A study on the influence of substrate pre-heating on mitigation of cracks in direct metal laser deposition of NiCrSiBC-60%WC ceramic coating on Inconel 718

Laser surface polishing of NiCrSiBC – 60WC ceramic-metal matrix composite deposited by laser directed energy deposition process

“…Prior to deposition, Inconel 718 substrates (50 mm × 25 mm × 8 mm) were grit blasted and cleaned in ultrasonic bath of ethanol. For substrate heating, a resistance heater controlled by variable auto-transformer was used [21]. An IR pyrometer (Micro Epsilon, model: CTLM-2HCF3-C3H) operating at 1.6 μm wavelength fitted with a 1064 ± 25 nm notch filter to block the reflected laser radiation was used to record the molten pool thermal history [21].…”

“…For substrate heating, a resistance heater controlled by variable auto-transformer was used [21]. An IR pyrometer (Micro Epsilon, model: CTLM-2HCF3-C3H) operating at 1.6 μm wavelength fitted with a 1064 ± 25 nm notch filter to block the reflected laser radiation was used to record the molten pool thermal history [21]. The pyrometer operates at 1 kHz frequency and acquires temperature signal from 0.7 mm diameter zone with measuring temperature range as ~785-3260 °C.…”

“…Also, the effect of polishing direction with respect to the initially deposited tracks is investigated. Unlike metal systems, ceramic-metal composite coatings suffer from surface cracks due to high residual stresses experienced from large variation in the thermo-physical properties of the metal matrix and ceramic particles when rapidly melted and solidified [20,21]. Thus the effect of substrate preheating on mitigation of cracks is also investigated.…”

Effects of Processing Parameters on Functionally Graded Materials for Industrial Components Repair

“…Preheat treatment is a solution to reduce residual stresses in FGMs, by reducing the cooling rate of both the substrate and the cladding [19,20], and attenuating the difference in thermal expansion coefficients between the several powders [21]. Thus, preheated substrates reduce the susceptibility to the formation of cracks, promoting better mechanical properties [22,25].…”

Deposition of Nickel-Based Superalloy Claddings on Low Alloy Structural Steel by Direct Laser Deposition

“…Preheating (PHT) is essential to control the cooling rate, minimising this effect. Increasing PHT temperature promotes the growth of the melt pool (depth and width), melting more substrate, thus increasing dilution [20][21][22][23][24]. PHT also prevents cladding delamination or cracking and reduces distortion and residual stresses due to the lower thermal gradient between the cladding and substrate [7,25,26].…”