300M钢超音速火焰喷涂WC/17Co涂层的疲劳性能

Fatigue Property of HVAF Sprayed WC/17Co Coating on 300M Steel

夹杂物尺寸对超高强结构钢的疲劳寿命有明显影响。疲劳断口分析表明,300M超高强钢中的疲劳裂纹源主要由其中的夹杂物所造成。而超音速火焰喷涂WC/17Co处理后300M钢裂纹源全部来自于基体中的夹杂,夹杂组成均为Al2O3.xCaO.ySiO2。分别采用统计极值法和广义Pareto分布对不同质量300M钢中的最大夹杂物进行估计,与实际疲劳断裂的最大夹杂物尺寸进行对比,并对不同质量300M钢的疲劳极限进行估算。HVAF处理使300M钢中次表面的残余压应力增大,对抑制裂纹萌生和扩展有利。试验结果表明,在低载荷下HVAF提高了基体疲劳寿命,而在高载荷下由于压应力作用有限,以及喷砂氧化铝对300M钢表面造成损伤带来负面作用而降低300M钢的疲劳寿命。

Inclusion size in the steel produced significant influence on the fatigue performance of ultra-high strength steel. Fatigue fractograph revealed that the crack was mainly initiated at the inclusion for bare 300M steel and was completely initiated at the inclusion in the substrate for HVAF sprayed WC/17Co coating in 300M steel. The crack was composed of Al2O3. xCaO. ySiO2. Therefore, statistic extreme values and generalized Pareto distribution were used to estimate the maximum inclusion sizes for different mass of 300M steel in comparison with the experimental result. The fatigue limit was predicted according to the estimated maximum inclusion size in the different mass of 300M steel. HVAF treatment led to the higher residual compressive stress in the subsurface of substrate, which was ben- eficial to the inhibition of crack initiation and propagation. The results showed that the fatigue lives of 300M steel were increased after HVAF treatment at the low stress level, however, decreased slightly due to the limited effect of compressive stress and negative effect of grit blasting at the high stress level.