按照氫脆敏感性與應變速率的關系，可以將氫致開裂分為兩大類。

1. 第一類(lei)氫脆

 氫脆的敏感性隨應變速率的增加而增加，即材料加載前內部已存在某種裂紋源，加載后在應力作用下加快了裂紋的形成與擴展。第一類氫脆包括三種形式：①. 氫腐蝕，由于氫在高溫高壓下與金屬中第二相（夾雜物和合金添加物）發生化學反應，生成高壓氣體（如CH₄、SiH₄)引起材料脫碳、內裂紋和鼓泡的現象；②. 氫鼓泡，過飽和的氫原子在缺陷位置（如夾雜）析出，形成氫分子，在局部造成很高的氫壓，引起表面鼓泡或內部裂紋的現象；③. 氫化物型氫脆，氫與IVB和VB族金屬有較大的親和力，氫含量較高時容易產生脆性的氫化物相，并在隨后受力時成為裂紋源，引起脆斷。

 上(shang)述三種情況將造成金屬(shu)永久損(sun)傷，使材料塑性(xing)或(huo)強(qiang)度降低，即使從金屬(shu)中(zhong)除(chu)(chu)氫損(sun)傷也不(bu)能消除(chu)(chu)，塑性(xing)或(huo)強(qiang)度也不(bu)能恢(hui)復，故稱為不(bu)可逆(ni)氫脆。

2. 第二類氫脆

 氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)的(de)(de)(de)(de)(de)敏(min)感(gan)性(xing)(xing)(xing)(xing)隨應變(bian)速(su)率增加而(er)降低(di)，即(ji)(ji)材料在(zai)(zai)加載前并不存在(zai)(zai)裂(lie)紋源，加載后(hou)在(zai)(zai)應力(li)和氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)的(de)(de)(de)(de)(de)交互作用下(xia)逐(zhu)漸形(xing)(xing)(xing)成(cheng)(cheng)(cheng)裂(lie)紋源，最(zui)終(zhong)導(dao)致(zhi)(zhi)脆(cui)(cui)(cui)性(xing)(xing)(xing)(xing)斷裂(lie)。第二類氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)包括兩(liang)種形(xing)(xing)(xing)式：一是(shi)應力(li)誘發(fa)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)化(hua)物型氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)。在(zai)(zai)能(neng)夠形(xing)(xing)(xing)成(cheng)(cheng)(cheng)脆(cui)(cui)(cui)性(xing)(xing)(xing)(xing)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)化(hua)物的(de)(de)(de)(de)(de)金屬(shu)中(zhong)，當(dang)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)含量較(jiao)低(di)或(huo)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)在(zai)(zai)固溶(rong)體(ti)中(zhong)的(de)(de)(de)(de)(de)過飽和度較(jiao)低(di)時，尚不能(neng)自(zi)發(fa)形(xing)(xing)(xing)成(cheng)(cheng)(cheng)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)化(hua)物；而(er)在(zai)(zai)應力(li)作用下(xia)，氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)會向(xiang)應力(li)集中(zhong)處富(fu)集，當(dang)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)濃(nong)度超(chao)過臨(lin)界值(zhi)時就會沉淀出(chu)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)化(hua)物。這種應力(li)誘發(fa)的(de)(de)(de)(de)(de)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)化(hua)物相變(bian)只(zhi)在(zai)(zai)較(jiao)低(di)的(de)(de)(de)(de)(de)應變(bian)速(su)率下(xia)出(chu)現(xian)(xian)，并由此(ci)導(dao)致(zhi)(zhi)脆(cui)(cui)(cui)性(xing)(xing)(xing)(xing)斷裂(lie)，一旦出(chu)現(xian)(xian)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)化(hua)物，即(ji)(ji)使(shi)卸載除(chu)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)，靜止一段(duan)時間后(hou)再高速(su)變(bian)形(xing)(xing)(xing)，塑性(xing)(xing)(xing)(xing)也(ye)不能(neng)恢復，故也(ye)是(shi)不可(ke)逆(ni)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)。二是(shi)可(ke)逆(ni)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)。是(shi)指含氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)金屬(shu)在(zai)(zai)高速(su)變(bian)形(xing)(xing)(xing)時并不顯(xian)示脆(cui)(cui)(cui)性(xing)(xing)(xing)(xing)，而(er)在(zai)(zai)緩慢變(bian)形(xing)(xing)(xing)時由于氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)逐(zhu)漸向(xiang)應力(li)集中(zhong)處富(fu)集，在(zai)(zai)應力(li)與氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)交互作用下(xia)裂(lie)紋形(xing)(xing)(xing)核、擴展，最(zui)終(zhong)導(dao)致(zhi)(zhi)脆(cui)(cui)(cui)性(xing)(xing)(xing)(xing)的(de)(de)(de)(de)(de)斷裂(lie)，在(zai)(zai)未形(xing)(xing)(xing)成(cheng)(cheng)(cheng)裂(lie)紋前去(qu)除(chu)載荷(he)，靜置(zhi)一段(duan)時間后(hou)高速(su)變(bian)形(xing)(xing)(xing)，材料的(de)(de)(de)(de)(de)塑性(xing)(xing)(xing)(xing)可(ke)以得到恢復，即(ji)(ji)應力(li)去(qu)除(chu)后(hou)脆(cui)(cui)(cui)性(xing)(xing)(xing)(xing)消失，因此(ci)稱(cheng)為可(ke)逆(ni)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)。由內氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)引(yin)起(qi)的(de)(de)(de)(de)(de)稱(cheng)可(ke)逆(ni)內氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)，由外氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)引(yin)起(qi)的(de)(de)(de)(de)(de)稱(cheng)環境氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)。通常所說(shuo)的(de)(de)(de)(de)(de)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)主(zhu)要指可(ke)逆(ni)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)脆(cui)(cui)(cui)，是(shi)氫(qing)(qing)(qing)(qing)(qing)(qing)(qing)(qing)致(zhi)(zhi)開(kai)裂(lie)中(zhong)最(zui)主(zhu)要、最(zui)危險的(de)(de)(de)(de)(de)破壞形(xing)(xing)(xing)式。