The surface of mechanical components should have good abrasion resistance, high strength, and other surface properties to extend their service lifetime. There are many methods to improve the surface property of a component such as plasma techniques, shoot penning, chemical vapor deposition and physical vapor deposition, and so on. The selective laser melting (SLM) is an advanced additive manufacturing technology, with the characteristics of a high degree of freedom in manufacturing, low cost, and high efficiency [
1]. However, various defects are easy to occur in the SLM specimens, such as oxides, voids, cracks, residual stress, balling, and porosities [
2]. Currently, there are many methods to improve the mechanical and surface properties of SLM specimens. The main way to improve the quality of SLM specimens are to change the process parameters of SLM, such as laser power, scanning strategy [
3], scanning speed, scanning space [
4], layer thickness [
5], particle size of powder, materials, and so on. Thijs et al. [
6] studied the influence of different scanning speeds with the alternating and the unidirectional scan vector on the microstructure of the Ti–6Al–4V alloy processed by SLM. Ortner et al. [
7] found that residual stress could improve the fracture toughness of steel. A traditional heat treatment process is also a method of the surface strengthening treatment of SLM specimens. The SLM specimens can improve their surface appearance and mechanical properties to meet the needs of specific components by grinded, electro-blasted, mechanical-polished, residual stress relieving, surface peening treatment, plasma techniques, heat treatments, and Hot-Isotactic Pressing. Löber et al. [
8] have studied different post processing techniques, such as simple grinding, electro and plasma polishing, and blasting with different grits, to improve the high-surface roughness (SR) characteristic of parts generated by SLM. Kamariah et al. [
9] studied the effect of heat treatments on the micro-hardness of 316L stainless steel parts. The physical vapor deposition technology, especially the multi-arc ion plating technology, has been less studied as a post-treatment method to improve the property of SLM specimens.
In recent years, TiAlN coating, fabricated by multi-arc ion plating technology because of its advantages of high hardness, high oxidation temperature, good thermal hardness, strong adhesion, low friction coefficient, and low thermal conductivity, is widely applied to improve the surface properties [
10]. Now, the development of TiAlN/TiN coating technology has changed from single-layer and single-component film to multilayer, gradient multi-component composite, and multi-function, which can improve subtract-coat adherence. Wei et al. studied the TiAlN/TiN multilayer coatings with different modulation ratio. Their results indicated that the modulation ratio effects the microstructure and properties of TiAlN/TiN multilayer coatings, which optimal process parameters would be quite favorable for industrial application in the future [
11]. S. PalDey and S.C. Deevi reviewed the single layer and multilayer wear-resistant coatings of TiAlN obtained by various physical vapor deposition (PVD) techniques [
12]. The TiAlN/TiN multilayer coatings were deposited on M2 high-speed steel (HSS) by arc ion plating with separate targets to decrease the unfavorable macroparticles [
13]. Yongqiang Wei and Chunzhi Gong studied the effect of pulsed bias duty ratio on the microstructure, mechanical, and wear properties of TiAlN/TiN multilayer coatings deposited on M2 high-speed steel by a pulsed bias arc ion plating system [
14].
The mechanical components manufactured by the existing SLM technology cannot totally meet the requirements of high precision and strength because of their defects. The surface mechanical properties of SLM specimens can be improved by using a TiAlN/TiN multilayer coating fabricated by multi-arc ion plating on the surface of SLM specimens. While different substrates have certain effects on the properties of the TiAlN/TiN multilayer coating [
15], the main factors affecting the property of TiAlN/TiN multilayer coating include the hardness of substrate, the surface morphology of substrate, coating process parameters, etc. Many studies have focused on the influence of coating process parameters on TiAlN coating. As mention before, SLM process parameters have an important influence on properties (especially hardness, roughness, surface morphology, porosity, etc.) of SLM specimens. That means, SLM process parameters will also affect the property of TiAlN/TiN multilayer coating deposited on SLM substrate. However, no scholars have studied how these process parameters affect the property and the mechanism of the impact. Therefore, the present work aims to explore the influence of different process parameters of SLM on the property of TiAlN/TiN multilayer coating plating on the SLM specimen and the mechanism of these influences. Taking laser power, scanning speed, and scanning space as factors, an orthogonal experiment was designed. The TiAlN/TiN multilayer coating plating on the SLM specimen fabricated by the process parameters on the orthogonal experiment can be obtained. The surface topography and property of substrates and TiAlN/TiN multilayer coatings were tested, the influences of SLM process parameters on TiAlN/TiN multilayer coating were analyzed, and the optimal process parameter was obtained. This study will provide another form of surface post-treatment for SLM samples. The optimal process parameter obtained can be used to manufacture the SLM specimen for TiAlN/TiN multilayer coating. The coatings can cover cracks and pin holes of the SLM 361L specimen and can prove hardness of the SLM 361L specimen and antifriction wear-resisting. The coated SLM sample can be applied to functional elements such as micro gear, robot joint, and aerospace.