Study And Application Of Niobium-Nitrogen Cast Iron Cylinder Sleeve

This study shows that after adding niobium and nitrogen into the cast iron, Nb(C.iv) compound in the matrix structure appears and free nitrogen and oxygen are fixed. Besides, more clear grain boundary, increased amount of eutectic cell, and improved mechanical properties of the cast iron both in room and high temperature conditions are obtained. Due to the higher heat-resistance, melting point and microhardness of the Nb(C.N) compound, the antifusion-friction and abrasive wear resistance properties of the Nb-N sleeve are improved significantly and its service life is prolonged. The service life of Nb-N sleeve is aboout 40 percent longer than that of boron cast iron sleeve. By applying Nb-N sleeve, the overhaul mileage of gasoline engine used for medium load truck will be sore than 350 thousand kilometers. This means quite a benifit to endusers.

This study describes the tests of mechanical properties and abrasive wear behavior both in room and high temperature conditions under different Nb-N content, and the mechanism of wear resistance of Nb(C.N) compound. The strengthened bench tests amounting to three cycles of one thousand hours each cycle and road tests amounting to 800.000 kilometers on several medium toad trucks had been conducted for comparing Nb-N sleeve with others simultaneously before the conclusions were confirmed.