CN103771837A

CN103771837A - Aluminum oxide/zirconium oxide SLM (selective laser melting) ceramic powder material and preparation method thereof

Info

Publication number: CN103771837A
Application number: CN201310753824.1A
Authority: CN
Inventors: 高勃; 刘治; 杨海鸥; 宋阚; 王伟娜; 吴江
Original assignee: Fourth Military Medical University FMMU
Current assignee: Fourth Military Medical University FMMU
Priority date: 2013-12-31
Filing date: 2013-12-31
Publication date: 2014-05-07
Anticipated expiration: 2033-12-31
Also published as: CN103771837B

Abstract

The invention relates to a novel Al2O3/ZrO2 powder material for SLM (selective laser melting) molding and a preparation method thereof. After molding by laser melting, the powder material forms an oral use Al2O3/ZrO2 composite ceramic material which has uniform internal tissue structure and has no obvious phase segregation. According to the preparation method, an electro-magnetic induction heating furnace and a laser are used for carry out secondary preheating on a powder bed, after achieving the preset preheating temperature, the powder material is molded by laser melting. The gradient of the interior temperature and the exterior temperature of a molten pool in molding of the ceramic material can be effectively reduced, the interior thermal stress can be lowered, cracks on the surface and in the interior of the material are reduced, and the mechanical property of the material is improved. The SLM Al2O3/ZrO2 composite ceramic material molded by the powder material through the preparation method has uniform internal tissues, has no phase segregation, has no obvious cracks on the surface and in the interior, has better mechanical property, and is expected to be used as a material of all-ceramic crown, bridge and inlay to be used in clinic of oral repair.

Description

Alumina-zirconia SLM ceramic powder material and preparation method thereof

Technical field

The present invention relates to selective laser melting and coating technique (Selective Laser Melting, SLM) processing ceramic Material Field, be specifically related to a kind of aluminum oxide (Al for oral cavity ₂o ₃)/zirconium white (ZrO ₂) diphase ceramic material powder with and the preparation method of SLM processing.

Background technology

Aluminum oxide (Al ₂o ₃) and zirconium white (ZrO ₂) composite ceramics reparation physical efficiency reproduction natural teeth color and luster, biology performance is good, can bear and chew more greatly load.The problems such as traditional fabrication mode adopts slip casting, glass infiltration sintering, exists technique loaded down with trivial details, and the process-cycle is long.At present main application dental CAD/CAM system, the mode that adopts numerical control cutting are removed after material machine-shaping sintering again to prefabricated machining ceramics base material.If adopt the high-strength ceramic of dense sintering as base material, its machinability is poor, and stock-removing efficiency is low, tool wear is large.In order to address these problems, the dental CAD/CAM system take Procera All-ceram as representative has adopted machining ceramic powder to press knot body or the method that partially sinters body is carried out machine-shaping, dummy is carried out fully sinteredly after cutting again, has reduced cutting difficulty.But cutting goes the mode of material processing to cause a large amount of wastes of material, has increased cost of manufacture; Meanwhile, press the preparation of knot body to need comparatively complicated equipment and process condition, and double sintering is time-consuming, effort, volumetric shrinkage when sintering is also fairly obvious, has affected the making precision of dummy.

Selective laser cladding (Selective Laser Melting, SLM) be a kind of advanced person's quick increasing material manufacturing technology, take powdered material as raw material, laser irradiation scanning can make powdered material fusing rapid solidification, under computer control, successively pile up moulding density and reach 100% part, not limited by structural complexity.The main advantage that it has is: 1. increase material manufacture, the utilization ratio of material is high; 2. once shaped, has reduced the step of process operation, has reduced cost and difficulty; 3. the processing mode of laser fast thawing rapid hardening has been given the formed material weave construction of uniformity and excellent mechanical property more.Because these advantages, SLM technology is applied to rapidly in the every field of materials processing, becomes at present the focus of research both at home and abroad.Chinese scholars can fast and low-cost utilize this fabrication techniques cochrome, pure titanium metal dummy, as substrate crown of removalbe partial denture bracket, ceramic prosthesis etc.But utilize the research of SLM technology processing ceramic material less, known research finds can exist component segregation and profiled member problems of crack, the mechanical property deficiency of forming ceramic part in the time carrying out ceramic forming material.

