In this paper, in situ synthesized TiC particles reinforced Fe-based surface composite coatings by multi-pass overlapping gas tungsten arc welding (GTAW) melting process employing a proper amount of graphite and ferrotitanium (FeTi) on AISI 1020 steel substrate was produced. The microstructure and wear properties of the composite coatings were investigated by means of an electron microprobe microanalysis (EPMA), X-ray diffractometer and wear tester. The results showed that the multi-pass overlapping GTAW melting surface composite coatings can be obtained under suitable welding parameters, and no crack and porosity are found in the tracks. The X-ray and EPMA results confirm that TiC particles can be formed via reaction of FeTi and graphite during multi-pass overlapping GTAW melting process. TiC particles present cubic and dendrite shape in the non-overlapping zone. It is found that there occurred TiC particles coarsening at the overlap regions, which can lead to detrimental effects on the hardness and wear performance. Composite coatings give a high hardness and excellent wear resistance; and the wear friction coefficient of the coating is less than that of the 1020 steel. As a result, multi-pass overlapping GTAW melting process can be used effectively for producing surface composite coatings with a pre-placed powder to improve wear resistance of the AISI 1020 steel.

Characterization of in situ synthesized TiC particle reinforced Fe-based composite coatings produced by multi-pass overlapping GTAW melting process

In the present study, AISI 1045 steel surfaces were alloyed with pre-placed graphite, ferrotitanium and Fe–Cr–B–Si powders by using a tungsten-inert gas (TIG) heat source. The effects of welding parameters and thickness of the pre-placed powder layers on the microstructure and properties of the coatings were also investigated. The results indicated that TiC particles can be obtained by direct metallurgical reaction between ferrotitanium and graphite during the TIG welding process. Most of TiC particles were uniformly distributed in the surface coating. The microhardness showed a gradient variation from the molten boundary to the top surface of the coatings, and it was influenced by the thickness of the pre-placed powder layer and the welding parameters. The surface composite coating exhibited a higher hardness and lower wear rate than that of the substrate due to the formation of TiC carbides.

In situ production of Fe–TiC surface composite coatings by tungsten-inert gas heat source

In this study, the effect of cooling rate after heat treatment on mechanical properties, fatigue life, precipitation and fracture mode of an austenitic Mn Hadfield steel was investigated Cast samples of the Hadfield steel were heat treated at 1100  C for 2 h The samples were subsequently quenched in pure water and also in 3 wt% NaCl salt bath Optical microscope (OM) and scanning electron microscope (SEM) were used to analyze microstructure and fracture surfaces Transmission electron microscope (TEM) was used to assess the precipitates X-ray diffraction (XRD) was used to determine the phases formed Mechanical properties and fatigue life were determined by uniaxial tensile test, bending fatigue and hardness measurements Results showed that the sample quenched in salt bath had lower Mn3C precipitates, hardness, yield and tensile strengths Instead, this situation resulted in a more ductile fracture mode and higher formability Finally, the fatigue life of the sample quenched in salt bath was longer than the one quenched in pure water

The Effect of Heat Treatment Process Parameters on Mechanical Properties, Precipitation, Fatigue Life, and Fracture Mode of an Austenitic Mn Hadfield Steel

Corrosion behavior of TiC particle-reinforced 304 stainless steel

The objective of this work is to investigate the correlation of microstructure with wear resistance in a hardfacing material reinforced with Fe-(TiW)C composite powder particles. This material was designed for cladding components subjected to highly abrasive conditions and was deposited on a low-carbon steel substrate by open arc welding. The theoretical and experimental work undertaken includes solidification study, microstructural characterization, and abrasive wear testing. Microstructural analysis of the hardfaced top layer of the alloy showed the presence of TiWC carbide particles and TiNbC carbides randomly distributed in a eutectic mixture matrix γ/M7C3 containing primary austenite dendrites. Microstructural examinations also showed that hard and fine spherulitic carbides, in which a Ti-rich MC carbide core was encircled by MC carbide enriched with Nb and W, were homogeneously distributed in the matrix. The energy-dispersive spectroscopy (EDS) mapping of spherulitic carbides showed that the any added Nb replaced a significant part of W in the Fe-(TiW)C powder, and W preferentially partitioned into other carbides and matrix during solidification. Abrasion test results showed that the preceding carbides improve the wear resistance of the hardfacing material in comparison with conventional Fe-Cr-C and Fe-Cr-C-Nb alloys, especially under high stress conditions.

Y. L. Ren

Papers

In-situ formation of TiC/Hadfield steel composites