Incorporation of TiC Particulates on AISI 4340 Low Alloy Steel Surfaces via Tungsten Inert Gas Arc Melting

Abstract

Surface cladding utilizes a high energy input to deposit a layer on substrate surfaces providing protection against wear and corrosion. In this work, TiC particulates were incorporated by meltingsingle tracksin powder preplaced onto AISI 4340 low alloy steel surfaces using a Tungsten Inert Gas (TIG) torch with a range of processing conditions. The effects of energy input and powder content on the melt geometry, microstructure and hardness were investigated. The highest energy input (1680 J/mm) under theTIG torchproduced deeper (1.0 mm) and wider melt pools, associated with increased dilution, compared to that processed at the lowest energy (1008 J/mm). The melt microstructure contained partially meltedTiC particulatesassociated with dendritic, cubic and globular typecarbidesprecipitated upon solidification of TiC dissolved in the melt; TiC accumulated more near to the melt-matrix interface and at the track edges. Addition of 0.4, 0.5 and 1.0 mg/mm2TiC gave hardness values in the resolidified melt pools between 750 to over 1100Hv, against a base hardness of 300 Hv; hardness values are higher in tracks processed with a greater TiC addition and reduced energy input.

Melting of multipass surface tracks in steel incorporating titanium carbide powders

“…This is an action which increases the rate of dissolution of reinforcing material, together with that the substrate. 25 The low energy region at the bottom of the melt pool, adjacent to the base metal, where the pool was only just above the melting temperature of steel, was insufficient to melt the surging particulates, resulting in agglomeration, as seen in Fig. 6a.…”

“…Details of the powder preplacement method were described previously. 11,25 Multipass tracks, with 50% overlapping between tracks, were melted on the TiC preplaced surface using a TIG welding torch generated by applying a current of 80 A at 35 V. The specimen stage had a traversing speed of , where V is voltage, I is current, S is scanning speed and is the efficiency of heat absorption, which is given as 48% for TIG torch melting. 28 Analytical models for calculating are given in, for examples, References 29 and 30 .…”

“…Using a TIG energy input of 1344 J mm -1 , MMC layers having a good metallurgical bond and free from cracks and porosity were obtained. 25 The microstructure consisted of TiC dendrites associated with unmelted and partially melted TiC particulates dispersed in the melt pool.…”

“…27 TiC has received some attention as a reinforcing material on the substrate surface to increase resistance against wear. 25 In parallel research with overlapped tracks, the TIG process was used to melt TiC powder on an AISI 1050 mild steel substrate. This achieved an approximately constant microhardness value of 800 HV in the first track, from the surface to the depth at 2.2 mm.…”

Laser and GTAW torch processing of Fe–Cr–B coatings on steel

“…The melt cross-sections of both laser processed tracks and GTAW tracks were hemispherical in shape, as described in part I 20 , and have also been observed previously. [24][25][26][27] The variation in geometric dilution was reflected in the development of the microstructure, composition and hardness in the coatings produced by the two surface melting techniques.…”