Summary of the invention

The defect or the deficiency that exist for above-mentioned prior art, the object of the invention is to, and a kind of Al for SLM moulding is provided ₂o ₃/ ZrO ₂powdered material and preparation method thereof.

In order to realize above-mentioned task, the present invention takes following technical solution:

A kind of Al for preparing moulding for SLM ₂o ₃/ ZrO ₂powdered material, is characterized in that, by Al ₂o ₃powder and ZrO ₂powder forms by mass percentage, Al ₂o ₃powder accounts for 62.5%, ZrO ₂powder accounts for 37.5%, wherein, and ZrO ₂in powder, be added with 2% Y ₂o ₃stablizer, this Al making ₂o ₃/ ZrO ₂powdered material D50 particle diameter is less than 100 μ m.

Above-mentioned Al ₂o ₃/ ZrO ₂the method that be processed into SLM ceramic block of powdered material on SLM equipment, is characterized in that, by Al ₂o ₃/ ZrO ₂powdered material is laid on pure Al ₂o ₃on substrate, single berth powder thickness is 500 μ m, and every one deck all adopts same procedure first to carry out preheating, and then carries out cladding forming.

Described preheating, the concrete steps of cladding forming are as follows:

1) paving powder equipment is placed on induction heater, is warming up to 1200 ℃ of left and right;

2) be 150W by laser power settings, spot diameter is 10mm, sweep velocity 4000mm/min, and be 1min warm up time, makes powder bed reach 1700 ℃ of desirable preheating temperatures;

3) step 2) finish after, adjust parameter, laser power is 200W, spot diameter is that 8mm sweep velocity is 10mm/min, carries out single track cladding forming;

4) after step 3) finishes, spread for the second time powder, paving powder thickness is 500 μ m, powder bed surface is struck off with scraper plate, then again according to step 1), step 2) order carries out the single track cladding forming of new one deck; Through repeatedly spreading powder, after single track cladding forming, form SLM ceramic block material.

Adopt Al of the present invention ₂o ₃/ ZrO ₂powdered material can be processed into SLM ceramic block, its interior tissue uniformity on SLM equipment, empty phase segregation, surface and inner without obviously crackle generation, mechanical property is better, be expected to be used as all-ceramic crown, the material of bridge and inlay is applied to oral repairing clinic.Solve the component segregation of prior art and the problem that crackle forms, finally laid the foundation for SLM technology is applied to full porcelain dummy making.

Accompanying drawing explanation

Fig. 1 is that A group powder mixes last ESM photo (50 times);

Fig. 2 is B group powder ESM photo photo (50 times);

Fig. 3 is C group powder ESM photo (100 times);

Fig. 4 is D group powder ESM photo (100 times);

Fig. 5 is different powder grouping test specimen vickers hardness number mean value histograms;

Fig. 6 is A group ESM photo (500 times);

Fig. 7 is B group ESM photo (500 times);

Fig. 8 is C group ESM photo (500 times);

Fig. 9 is B group SEM photo (longitudinal section, 1000 times);

Figure 10 is B group SEM photo (5000 times);

Figure 11 is that 1 energy spectrum analysis figure is put in clear zone;

Figure 12 is different powder mixture ratio grouping test specimen vickers hardness number mean value histograms;

Figure 13 is B group crystalline structure schematic perspective view;

Figure 14 is induction heater schematic diagram;

Figure 15 is experimental system schematic diagram;

Figure 16 is the photo of the SLM ceramic block material of moulding.

Figure 17 is a kind of structural representation that spreads powder equipment.

Below in conjunction with drawings and Examples, the present invention is described in further detail.

Embodiment

The present embodiment provides a kind of Al for preparing moulding for SLM ₂o ₃/ ZrO ₂powdered material, with Al ₂o ₃and ZrO ₂powder is raw material, according to mass percent preparation, Al ₂o ₃powder accounts for 62.5wt%, ZrO ₂powder accounts for 37.5wt%, wherein ZrO ₂powder contains the Y of 2wt% ₂o ₃stablizer, this Al making ₂o ₃/ ZrO ₂powdered material D50 particle diameter is less than 100 μ m.

