| Surface treatment technology has achieved significant progress in improving the quality of products and mould life which has huge economic benefits. The full application of surface treatment technology is an important economic and efficient means to improve the mould life. Welding used of plasma arc in an ordinary high-performance alloy surface layer as one of the material of surface hardening technology, Alloys with less material consumption, to spray a variety of alloy powder materials, can be watered down the rate of low-dense layer of the spray, low cost, high production efficiency, easy automation and owe many other advantages. Thus it is used in machinery, metallurgy, electric power, railway applications fields more and more widely which has acquired significant economic benefits. At the present time, Plasma arc welding has been successfully used in repairing molds, in internal combustion engines, valves manufacturing etc. sector has also been widely used, Petro-chemical industry also carry out key parts for surface modification. Plasma arc welding of metal has combined strength and toughness and good metallurgical process layer and the surface of high hardness, good chemical stability with high wear resistance, which constitutes a new kind of composite material. Thus it has greatly improved the performance of materials. Making it be used for easy wear parts of mould can substantially extend service lifetime, at the same time reduce the financial review of the application of laser technology brought about by the high cost, which have broad application prospects.In this paper, according a large number of experimental analysis of iron-based alloy PTAW, we have researched microstructure, hardness and wear resistance of the spraying welding layer an in-depth, the main conclusions are given as follows:1. With the content of high-carbon ferrochrome appended in FFe55 increased gradually, the content of carbon and chromium in spraying welding layer increased gradually, the transformation of microstructure is Hypoeutectic- Eutectic- Hypereutectic. With the content of FFe1160 appended in FFe55 increased gradually, the content of carbon, chromium and nickel increased, the transformation of microstructure is Hypoeutectic- Eutectic- Hypereutectic. 2. When the microstructure of spraying welding layer is Hypoeutectic, the wear resistance is poor; the spraying welding layer of Eutectic is improved to some extent; when the microstructure of spraying welding layer is Hypereutectic owing primary carbide whose magnitude is appropriate and dispersion is symmetrical, the wear resistance is the best; when the number of primary carbide in spraying welding layer is too much, the wear resistance begin to descend. When the spraying layer in the content of carbon 1.96%, chromium 24.25%, boron 0.42%, minimum wear weight lossΔW is 11.2mg, wear resistance is the best of all, the relative wear resistance is 3.5 times than the one of the market spray welding alloy powder FFe55.3. When HRC<60, the relative wear resistance of spraying welding layer has assumed increasing trend with hardness increased. When HRC>60, there are not clear law between the relative wear resistance and hardness of spraying welding layer. The hardness of material is not the exact indicator of measuring wear resistance.4. The quality of wear resistance of materials mainly depends on the total amount of hard carbides and their morphology, dispersion, the nature of matrix and how to match with matrix A certain number of hard tissues existed in spraying welding alloy is only a necessary condition for high abrasion resistance; At the same time, spraying welding layer has enough strength, hardness and tenacity of the matrix structure in order to own strong support, which is to ensure that spraying welding layers have a sufficient condition for high wear resistance.5. Through microscopic analysis, the defects emerged in plasma spraying welding layer are pores, cracks and non-fusion. Mainly by improving the surface quality of substrate, optimizing the technics criterion and the alloy system can we avoid the defects.
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