| Using the surface modification technology to make metal matrix composite coatings with high wear resistance is an important way to extend the service life of components. In this research, the Fe-based coating reinforced by TiC, VC and Cr7C3 was fabricated by tungsten-insert gas (TIG) arc welding process employing a proper amount of alloy powder prepared on the surface of ordinary carbon steel substrate, and the microstructure, hardness, phase composition and wear properties of the coatings were researched systematically. At the same time, the factors and rules influencing the microstructure and properties were investigated. It is known that the alloy powder composition, pre-coating thickness, welding current, travel speed and number of deposition layers affect the formability of cladding layer and wear resistance. The deposition parameters were determined as follows:2% thorium tungsten electrode with diameter in 3,0mm;current of 140-160A; voltage of 15-20V; argon gas flow rate of 8L/min (the argon purity is 99.9%); based the powders' melting point as well as the accumulated experience of previous experiments. When doing the deposition test, the significant pool needs to be seen, but to avoid thermal deformation of the base material of metal. The microstructure, hardness and wear resistance of the various alloy powder coatings were investigated in this work.It is found that the powders constituents are the key factor to synthesize in-situ particulate reinforced iron-based cladding layer by using TIG welding process. All the claddings were well shaped and good bonding with the base metal, no pores, cracks and other defects.When only titanium-iron alloy and graphite powder were adopted, TiC particles with sharp corner were formed and dispersed in the cladding layer. Hardness of the cladding layer could reached to 52.4HRC.Due to the poor wetting of TiC to Fe matrix, it is difficult to fabricate multi-channel multi-layer cladding layers.Using chrome iron and graphite powder to prepare cladding layer. Selected two kinds of alloy powder ratio (high chromium and low chromium), and compare their microstructure we could see the obvious network organization. Starting from the substrate, cladding layer changed from the cellular-crystal to the central smaller equiaxed crystal.The high chrome cladding layer in which microstructure of more detailed, the Rockwell hardness value (54.1HRC) was bigger than the low chrome clad layer hardness (53HRC). The X-ray diffraction analysis of high chrome cladding layer showed that there is Cr7C3.Utilize the chrome-iron and titanium-iron compound added, the heat input could be effectively reduced and the possibility of deformation of the base metal will be reduced too. Ti element mainly sample microstructure photographs showed that the ferrite and pearlite with smaller spacing dispersed with massive, triangular shape and petal-shaped particles phase. Its average hardness could up to 54.3HRC. XRD results showed that there are TiC parcels which have edges and corners, but there is no Cr7C3.The Cr elements added low mainly had the role of solid solution strengthening in the Fe matrix.Cr element mainly cladding layer' microstructure showed that there were relatively smaller dispersed TiC particles and discontinuous network Cr7C3 organization. And its hardness of 52.1HRC was smaller.Used the orthogonal optimization of design principle to get the optimal ratio of titanium-iron, chrome iron, vanadium iron and graphite powder. Its microstructure photos showed there were bright white granular phase which shape was more rounded as well as the network organization. XRD analysis showed that there were TiC,Cr7C3 and VC phase in the matrix of ferrite and pearlite. Its surface hardness value was 56HRC, consistent with the theoretical value phase. From surface to the transition, the micro-hardness showed decreasing trends. Multi-channel multi-specimen hardness after deposition could up to 60HRC, which was more than twice the hardness of the base metal materials.Friction and wear test specimens were all made by multi-channel multi-layer method. The experimental results showed that the wear volume was decreasing trend with the wear and tear to extend the time. The wear trace on the coating analysis showed that the wear was mainly composited by micro-cutting, and the wear scar morphology showed features of abrasive wear. Titanium-iron and graphite powder coating with extended wear of time, deposition layer of TiC particles which had edges and corners off, forming different sizes of the pits, combined with abrasive right friction surface for micro-cutting, so wear scar specimen showed a small short and shallow furrows and scattered point pit. Well its wear resistance was worse. Furrows of the chrome iron and graphite (high-chromium) cladding layer were short and shallow, because the saturated net precipitation Cr7C3 combined with melting strengthening mechanisms of solid Cr could hinder the micro-cutting of abrasives to serve the strengthen. The SEM pattern of wear trace on the optimal alloy powder showed that a small amount of reinforcement particles exposed the surface. Then it had better wear resistance. In the titanium-iron + chromium iron + graphite powder sample, which had discontinuous network Cr7C3 and TiC with sharp corners, the wear track was mainly wide, shallow furrow, and no obvious pit after the formation of TiC particles falling off. And its wear resistance was between the in-between. The wear photo of the optimal alloy powder samples had a small amount of reinforcement particles exposure to the surface. Smooth particles TiC, VC reinforcement and non-continuous network of Cr7C3 hinder the process of friction, combined with Cr, V on strengthening the role of the matrix, so this sample showed smaller wear rate and best wear resistance.
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