By Al ₂o ₃/ ZrO ₂powdered material is processed into SLM ceramic block on SLM equipment, and every one deck all adopts same procedure first to carry out preheating, and then carries out cladding forming.

Below detailed research process:

Experimental system:

The structure of experimental system as shown in figure 15, comprises laser stereoforming equipment, induction heater and paving powder equipment, and paving powder equipment is arranged on induction heater.

Induction heater structural representation as shown in figure 14, comprises water cooled bottom plate 1(length 266mm), body of heater (height 165mm) on gland 5 and water cooled bottom plate 1, in body of heater, have refractory materials 4, body of heater periphery is wound with coil 2, coil 2 two ends tie cable joints 6.The height of induction heater is 225mm, and the internal diameter of burner hearth is 60mm, the in-built graphite 3 of burner hearth.

In test, applicant has made a kind of paving powder equipment, its structural representation as shown in figure 17, comprise base 7, above base 7, be placed with the substrate 8 with groove, be fixed with guide post 9 at 7 four angles of stainless steel base, above the substrate 8 with groove, be at least placed with the stainless steel plate 10 of a hollow by guide post 9.

The hollow position of stainless steel plate 10 is corresponding with the groove location of the substrate 8 with groove.The thickness of stainless steel plate 10 is identical or different.

Paving powder equipment principle of work is: every a slice stainless steel plate 10 is placed in the top with groove substrate 8, being equivalent to will band groove substrate 8(powder bed) corresponding decline one deck (floor height is determined by stainless steel plate thickness), the paving powder sintering of the hollow space of stainless steel plate can be realized to the upwards moulding of powdered material.Because stainless steel plate is fixed on above the groove of substrate by guide post all the time before moulding finishes, therefore there will not be caving in of powder bed in the course of processing, formed material is played to good supporting role.

In the present embodiment, laser stereoforming equipment adopts LSF III Type B laser stereoforming equipment, is provided by Northwestern Polytechnical University's state key solidification experiments chamber; When experiment, the laser apparatus in LSF III Type B laser stereoforming equipment is positioned at paving powder equipment top, carries out cladding forming under atmosphere protection condition.

Induction heater adopts GYDY-XASR induction heater, and rated output 30KW, is purchased from Xi'an three auspicious electric furnace company limited.

Experiment material:

Pure Al ₂o ₃substrate (70mm × 50mm × 20mm), is purchased from Materials Co., Ltd of Wuhan Xintai City;

Al ₂o ₃/ ZrO ₂powder (Al ₂o ₃account for 62.5wt%, ZrO ₂account for 37.5wt%), wherein ZrO ₂contain the Y of 2wt% ₂o ₃stablizer, powder D50 is < 100 μ m, by Beijing, Rui Fazhiyuan Science and Technology Ltd. provides by applicant's requirement.

Principle of design:

Al ₂o ₃and ZrO ₂eutectic ratio be 58.5wt%:41.5wt%, but applicant studies discovery, at the Al mixing according to this ratio ₂o ₃/ ZrO ₂mixed powder material inside organization structure after laser formation has produced obvious thing phase segregation, has the zirconium white crystal grain of volume particle size to separate out, and has affected the homogeneity that thing distributes mutually.Reason may be in laser cladding process, Al ₂o ₃boiling point lower (3000 ℃) and ZrO ₂boiling point relatively high (4300 ℃), part Al ₂o ₃after steam raising, break both eutectic ratios, in the time that both grow to aluminum oxide deficiency in eutectic ratio, just formed the zirconium white crystal grain of volume particle size and formed border with adjacent eutectic.Can make up the loss of aluminum oxide in SLM moulding process therefore selective oxidation al proportion is greater than the mixed powder of eutectic ratio, applicant finds the Al in mixed powder through overtesting ₂o ₃: ZrO ₂under the ratio condition of=62.5wt%:37.5wt%, compensate Al in laser cladding process ₂o ₃loss, the interior tissue thing of forming ceramic material is evenly distributed unanimously mutually.

