Scratch Resistance and Damage Mechanisms Arising in Titanium Carbide–Nickel Aluminide-Based Laser DED Clads on D2 Tool Steel

TiC-based cermet clads were applied onto high-Cr-containing, cold work D2 tool steel substrates through laser-directed energy deposition (L-DED). A novel suspension-based preplacement method was used to apply the feedstock prior to laser cladding. The preplaced material was then subjected to laser processing using various laser powers (200 to 350 W) and scanning speeds (58 to 116 mm/min.), resulting in the fabrication of high-density clads on the substrates. Hardness profiles were generated by cross-sectional micro-indentation of the clad layers. Micro-Vickers hardness (HV) values of the cermet clads were measured from load–displacement curves under a range of applied normal forces, which are in the range of 265.7 to 890.3 HV. As a preliminary assessment of the wear response, a variety of single-pass scratch testing approaches were undertaken. A qualitative evaluation of ‘interface’ mechanics between the ‘clad’ and substrate material was also performed by cross-sectional scratching of the clads; as a chemical clad is developed, this effectively is assessing the transitions through the clad microstructure. Failure modes and damage mechanism were examined at different processing parameters by means of acoustic emission (AE) and coefficient of friction (COF) measurements, together with assessment of the post-test microstructures. The scratch hardness (HSp) of the cermet clads varied within the range of 4.88 to 7.58 GPa, as a function of applied normal force (ranged within 10–40 N), which was considerably higher than the D2 substrate (HSp = 3 GPa).