Effect of Corrosion Environment on the Fatigue Behavior of WC — Co Hard Alloy Teeth of Drill Bits

The fatigue crack growth in WC-Co hard alloys with cobalt content from 6 to 12 wt pct has been investigated in air and fluids of pH from 4.5 to 10.5. Significant difference in crack growth rates at low the stress intensity factor range was detected. It was established that the negative influence of corrosion environment on fatigue crack growth resistance of WC-Co hard alloy increases significantly for compositions with higher cobalt content. This effect is observed in fluids of various pH-values. Lower operating life of hard alloy inserts of drill bits in service environment corresponds to hydrogen embrittlement of cobalt phase.