CORRELATION BETWEEN MELT POOL TEMPERATURE AND CLAD FORMATION IN PULSED AND CONTINUOUS WAVE ND:YAG LASER CLADDING OF STELLITE

摘要

The melt pool temperature in pulsed laser cladding of stellite 6 was measured with a two-colour pyrometer. The pulse peak temperature (T{sub}p), durations when the melt pool temperature is above the melting points of stellite 6 powder (t{sub}1) and substrate (t{sub}2) in each pulse have been calculated and the effects of laser operating parameters (pulse energy, pulse frequency and spot overlap) on these values have been examined. It is found that T{sub}p only depends on the pulse energy and determines the melt pool size (D{sub}M), whereas the ratios of both t{sub}1 and t{sub}2 to the pulse length increase with pulse energy, pulse frequency (f) and spot overlap. The predictions of clad height, the total thickness of clad layer and dilution by T{sub}p, t{sub}1 and t{sub}2 are given for both pulsed and continuous wave (CW) laser cladding of stellite 6. Comparison between the experimental data and prediction has been made. Thick clad layer with low level of dilution requires higher value of the product of t{sub}1·f, longer beam interaction time (τ) and large D{sub}M.