1. Introduction
Cladding is a common surface coating technique in which a thick layer of material covers a relatively low-cost structural material to enhance its mechanical properties, corrosion resistance properties, and to improve the service life [
1]. The deposition is typically of superior quality, enhancing the mechanical and microstructural properties of base metal. With a refined microstructural arrangement in the top surface, the cladding material usually has the properties to withstand high temperature, impact loads, and high wear resistance.
Due to corrosion and wear resistance of martensitic and austenitic stainless steels, they are widely used in several engineering elements of hydropower plants and gas turbine plants [
2], but the hot and cold cracking of these materials makes martensitic stainless-steel fusion deposition a very difficult process [
3]. The contrast between friction stir processing (FSP) and manual metal arc welding (MMAW) was emphasized on low carbon steel cladding with AISI 410, and it observed that the hardness and wear resistance in FSP was better [
4] than MMAW. Several claddings, such as Al/ferritic stainless steel, stainless steel/carbon steel [
5], austenitic stainless steel/Al/Cu [
6], and stainless steel Ti/ferritic steel [
7] are common for industrial applications. These claddings are done by weld cladding, laser cladding, thermal spraying, brace cladding, and explosive cladding. Microwave cladding is a new technique which has the advantage of low thermal distortions and low porosity [
8]. It has also been reported that a hardness of 530 HV (51 HRC) was achieved using the microwave cladding [
8].
Weld cladding by metal inert gas welding (MIG) process is the most common and economical cladding process practiced in industries. Various metals such as nickel and cobalt alloys, copper alloys, alloy steels, etc. [
9] are used for weld surface cladding. Gas metal arc welding GMAW (MIG) is widely accepted by industry because of certain distinct benefits [
10,
11] but diminished spattering and no slag makes MIG to be more favorable. It has been reported that the GMAW (MIG) cladding system has high reliability, all position flexibility, and high production rate. Additionally, MIG is ferrous and non-ferrous materials friendly, clean, inexpensive, and does not use flux [
12]. These factors made MIG to be easily adopted by manufacturing units. Furthermore, the shielding gas in MIG protects the deposition of the weld from damage resulting in very high-quality weld deposits.
One of the most important aspect in cladding is the weld bead penetration. A minimal weld bead penetration is always favorable as it minimizes the dilution level. Cladding involves joining of dissimilar materials, and hence cracks are formed in the fusion zone of two materials due to different thermal expansion coefficients [
1]. A suitable clad bead geometry depends on the input of weld heat (current, voltage, and travel speed). It was observed that the corrosion rate for austenitic (316) stainless steel cladding on low alloy steel at moderate to low heat input was minimal [
13]. In the case of a low alloy base material, the austenitic stainless-steel cladding exhibited maximum resistance to corrosion at travel speed of 145 A, 26 V, and 535.8 mm/min [
14]. The duplex stainless-steel deposition on low carbon steel at 0.38 kJ/mm heat input provided a desirable microstructure and a minimum corrosion rate [
15]. Dhib et al. [
16] reported the formation of decarburized ferrite zone and carburized austenite zone while cladding A283 with AISI 316 by hot rolling process. This was due to the transfer of elements from base material to clad, which in turn formed a diffusion layer. Cracks were mainly observed in the base material, but the bonding of base metal and cladding was sufficiently good. Also, Dhib et al. [
17] reported the presence of diffusion layer between clad layer and parent metal during cladding with austenitic stainless steel on low carbon steel also. Additionally, they found that, as a result of carbon diffusion from the base metal and microstructure, grains near the straight interface were elongated perpendicular to the welding direction, which resulted in a change in near-weld interface micro-hardness [
17]. The cladding of AISI 308L with laser cladding process on AISI 316 showed a reduction in heat affected zone and also a good metallurgical bond, but the average hardness was found to be 236 HV(41 ± 2 HRC), while the substrate hardness was found to be 247 HV (43 ± 2 HRC) [
18].
The high wear resistance properties of AISI 410 and mostly all martensitic steels recommend them as suited materials for surface coatings and hardfacing [
4,
19,
20,
21,
22]. After careful grinding and flattening of the surface, it is always desirable to increase the number of deposited layers [
23]. In a single-layer approach, there is a dilution from base metal [
23], which decreases the hardness of the hardfaced layer and ultimately decreases wear resistance. As each layer is reheated in a multi-layer cladding system due to the deposition of the layer above it, the grains are refined in the middle layer and micro-cracks are also visible in the microstructure [
24]. In several occasions, nitrogen additives were applied by replacing an amount of carbon with nitrogen by using flux-cored electrodes. This reduces the chance of retained austenite formation by increasing the starting temperature of the martensite and causing the formation of refined martensite laths, which are highly desired during hardfacing with martensitic stainless steel, conducting to an enhancement of mechanical properties [
25]. In order to prevent the impact of dilution, a thickness of 15 mm with five layers of deposition is generally practiced [
19]. It is to be noted that wear of the top cladding surface not only depends on hardness of the top layer but also on its microstructure [
26]. For applications such anti-ballistics, the strength of the weld deposits or weld joints is an important parameter [
27] and thus, microstructure plays an important role. Rao et al [
28] reported that the long-term exposure of the interface to high temperature will lead to grain coarsening and a brittle interface was found due to cast dendritic structure in the clad [
28]. Thus, the interlayer claddings are used to reduce the dilution effect and to enhance wear resistance, hardness etc. However, chances of metallic carbides formation also increases in interlayer claddings [
29]. Modern techniques such as explosive cladding and microwave cladding are being used in several manufacturing units. In explosive weld zones, fatigue life varies with temperature of exposure and time of exposure, resulting in grain growth and recrystallization in the sample as well as decarburization occurring at the interface zone [
30]. Microwave cladding is one of the most economical and proficient ways of cladding where uniform surface texture and properties can be obtained with uniform heat distribution throughout the clad, with good tribological properties [
31].
From the above discussion, it can be observed that many filler materials have been used for cladding process, from austenite stainless steel to martensitic stainless steel. Nonetheless, very limited work on the minimal layer thickness, wear characteristics and microstructural behavior of martensitic welded clads have been reported until now. In this paper, the microstructure, mechanical and tribological properties of AISI 410 (martensite) cladded on EN 8 surface were analyzed. As less brittleness compared to solid-state welding procedures can be achieved by MIG [
4], this technique was employed for cladding. Results of pin on disk tribological tests, 3D profilometer, scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) analysis are presented, underlining the efficiency of the proposed cladding process.