Wear Behavior of Modified Surface Layer Produced by TIG Melting of Preplaced Ti Powder in Nitrogen Environment

2014

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A comparison of a coating of Fe–Cr–B alloy powder processed on a plain carbon steel by surface melting using either laser or gas tungsten arc welding (GTAW) torch was made. The alloy powder was injected in laser melted surface, while the preplaced powder was melted using the GTAW technique. The topography of the GTAW tracks showed a relatively smooth surface, but the laser track surface was very rough. Because of high energy input, the GTAW method produced very wide and deep tracks with a high dilution compared to those of the laser tracks. Pores and fine cracks were seen in laser tracks; the cracks were elongated across the track width, and some of them propagated down to the melt depth. The GTAW track produced at a low energy was free from any cracking, but a centreline crack was present when processed at a high energy input.

“…Ripples were reported previously in both laser and GTAW processed composite coatings. 20,[22][23][24]…”

Section: Surface Topographymentioning

confidence: 99%

Section: Melt Geometrymentioning

confidence: 99%

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

Idriss

2014

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“…Following the publication of the initial research, [16][17][18][19] an increasing number of papers based on the present work have been reported in the literature. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] However, there are few reports of investigations that produce significant relationships between the processing conditions and the coating quality, especially on steel substrates. A recent experimental study by Mridha et al 32 incorporated TiC particulates into an AISI 4340 low alloy steel surface, using a powder preplacement technique and melting under a TIG torch to give a single track.…”

Section: Introductionmentioning

confidence: 99%

Overlapping tracks processed by TIG melting TiC preplaced powder on low alloy steel surfaces

2015

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An overlapping composite track coating was produced on a steel surface by preplacing an 0.5 mm thick layer of TiC powder and then melting using a TIG torch of constant energy input. The influence of the overlapping operation on preheating of the substrate, the dissolution of TiC particulates and the subsequent depth and hardness of the composite layer was analysed. The melt microstructure consisted of both undissolved and partially dissolved TiC particulates, together with a variety of morphologies and sizes of TiC particles precipitated during solidification. Preheating, resulting from the overlapping operation occurred, producing additional melting of the TiC particulates and deeper melt depths but with a reduced volume fraction of TiC precipitates in the subsequent tracks. A maximum hardness of over 800 Hv was developed in the composite layer. The high hardness was unevenly distributed in tracks melted at the initial and final stages, while it varied across the melt depths in other tracks.

“…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.…”

mentioning

confidence: 99%

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

Idriss

2015

Self Cite

A comparison has been made of the relationship between microstructure and microhardness developed by surface melting Nanosteel SHS 7170 Fe-Cr-B alloy powder onto a plain carbon steel surface. This powder was initially developed as a high velocity oxy fuel sprayed coating giving a strength ten times that of mild steel, and is particularly suitable for surface protection against wear and corrosion. In this study, the alloy powder was injected into the laser melted surface, while a preplaced powder was melted using the gas tungsten arc welding (GTAW) technique. The laser track consisted of fine dendrites and needle-like microstructures which produced a maximum hardness value of over 800 HV, while the GTAW track produced a mixture of equiaxed and columnar grain microstructures with a maximum hardness value of 2 670 HV. The lower hardness values are considered to be associated with dilution and grain size.