Al ₂o ₃/ ZrO ₂the fusing point of eutectic material is 1860 ℃, research finds that the fast thawing rapid hardening process of laser melting coating can make the internal stress of stupalith excessive and cause the formation of crackle, and studies have found that and powder is heated to 200 ℃ of left and right under fusing point before laser melting coating, can significantly be lowered into the thermal stresses of shaped material inside, thereby the stupalith that molded surface and inner flawless generate, therefore adopted in the present embodiment first and carried out one-level preheating with induction heater, and then adopt laser to carry out the secondary preheating (temperature is lower than fusing point) of powder bed, reach the technological line that carries out again cladding forming after desirable preheating temperature.

Experiment is front to Al ₂o ₃substrate surface cleans decontamination with acetone after first polishing with No. 200 sand paper, by Al ₂o ₃/ ZrO ₂powder is laid on pure Al ₂o ₃on substrate, single berth powder thickness is 500 μ m, and every one deck all adopts same procedure first to carry out preheating, and then carries out cladding forming.

By pure Al ₂o ₃substrate is placed in the substrate top of paving powder equipment, is warming up to 1200 ℃ of left and right; Be 150W by laser power settings, spot diameter is 10mm, sweep velocity 4000mm/min, and be 1min warm up time, makes powder bed reach 1700 ℃ of preheating temperatures; Adjust parameter, laser power is 200W, and spot diameter is that 8mm sweep velocity is 10mm/min, carries out single track cladding forming; Re-start paving powder, paving powder thickness is 500 μ m, powder bed surface is struck off with scraper plate, and then above-mentioned steps order is carried out the moulding of new one deck again.Repeatedly spread powder, after moulding, form SLM ceramic block material (photo of the SLM ceramic block material of moulding is referring to Figure 16).

Applicant, in research process, has first studied the ceramic material powder of different grain size and pattern for the impact of microtexture and the mechanical property of laser formation material, and then optimizes the ceramic powder that is applicable to SLM processing.

Test method is: by 4 groups of different grain sizes and pattern Al2O3/ZrO2 powder grouping situation as table 1:

Table 1:Al ₂o ₃/ ZrO ₂mixed powder grouping situation

Powder grouping	D50 granularity	Pattern	Grinding mode
				A	＜1μm	Spherical	Atomization
B	＜1μm	Irregular	Comminution by gas stream
				C	＜100μm	Ball-type	Atomization
D	＜100μm	Sheet	Ball mill pulverizing

Under scanning electron microscope, observe powder morphology and globule size:

By 4 groups of powder uniform spreading powder, carry out the scanning of individual layer laser melting coating, laser power 500W, sweep velocity 30 μ m/s, spot diameter 5mm, thickness in monolayer 4mm, atmosphere is argon gas.Moulding SLM ceramic test piece is cut to embedding, polishing (80 order to 1200 order) and polishing, under scanning electron microscope, observe test specimen microtexture, energy spectrum analysis material forms, and each test specimen is chosen 6 points, and test microhardness (HV) is to evaluate its mechanical property.

Experimental result: referring to the vickers hardness number of 4 groups of raw material ceramic powder stereoscan photographs of Fig. 1 to Fig. 4 and 4 groups of powder compacting stupaliths of table 2 and Fig. 5.

Table 2: different powder grouping test specimen vickers hardness numbers (GPa)

Discussion of results: analyze from mechanical property, find that A, B group have shown compared with C, two groups of low hardness values of D, can say the low mechanical property of material, its reason may be that (< 1 μ m) because two groups of A, B are nanoscale powder, after paving powder, can produce agglomeration powder distribution density is differed, the place that when laser melting coating, powder loosens relatively easily produces defect and pore.A, two groups of powder of C be atomization ball-type powder but after moulding aspect the microtexture of material and hardness all with B, the D group of same particle sizes rank different-shape without obviously difference, can think under the condition of powder size indifference, structure and the performance of powder morphology to formed material has no significant effect.So ceramic powder material that we have selected powder that granularity is larger to prepare as SLM.

Secondly, applicant has studied Al ₂o ₃and ZrO ₂relation between the phase structure of the proportioning of mixed powder and formed material inside and distribution, acquisition can be prepared Al ₂o ₃/ ZrO ₂the proportioning raw materials of eutectic composite ceramics, and then solve the problem of the inner thing phase segregation of formed material.Experimental technique: the Al that chooses 3 kinds of different proportionings ₂o ₃and ZrO ₂mixed powder (wherein ZrO ₂in contain 5wt%Y ₂o ₃), grouping situation is as shown in table 3, ZrO in the A group in mixed powder ₂account for 37.5wt%, ZrO in B group ₂account for 42.5wt%, ZrO in C group ₂account for 47.5wt%.

