等离子喷涂NiCrBSi涂层接触疲劳过程中残余应力变化规律研究

采用超声速等离子喷涂技术在45钢基体上制备NiCrBSi合金涂层,涂层整体结构致密,含有少量微缺陷。使用球盘式接触疲劳试验机在接触应力为1.86 GPa,转速为1 500 r/min的条件下对涂层试样进行接触疲劳试验,得到涂层的接触疲劳寿命为9.0×105周次;同时建立Weibull失效概率图,通过该图可以直观地得到在同一工作条件下,涂层任意循环次数的失效概率。测量涂层不同疲劳阶段的残余应力,结果表明:一旦进行接触疲劳试验,其残余应力形式由拉应力迅速转化为压应力,在整个疲劳过程的前半段,应力增强较为缓慢,在疲劳过程的后半段,应力值迅速增大,疲劳过程的中期成为了应力变化的转折点。根据这一规律,可以有效地判定涂层处于疲劳过程的哪个阶段,从而为预防涂层的突然失效提供了一种新的手段。

Study on the Residual Stress of Plasma Sprayed NiCrBSi Coating in Contact Fatigue Process

The NiCrBSi alloy coating is deposited on steel(AISI 1045) substrates using supersonic plasma spraying technique.The overall structure of the coating is densification and contained a small amount of micro-defects.Rolling contact fatigue(RCF) life of the coating is investigated using a ball-on-disc tester under 1.86 GPa contact stress,and 1 500 r/min rotation velocity.Obtained that the contact fatigue lifetime of coating is 9.0×105 cycle,map of Weibull distribution failure probability is plotted as well.And the failure probability of random cycle is achieved by this Weibull plot under identical work condition.Coating’s residual stress at stage of fatigue life is measured by the X-ray equipment.The results show that the residual stress changed by tensile stress into compressive stress when contact fatigue tests start,and the stress rises slowly in the first half of fatigue process while increases sharply in the following procedure,which makes the mid-stage became the critical point of fatigue failure process.Following this law,fatigue stage of coating can be determined,and the catastrophic failure of coating can be prevented effectively.