ENVIRONMENTAL EFFECTS ON FRETTING WEAR

本文研究了锆合金在空气、蒸馏水和Na_2SO_4溶液中的微动磨损性能。核电计划反应堆的燃料棒采用的是锆合金。此外，我们还对腐蚀磨损机理进行了研究，以了解腐蚀环境下的微动磨损机理。该装置在空气和蒸馏水中的临界滑移幅度为100μm。随着载荷的增加，磨损量增加。在往复滑动磨损试验机上考察的腐蚀磨损参数为：溶液浓度从10~(-1)~10~(-5)~10~(-5)~10~(-5)~10~(-5)~10~(-5)~10~(-5)~10~(-1)。腐蚀磨损由机械磨损和电化学磨损组成，在纯水中发生机械磨损。在Na_2SO_4溶液中的腐蚀磨损中，浓度对磨损量的影响出现在10^~(-3)~(-3)mol/L以上，且随着电位的升高而增大。考察了载荷和面积比对磨损量和自由电位降的影响。载荷的增加会导致磨损量和电势降的增加。这是由于暴露在新鲜表面的增加造成的。根据总磨损量与纯水中的磨损量之差，得出了电化学因素对磨损量的贡献。在这种情况下，这一比例约为15%。电位的增加意味着，由于阳极电流密度的降低，对磨损(金属的溶解)的电化学效应降低。由于微动磨损的磨痕较小，且面积比很小，其电化学贡献较大，需要进一步研究以获得核反应堆等高温、高环境压力下的数据。

In this work, we examined the fretting wear properties of Zr-alloy under dry in air, in distilled water and in Na_2SO_4solution. Zr-alloy is used as fuel rods in the reactor of nuclear power plan. Furthermore, we examined the corrosive wear mechanism to understand the mechanism of fretting wear in corrosive environment. The critical slip amplitude of the fretting was 100 μm in air and in distilled water for the apparatus of Kyungpook University. As load increased, wear increased. But wear decreased with increasing load in distilled water, which was caused by the change in slip regime from gross slip to partial slip.In corrosive wear, which was examined using the reciprocating sliding wear apparatus, the parameters were solution concentration from lO^<-1> mol/l to 10^<-5> mo1/1, potential, load and anode area / cathode area ratio. As corrosive wear consisted of mechanical wear and electrochemical wear, mechanical wear was obtained in pure water. In the corrosive wear in Na_2SO_4 solution, the effect of concentration on wear volume appeared above 10^<-3> mol/l, and it increases with potential. The effects of load and area ration on wear and free potential drop were examined. The increase in load results in the increases in wear and potential drop. This is caused by the increase in fresh surface exposed. The contribution of electrochemical factor was obtained from the difference between total wear volume and wear volume in pure water. It was about 15 % in this case. The increase in potential meant that the electrochemical effect on wear (dissolution of metal) was reduced because of the decrease in anodic current density. Wear decrease with increasing the area ratio due to the increase in the potential drop.As the fretting wear has small wear scar, and the very low area ratio, the electrochemical contribution would increase.More investigation is needed for getting the data at high temperature and high ambient pressure like nuclear power reactor.