Table 3:Al ₂o ₃/ ZrO ₂powder mixture ratio grouping (wt%)

?	ZrO ₂	Al ₂O ₃
			A	37.5	62.5
B	42.5	57.5
			C	47.5	52.5

After evenly mixing, carry out laser cladding forming, by scanning electron microscopic observation forming ceramic material microstructure; Utilize the microhardness of microhardness instrument test material.3 groups of different proportioning powder compacting 500 times of stereoscan photographs of material (transverse section) are referring to Fig. 6, Fig. 7 and Fig. 7.

1000 times of stereoscan photographs of B composing type material (longitudinal section) are referring to Fig. 9, and 5000 times of photos of B composing type material, referring to Figure 10, select clear zone point 1 to carry out energy spectrum analysis in Figure 10, obtain analytical results and see Figure 11; 3 composing type material microhardness values are referring to table 4 and Fig. 1.

Table 4: different powder mixture ratio grouping test specimen vickers hardness numbers (GPa)

Discussion of results: the fibrous ZrO in stereoscan photograph in visible A group material ₂crystal grain is at Al ₂o ₃in matrix, be evenly distributed, and there is obvious polynuclear plane in two groups of B, C, from B 1000 times of photos of group (Fig. 9), in 5000 times of (Figure 10) stereoscan photographs and EDAX results, can find that this structure separated out the ZrO2 crystal of volume particle size on border, can find that in conjunction with the longitudinal section photo of B group this is a kind of column eutectic structure (Figure 13) along scanning direction growth.

Research is found, can separate out the crystal of zirconium oxide of volume particle size under this conditions of mixture ratios, causes thing phase segregation.In A group, the ratio of aluminum oxide is greater than eutectic ratio, its thing more uniformity that distributes mutually, and without obviously thing phase segregation, surface and innerly generate without obvious crackle, mechanical property is better.And the ratio of aluminum oxide is more less than B group in C group, therefore also forms with B and organized identical structure.Hardness test has relatively proved the difference on three groups of materials microstructures, can think that the powder mixture ratio forming ceramic material of A group has the more thing of homogeneous to distribute mutually and better mechanical property.Be expected to be used as all-ceramic crown, the material of bridge and inlay is applied to oral repairing clinic.

Claims

1. the Al for SLM moulding ₂o ₃/ ZrO ₂powdered material, is characterized in that, by Al ₂o ₃powder and ZrO ₂powder forms by mass percentage, Al ₂o ₃powder accounts for 62.5%, ZrO ₂powder accounts for 37.5%, wherein, and ZrO ₂in powder, be added with 2% Y ₂o ₃stablizer, this Al making ₂o ₃/ ZrO ₂powdered material D50 particle diameter is less than 100 μ m.

2. the Al for SLM moulding claimed in claim 1 ₂o ₃/ ZrO ₂powdered material is processed into the method for SLM ceramic block on SLM equipment, it is characterized in that, by Al ₂o ₃/ ZrO ₂powdered material is laid on pure Al ₂o ₃on substrate, single berth powder thickness is 500 μ m, and every one deck all adopts same procedure first to carry out preheating, and then carries out cladding forming.

3. method as claimed in claim 2, is characterized in that, described preheating, the concrete steps of cladding forming are as follows:

(1) paving powder equipment is placed on induction heater, is warming up to 1200 ℃;

(2) be 150W by laser power settings, spot diameter is 10mm, sweep velocity 4000mm/min, and be 1min warm up time, the preheating temperature that makes powder bed is 1700 ℃;

(3) after step (2) finishes, adjustment laser power is 200W, and spot diameter is that 8mm sweep velocity is 10mm/min, carries out single track cladding forming;

(4) after step (3) finishes, spread for the second time powder, paving powder thickness is 500 μ m, powder bed surface is struck off with scraper plate, and then again according to step (1), step (2) order is carried out the single track cladding forming of new one deck; Through repeatedly spreading powder, after single track cladding forming, form SLM ceramic block material.