润滑油中微细碳粉颗粒对45^#钢接触疲劳寿命影响的研究

Effect of the Carbon Powder in Lubricating Oil on Contact Fatigue Life of 45# Steel

在20^#机械油中添加适量的微期碳粉硬质颗粒可以提高45^#钢（调质处理，HB=300)的接触疲劳寿命。含碳粉油样的调配此例(wt)有两种，即碳粉：分散剂：纯20^#机械油=1：1：100和2：1：100。研究结果表明，在给定的试验条件下，45^#钢于这两种油样中的接触疲劳寿命分别由纯20^#机械油中的2．6倍和5．0倍。作者还就碳粉的作用机理进行了考察，指出添加碳粉之所以能够提高试件的接触疲劳寿命，原因在于它使润滑油的粘度增大及其渗入到疲劳裂纹中减缓了裂纹的扩展。

The comparative test of the contact fatigue life of 45# steel was performed with four lubricating oil samples whose mixture ratio are shown in Table 1. Table 1 The mixture ratio of four lubricating oil Samplex Mixture ratio (wt) A pure 20# machinery oil B dispersing agent : 20# machinery oil = 1: 100 C carbon powder : dispersing agent : 20# machinery oil=1: 1 : 100 D carbon powder : dispersing agent : 20# machinery oil = 2 : 1 :100 The results shown that under using C and D samples with carbon powder the contact fatigue life of 45# steel is 2.6 and 5.0 times than that of using A sample respectively. In addition, the mechanism of carbon powder was also investigated in this paper. The reason of increasing contact fatigue life by adding carbon powder are as follows: a. The viscosity of the lubricating oil samples increases with pressure increasing. The higher the carbon powder content, the quicker the increasing of rate. The pressure on contact point between test bar and ball can reach 2000MPa. The viscosity of samples with carbon powder is higher than that of samples without it. The thickness of oil film increases, therefore, contact fatigue life of testing piece prolongs. b. When the fatigue crack is formed on the contact surface the carbon powder in the sample can be infased into the crack, because of hard carbon particles the opening of crack can not be blocked although the steel ball roll it, so the high pressure in the crack can not be formed. Adding the carbon powder into lubricating oil can decrease the extending rate of crack and prolong the contact fatigue life of testing piece.