Different materials behave differently, because of their melting temperatures, surface tension, and specific heat capacity differences. In addition to these inherent physical properties, different materials require different thermal management strategies to control, for example, hardening and crack formation. These effects require tailoring of process parameters to each new material processed. Also, since the geometry of the deposit and the fixture used will affect the thermal dissipation and buildup of temperature, process parameters might have to be adjusted during deposition depending on the specific deposit and fixture. High-temperature-resistant materials are normally selected for laser cladding coatings. For this reason, the whole microstructural and mechanical behavior at high temperatures is fundamental for their potential application. Focusing on Co-based alloys, Eutroloy 16,006 was deposited showing clads without pores or cracking retaining high hardness up to 525 °C (de Oliveira et al. 2006). Stellite SF6 was deposited by preheating the substrate at 650 °C to avoid cracking and optimize residual stresses. The coating showed hardness up to 880 HV with the diffusion of Fe from the substrate leading to improvement in wear and corrosion properties (Jendrzejewski et al. 2008). If thermally cycled at 1050 °C, a strong modification of carbides morphology and precipitation is revealed (d’Oliveira et al. 2002). Tribaloy® T-800 shows similar hardness levels,  though its high-temperature corrosion susceptibility limits the application ranges (Navas et al. 2006). Diaz et al. (2012) have proved not only the possibility of performing coatings to repair or improve the properties of the Cr-Mo ASTM A182 F11 steel but also the fact that these layers can be obtained using the laser cladding process. Dendritic microstructures and free crack and porosity coatings were achieved in the case of Stellites® and Tribaloy® T-900, keeping the original properties of coating and substrate. Only Tribaloy® T-800 presents a crack for motion.  Preheating of substrate can reduce this tendency of cracking but not completely remove its formation.

The damage to the die surface due to cyclic thermo-mechanical loading is detrimental to the service life. To enhance the die life, it has been observed that cladding-based repair is superior to welding or thermal spraying repair techniques. In this study, an experimental study of laser cladding of H13 has been carried out. CPM 9 V steel powder has been deposited on the H13 tool steel plate for repairing the die surface damage using a CW CO2 laser in conjunction with the powder injection system. The effect of laser parameters on clad geometry and clad quality has been investigated (Kattire et al.2015). The hard vanadium carbide particles increase the clad hardness to an average of four times greater than the substrate hardness. It has been observed that compressive residual stresses are generated in clad, which is desirable for repair applications as it will impede the crack propagation resulting in enhanced die life.

To strengthen  Invar alloy,  nanostructured carbide-strengthened cobalt-based cladding layers were fabricated on an Invar alloy by laser cladding. The cladding layers contained cubic γ-(Fe, Ni) or Co-based solid solution and hard carbides such as W2C, Cr3C2/V8C7, CoCx, and niobium carbide at the grain boundaries. The clad- ding layers improved the wear and oxidation resistance of the Invar alloy without changing its coefficient of thermal expansion. The results indicated that the friction coefficient of composite coatings decreased by 28.6% compared with that of Invar substrate   (Zou et al.  2020).  An in situ synthesized high-volume fraction WC-reinforced Ni-based composite coating was fabricated on a mild steel substrate by using a high-power diode laser. Three kinds of single-layer coatings of different amounts of W + C powder and Ni60 powder and a five-layer coating with different amounts of W + C and Ni60 powders in each layer were prepared. This work showed that the multilayer coating possesses the highest hardness among all coatings, and the maximum hardness of the coatings was about 3.7 times more than that of the substrate. The gradient coating technology combined with the feature that WC particles were liable to sink in the bottom of the coating was employed as a new idea for preparing the composite coating free of pores and cracks (Shu et al. 2017).

Stellite 6 was deposited by laser cladding of two different chromium-bearing steel substrates (P91 and P22). The results showed less cracking and pore development for Stellite 6 coatings applied to the P22 steel substrate. Further, the Stellite coating on P22 steel was significantly harder than that deposited on the P91 steel. The wear test results showed that the weight loss for the coating on P22 steel was significantly lower than for the P91 steel substrate. The surface topography data showed that the surface roughness for the coating on P22 steel was much lower than for the P91 steel substrate. It is concluded that the residual C content for the deposit on P22 was higher, mainly because the lower concentration of strong carbide form- ers, compared to P91, reduced the extent of carbon loss in the deposit (Kusmoko et al. 2014).

