when compared to the TiC-Br system for equivalent von Mises stress. Conversely, the TiC-Br system controls the contact pressure from the wear tool on a thin film surface better when compared to the TiC-Cu system. This can be attributed to the fact that brass is an alloy of copper and zinc, which are both ductile. The difference in maximum principal stresses of the materials’ systems is not significant, which showed that the materials responded swiftly to wear. TiC thin film sputtered on brass and copper base materials serves as an effective surface coating due to its high wear resistance. These results prove that these materials can be used in engineering and manufacturing applications such as cutting tools, heat exchangers, aerospace, and automotive industries.

This paper also investigated the sliding wear behaviour and the effect of TiC thin film fabricated on brass and copper substrates for the improvement of material mechanical properties. Finite element (FE) simulation analysis from the ANSYS 2019 R2 Academic Workbench software package was used for the study. The wear behaviours were numerically simulated for stress distributions on the surface of coated materials, which includes deformation, equivalent von Mises stress, equivalent elastic strain, maximum principal stress, maximum principal elastic strain, and contact pressure, respectively. The maximum value of the equivalent von Mises stress for the TiC-Br material was found to be 6. 46 × 10⁵ MPa, and the maximum value of equivalent von Mises for the TiC-Cu material was 1.82 × 10⁵ MPa. Conversely, the maximum contact pressure values for TiC-Br and TiC-Cu materials were observed to be 1.14 × 10⁶ MPa and 2.71 × 10⁶ MPa, respectively. The wear behaviour of a TiC thin film coated on brass and copper metals was successfully shown at various applied loads for surface coating applications.