電(dian)(dian)子(zi)(zi)束(shu)(shu)(shu)表(biao)面強(qiang)化(hua)是利用(yong)高能量密(mi)度的(de)(de)電(dian)(dian)子(zi)(zi)束(shu)(shu)(shu)加熱(re)(re)進行(xing)表(biao)面淬(cui)火的(de)(de)新技術。電(dian)(dian)子(zi)(zi)束(shu)(shu)(shu)加熱(re)(re)可(ke)(ke)以達(da)到106~108W/c㎡的(de)(de)能量密(mi)度。圖3-18所(suo)示(shi)為(wei)電(dian)(dian)子(zi)(zi)束(shu)(shu)(shu)表(biao)面加熱(re)(re)淬(cui)火裝置示(shi)意圖。利用(yong)電(dian)(dian)子(zi)(zi)束(shu)(shu)(shu)亦可(ke)(ke)實現相變(bian)硬化(hua)、熔(rong)化(hua)、凝固和表(biao)面合金化(hua)。電(dian)(dian)子(zi)(zi)束(shu)(shu)(shu)是由陰極(燈絲(si))發出的(de)(de)電(dian)(dian)子(zi)(zi),通過高電(dian)(dian)壓環形陽極加速,并(bing)聚焦成束(shu)(shu)(shu)使電(dian)(dian)子(zi)(zi)束(shu)(shu)(shu)流打(da)擊(ji)金屬表(biao)面,達(da)到加熱(re)(re)的(de)(de)效果。
由于高(gao)能量(liang)(liang)密(mi)度的電子束(shu)是在極短(duan)的時(shi)間內打擊金屬表(biao)面(mian)(mian)(mian),所以使(shi)熱量(liang)(liang)在表(biao)面(mian)(mian)(mian)逸(yi)散的表(biao)面(mian)(mian)(mian)溫度,就可(ke)以達到相變溫度范圍。當被加熱表(biao)面(mian)(mian)(mian)吸收(shou)的熱量(liang)(liang)很快地被底層(ceng)材(cai)料吸收(shou)而冷卻時(shi),就可(ke)以完成淬火冷卻過程,從(cong)而產生有(you)效的自行淬火。
和(he)激光(guang)熱(re)(re)處理相(xiang)(xiang)比(bi),電(dian)(dian)子(zi)束(shu)(shu)熱(re)(re)處理的(de)缺點是模具必須放在真空室內(nei),裝(zhuang)卸(xie)不方(fang)便(bian)。但是電(dian)(dian)子(zi)束(shu)(shu)熱(re)(re)處理的(de)加熱(re)(re)效率比(bi)激光(guang)高,不需要(yao)激光(guang)熱(re)(re)處理的(de)“表(biao)面黑化”過程。凡激光(guang)能對(dui)準的(de)表(biao)面都可(ke)以(yi)利用電(dian)(dian)子(zi)束(shu)(shu)加熱(re)(re),電(dian)(dian)子(zi)束(shu)(shu)的(de)快速加熱(re)(re),使(shi)零(ling)件變形(xing)極小,無需后續的(de)校正工作,淬(cui)火后的(de)金(jin)相(xiang)(xiang)組織可(ke)獲得細晶結構。表(biao)3-42所列(lie)為42CrMo鋼電(dian)(dian)子(zi)束(shu)(shu)表(biao)面淬(cui)火的(de)效果。