Prominent Achievements of Laser Surface Treatment of Martensitic Stainless Steel and Alpha-Beta 6/4 Titanium Alloy

Abstract

Conventional surface treatment processes are known to suffer from several limitations. Among them are energy consumption, complex heat treatment schedules and non-controllable heat affected zones. On the other side, when a high powered laser beam is used as a source of heat for surface treatment it will obviate most of these limitations. Laser surface engineering is one of these advanced surfacing technologies that receive growing interest to improve the surface properties of metals such as hardness, wear and corrosion resistance. Such treatments may be divided into two main categories: (i) those which only involve microstructural modification e.g. laser hardening and laser melting and (ii) other processes which lead to dual changes in microstructure and surface chemistry such as laser alloying and laser cladding. This paper comprises the experimental findings of two significant examples for laser surface engineering. The first study is concerned with surface hardening of AISI 416 martensitic stainless steel whereas the second study involves laser surface cladding of Ti-6Al-4V alloy. The outcome of the first work is a notable improvement of toughness at the same level of hardness and wear resistance as compared to the conventional hardening treatment. Additionally, the optimum condition for combined wear resistance, impact toughness and corrosion resistance was recorded at a laser heat input value of 21 J•mm-2. The second study is concerned with laser surface cladding of the titanium alloy with a powder blend composed of 60 wt% of WC and 40 wt% NiCrBSi alloy, by means of a high power Nd:YAG 2.2 kW laser. The best clad layers were obtained at a specific heat input of 60 J•mm-2. More than three-fold enhancement of the microhardness of the clad layers was achieved combined with a remarkable improvement of the alloy wear resistance.

Laser Surface Modification of TC21 (α/β) Titanium Alloy Using a Direct Energy Deposition (DED) Process

“…Metallographic samples were prepared using the standard procedures of mechanical polishing and etching with a solution of 6 mL nitric acid HNO 3 and 2 mL hydrofluoric acid HF (48% concentration) for 90 s [ 16 ]. Microstructures were examined using the Axiotech 30 optical microscope, (Lukas Microscope Service, Inc., Hillview Court, Mundelein, IL, USA), and QUANTA FEG 250 field emission scanning electron microscope (FESEM), Hillsboro, OR, USA, attached with an energy dispersive X-ray (EDX) microanalyzer.…”

“…Several studies have investigated the direct energy deposition process for different titanium alloys, especially the commercially pure titanium and the Ti-6Al-4V titanium alloys [ 15 , 16 ]. For example, Sampedro et al [ 17 ] investigated the defect-free coatings of Ti-6Al-4V and the mixture of (Ti-6Al-4V + TiC) on grade 2 titanium and Ti–6Al–4V alloys, respectively, which were created using the direct energy deposition process.…”

Impact of laser process parameters in direct energy deposition on microstructure, layer characteristics, and microhardness of TC21 alloy

“…The DED technique of titanium alloys has been studied by numerous researchers, especially in pure titanium [9] and Ti-6Al-4 V alloy [10]. A cladding powder of NiCrB-SiC reinforced with hard ceramic WC particles is the most widely applied on the titanium substrate as a high wearresistant coating.…”

Casting and Laser Surface Melting of 316L Stainless Steel from Scrap Resources

“…However, 316L stainless steel may be subjected to corrosion and lose its mechanical properties in harsh environment [2,3]. Therefore, improving the surface properties of 316L stainless steel via surface treatment to extent its usage in various applications can be one of the solutions to its successful reuse [1][2][3][4][5][6].…”

“…Numerous surface modification techniques have been developed such as thermal spray, induction hardening, pulsed laser deposition and laser cladding to improve the surface properties of stainless steel alloys without changing their bulk properties [5][6][7][8][9][10][11]. These techniques greatly improve the corrosion resistance and mechanical properties through grain refining or coating of ceramics protective layers [5][6][7][8][9][10][11]. Recently, more attention has been given to nanostructured surfaces [8,[10][11][12][13] to improve the properties of stainless steels.…”