NiCrAl-based coatings are optimal for high-temperature protection   (De Damborenea et al. 1994). Thanks to the formation of ceramic and metallic oxides on the surface of the specimen, which prevent the spread of alloy elements toward the exterior, and the entry of oxygen into the material, the coating exhibits superior high-temperature corrosion resistance.  NiCrBSi coatings show very high wear resistance at high temperatures (Guo et al. 2011). Hardness increases with higher concentrations of B, C, Cr, and Si (Conde et al. 2002). Laser cladding NiCrBSi/WC-Ni composite coating shows better high-temperature wear resistance than NiCrBSi coating, which is due to the formation of a hard WC phase in the composite coating. NiCr coatings show a degradation of properties around 600 °C (Yang et al. 2012). Results indicated that the laser-clad NiCr/Cr3C2 coating consisted of the Cr7C3 primary phase and γ-(Fe, Ni)/Cr7C3  eutectic colony, while the coating added with WS2  was mainly composed of Cr7C3  and (Cr, W)C carbides, with the lubricating WS2  and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of the two coatings both decrease with the increasing temperature, while both wear rates increase. The same behavior is described for NiMoSi coatings (Lu and Wang 2004). Aging of the coating at 800 °C leads to the gradual dissolution of the interdendritic eutectic Mo2Ni3Si  and subsequent formation of a dual-phase structure with equiaxed Mo2Ni3Si primary grains distributed in the NiSi single-phase matrix. Because of the strong covalent-dominated atomic bonds and high volume fraction of the ternary metal silicide Mo2Ni3Si, both the original and the aged Mo2Ni3Si/NiSi coating have excellent wear resistance under pin-on-disc, high-temperature sliding wear test conditions; although the hardness of the aged coating is slightly lower than that of the As-clad coating. NiCrAlY-based coatings show stability up to 1100 °C (Partes et al. 2008). The obtained results suggested that up to 450 h the system was able to form a continuous alumina layer that could protect the substrate from oxygen diffusion. The Fe addition can easily be accomplished in the laser cladding process by dilution of the Tribaloy® T-800 coating with the steel substrate. In this work, a comparative study of microstructure, hardness, and cracking susceptibility of low and high-diluted T-800 and T900 coatings deposited by laser cladding is presented. A lower cracking ratio is obtained for the T-900 coatings at the cost of a lower hardness and wear resistance. No noticeable effect on the cracking susceptibility of the T-800 is found due to dilution with the substrate. However, a change in its microstructure is observed giving superior hardness and wear resistance  (Tobar et al.  2008).  Intermetallic coatings have good high-temperature wear resistance under sliding wear test conditions (Chen and Wang 2004). The laser-clad chromium-alloyed nickel silicide coating has a rapidly solid-fed microstructure consisting of the Ni2Si primary cellular dendrites and a minor amount of interdendritic Ni2Si/NiSi eutectics. The intermetallic coating has good wear resistance under dry sliding wear test conditions due to the high hardness, refined microstructure, and strong intermetallic atomic bonds (Cai et al. 2003). The LC of single-tracks and 3D (three-dimensional) objects of the Ni3Al intermetallic was successfully prepared. Good metallographic characteristics and interface bonding were obtained. The coating microstructure consisted of γ-Ni3Al. The cladding of the Ni3A1 coating with small dilution into the substrate can be obtained only at the appropriate power density of about 2–8 J/mm2 under the laser scan velocity of 100–200 mm/min and the powder feed rate of ~ 3.8 g/min. The average micro-hardness of the laser-cladding coatings was HV0,1380–1400. The ability of the multilayer LC process to build the Ni3Al intermetallic coatings was successfully shown (Kotoban et al. 2014).

Under high-temperature oxidation tests performed in an air furnace at 1100 °C up to 200 h, the weight gain of NiCoCrAlY was significantly larger than those of Ni and alloy counterparts, and 50 times less than the weight gain of the substrate. This can be understood as a consequence of its larger Al content. Surface morphology was inspected by SEM-EDS, revealing a dense, stable, and continuous Al2O3 oxide layer with Ni, Co, Cr, and Y oxide inclusions. The percentage of these oxides is as low as 5% in the NiCoCrAlY coating, reaching about a 50% in the CoNiCrAlY one (Tobar et al. 2014).

