(北京航空材料研究院 先進(jìn)高溫結(jié)構(gòu)材料國防科技重點(diǎn)實(shí)驗(yàn)室，北京 100095)
摘 要: 真空感應(yīng)熔煉高Cr鑄造Ni基高溫合金K4648，重熔澆注成等軸晶成形試棒。對薄截面試棒和厚截面中柱管澆道進(jìn)行(1 180 ℃, 4 h)固溶處理和(1 180 ℃, 4 h)+(900 ℃, 16 h)標(biāo)準(zhǔn)熱處理。鑄態(tài)和熱處理態(tài)試樣通過光學(xué)金相、定量金相、掃描電鏡及能譜分析和X射線衍射分析確定合金中相的種類、形貌和成分。結(jié)果表明：K4648合金鑄態(tài)組織中主要存在γ基體、初生α相和MC碳化物；初生α相是Ni、Mo和W在Cr中的過飽和固溶體，其中Ni含量(摩爾分?jǐn)?shù))可達(dá)30%以上，本研究中的α相可命名為α-(Cr, Ni)；在0.2 N載荷下，該α相的維氏顯微硬度值為6.3 GPa，是一種硬而脆的相；經(jīng)(1 180 ℃, 4 h)固溶處理，初生α相和MC碳化物都會(huì)回溶，并且轉(zhuǎn)變?yōu)镸23C6碳化物，M23C6碳化物比初生α相具有更高的Cr含量和更低的Ni含量。固溶處理后特別是在厚截面試樣中還殘存未轉(zhuǎn)變的α相和MC碳化物。(1 180 ℃, 4 h)+(900 ℃, 16 h)標(biāo)準(zhǔn)熱處理后，合金內(nèi)部廣泛析出片狀次生α相和γ′-Ni3(Al, Ti ,Nb)相，且在晶界區(qū)補(bǔ)充析出粒狀M23C6碳化物，起到強(qiáng)化合金的作用。
關(guān)鍵字: 鎳基高溫合金；K4648；α-(Cr, Ni)相；M23C6碳化物；顯微組織
（National Key Laboratory of Advanced High Temperature Structural Materials,
Beijing Institute of Aeronautical Materials, Beijing 100095, China）
Abstract: High Cr content cast Ni-base superalloy K4648 was prepared by vacuum induction melting (VIM). The ingot was remelted and poured into the investment mold to make shape equiaxed test bars. The solid solution treatment of (1 180 ℃, 4 h, A.C.) and standard heat treatment of (1 180 ℃, 4 h, A.C.)+(900 ℃, 16 h, A.C.) were carried out on both the small size section shaped test bars and large size section runner riser. The as-cast and heat-treated specimens with different section sizes were analyzed by optical metallograhpy (OM), quantitative metallography (QM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometry (XRD) to determine the type, morphology, and composition of phases in K4648 alloy. The results indicate that the primary phases in K4648 alloy are mainly γ matrix, α phase and MC carbide. The primary α phase is an oversaturated solid solution of (Ni+Mo+W) in Cr. The concentration (molar fraction) of element Ni can reach above 30%, thereby primary α phase in this study can be nominated as α-(Cr, Ni). At the load of 0.2 N, α-(Cr, Ni) possesses a Vickers microhardness of 6.3 GPa, which is a brittle and hard phase. The heavy section castings exhibit larger size and amount of primary α phase, which is a kind of harmful phase and needs to be controlled. The primary α phase and MC carbides will solid-solution and transform to M23C6 carbide after (1 180 ℃, 4 h) treatment. The M23C6 carbide possesses higher Cr content and lower Ni content than that of primary α phase. The residual primary α phase and MC carbides exist after (1 180 ℃, 4 h) solid-solution treatment especially in specimens with large section size. The plate-like secondary α phase and γ′-Ni3(Al, Ti, Nb) precipitate everywhere after (1 180 ℃, 4 h)+(900 ℃, 16 h) standard heat treatment. In addition, the granular M23C6 carbide further precipitates at grain boundary region, both of them can strengthen the alloy.
Key words: Ni-base superalloy; K4648; α-(Cr, Ni) phase; M23C6 carbide; microstructure
