| 304 stainless steel is a kind of common stainless steel materials, and one of the most widely used chrome-nickel stainless steel.As a kind of widely used steel,it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties, but it also has some faults of low hardness, poor wear resistance, passivation layer affecting the electrical conductivity, hydrogen embrittlement and corrosion clearance. And chromium nitride coating has a good hardness, wear resistance, corrosion resistant, high temperature oxidation resistance and other performance, at the same time it also has good heat and electricity conduction performance.It have very good mechanical and chemical surface protection, and Cr-N coating preparation of 304 stainless steel surface can effectively improve the wear resistance, corrosion resistance of 304 stainless steel. No matter as a friction piece or metal plate materials of proton exchange membrane fuel cell (PEMFC), it can help to improve the generality, practicability and economic behavior of 304 stainless steel.By r.f. magnetron reaction sputtering experimental method,I prepare polycrystalline Cr N coating in polished stainless steel substrate and nitride 304 stainless steel substrate.The coatings were characterized by SEM, XRD, micro vickers hardness tester, contact angle measurement instrument, and metallographic microscope. The influence of different substrates and process parameters (nitrogen flow) for coating wear resistance performance was studied by friction and wear tester.The influence of Cr2N coating for the corrosion resistance of nitriding 304 stainless steel was studied by electrochemical corrosion equipment Conclusions are as follows:(1)About the Cr-N coating preparation, with the increase of nitrogen flow,the grain structure transform from the triangular pyramid structure to cellular granular structure,reunion particle size on the surface of coating tends to decrease, Cr-N coating transforms from Cr and Cr2 N two phases to single phase Cr2N to CrN and Cr2N dual phase structure, when nitrogen flow rate continues to increase, it is composed of single-phase CrN.(2)About the wear resistance of Cr-N coating,in Ar28 N2, Ar25 N5 and Ar18N12 three atmosphere conditions, wear resistance of preparation coating on the nitriding 304 stainless steel is better than on polished stainless steel.In the nitrided stainless steel and Arl8N12 conditions for CrN coating, friction coefficient is 0.58.Compared to others,it has a certain extent improve, and wear scar is narrow.It has the best wear resistance.(3)About the Cr-N coating corrosion resistance, based on dynamic polarization corrosion potential test results, in the H2 and O2 environment, the sizes of corrosion resistance are Cr2N >304 stainless steel and 304 stainless steel> Cr2N. Static polarization corrosion test Static polarization corrosion test showed in the simulation of anode conditions shows that 304 stainless steel (Cr2N coating) has the lower polarization current density than 304 stainless steel, but increasing with time, current density is high, because the corrosion has began in micro holes.In the simulation of the cathode environment, because the passivation has occurred in the micro holes of stainless steel substrate, so it can provides high corrosion protection, negative effects in the coating of micro holes becomes small.304 stainless steel plate (Cr2N coating) and 304 stainless steel sheet show the similar corrosion current density values. In this experiment of Cr2N coating samples preparation, because of the better corrosion resistance,304 stainless steel plate (Cr2N coating) can replace stainless steel sheet as a bipolar plate materials. |
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