By analyzing the deposition of Inconel718 powders, increasing the laser power and decreasing the scanning speed has been shown to significantly increase the width of the deposited bead, whilst increasing the powder feeding rate and decreasing the scanning speed has been shown to significantly increase the height of the deposited bead. Additionally, a decreased laser standoff distance and increased laser power significantly increased the penetration depth. The top surface straightness was significantly affected by the powder standoff distance where an increased positive distance increased the deviation in the top surface. The microstructure was mainly columnar with long dendrites growing epitaxially in the height direction. However, on the top surface, there was a thin section with a dendritically equiaxed structure. This structure was most probably formed due to a lower thermal gradient and the increase of solidification velocity caused by the convection with the shielding gas (Segerstark 2015).

Results indicate the use of the laser cladding technique as an alternative to plasma spray or HVOF methods, yielding fully dense coatings with metallurgical bonds to the substrate. According to the effect of the three factors on bonding strength, the powder type has the largest dependency, followed by scanning speed. The laser output power has minimal impact. The bonding strength with iron-based powder is much higher than that with nickel-based powder. The bond strength increases as the laser power increases. No obvious dependence of bonding strength on scanning speed has been found (Xu et al. 2015). Based on the background of the engineering application of automobile mold repair and surface strengthening, the effects of pro- cess parameters on the formation and microstructure of laser cladding nickel(Ni)- based alloy coating were studied (Yufan et al. 2020). The optimal parameters were: laser power of 2000 W, powder feeding rate of 15 g/min, and scanning speed of 4 mm/s. Under this process, the cladding layer and the substrate can exhibit good metallurgical bonding, and the cladding layer has fine crystal grains and a low dilution ratio. On this basis, different mass fractions of niobium carbide (NbC) powder were added to the nickel-based powder, and laser cladding was carried out on the surface of the die steel. The results show that with the increase of niobium carbide addition, the hardness of the cladding layer decreases, and the wear loss of the cladding layer decreases first and then increases. When the niobium carbide addition reaches 6 wt.%, the wear loss of the cladding layer is the least, and the wear resistance is the best.

Surface modification of Ti-6Al-4 V is necessary to surface to enhance its tribological properties. Multi-phase and multi-component coating development is one of the present research trends in the surface engineering arena. Dhanda et al. (2014) it was attempted to develop a multi-component coating by laser cladding process using a pre-placed powder mixture containing Ni5Al (50 vol%) + hBN (10 vol%) + B4C(20 vol%) + SiC (20 vol%) on substrate of Ti-6Al-4 V to improve its tribological performance.   A   nanostructured coating was formed with micro-hardness (780 HV0.05). X-ray diffraction (XRD) identified the presence of compounds like TiC, BN, TiB2, SiC, and intermetallics of Ni-Ti in the coating. The wear behavior of the composite coating was assessed by a ball-on-disc type wear and friction monitor at 10 N load at 300 RPM taking a track diameter of 5 mm. Specific wear rate and coefficient of friction ( μ) were found to vary from 0.6E-12 to 2.2E-12 m3/N-m and from 0.15 to 0.45, respectively, due to rubbing of the coated surface against the tungsten carbide ball.

Metal matrix composite (MMC) coatings were fabricated on Ti–6Al–4 V titanium alloy by laser cladding. Co42 self-fixing powder, B4C, SiC, and Y2O3 were employed as the cladding materials. Results showed that the laser cladding coatings were mainly reinforced by CoTi, CoTi2, NiTi, TiC, TiB2, TiB, Cr7C3, and Ti5Si3. The micro-hardness of the cladding coatings was equivalent to three to four times the Ti–6Al–4 V substrate. Laser cladding coating exhibiting outstanding wear resistance was fabricated with the addition of 20 wt.% B4C, 7 wt.% SiC, and 1 wt.% Y2O3. The wear resistance was enhanced by over ten times compared with the substrate (Weng et al. 2020).