高密度合金薄壁构件等离子喷涂成形技术

对喷雾造粒高密度合金粉末进行1 600℃瞬时烧结处理,采用常压氩气保护等离子喷涂成形技术制备了壁厚≤5 mm的零部件,研究真空固相及液相烧结对喷涂成形件显微结构、致密度及力学性能的影响。结果表明:瞬时液相烧结后,喷雾造粒团聚体内的微细球磨粉末由机械混合转变为冶金结合,喷涂沉积率从45%提高至70%以上。等离子喷涂沉积层为层片结构,致密度约88.9%。经1 200和1 300℃真空固相烧结后,沉积层保持原始的层片结构,成形件拉伸强度随致密度升高而增大,其断口呈典型的沿晶断裂形貌,伸长率为零。经1 400℃液相烧结后,成形件仍表现为层片结构及沿晶脆性断裂形貌。经1 465℃烧结后,沉积层由层片结构转变为颗粒结构,成形件致密度显著提高至98.05%;断裂方式以沿晶断裂为主,穿晶断裂为辅;拉伸强度显著增大至567.10 MPa,伸长率达8.65%。

Plasma spray forming technology of near-net-shape thin-walled tungsten heavy alloy

95W-3.5Ni-1.5Fe composite feedstock fabricated by spray drying was instantaneously sintered at 1 600 ℃.Tungsten alloy with high density and wall thickness less than 5 mm were produced using plasma spray forming(PSF) followed by vacuum sintering at 1 200,1 300,1 400 and 1 465 ℃ for 90 min,respectively.After instantaneous sintering at 1 600 ℃,the ball milled fine particles of spray dried agglomerated powders transform from the mechanical bonding into the metallurgical bonding with deposition rate increasing from 45% to 70%.A typically lamellar structure is found in PSF deposits with the relative density of 88.90%.After sintering at 1 200 and 1 300 ℃ for 90 min,the initial lamellar structure is remained in the tested samples with increasing the relative density and ultimate tensile strength(UTS).The intergranular rupture can be found in fracture surfaces of deposits with no measurable elongation.The initial lamellar structure with dominated intergranular rupture is presented in the samples after sintering at 1 400 ℃ for 90 min.While sintering at 1 465 ℃,PSF deposits transform from lamellar structure into granular structure.The fracture surface of deposits is dominated by the mixture of intergranular rupture and transgranular rupture with UTS and elongation increase up to 567.10 MPa and 8.65%,respectively.